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High Energy Physics - Phenomenology (hep-ph) updates on the e-print archive
  • Thermal Dark Matter Through the Dirac Neutrino Portal. (arXiv:1709.07001v1 [hep-ph])

    Authors: Brian Batell, Tao Han, David McKeen, Barmak Shams Es Haghi

    We study a simple model of thermal dark matter annihilating to standard model neutrinos via the neutrino portal. A (pseudo-)Dirac sterile neutrino serves as a mediator between the visible and the dark sectors, while an approximate lepton number symmetry allows for a large neutrino Yukawa coupling and, in turn, efficient dark matter annihilation. The dark sector consists of two particles, a Dirac fermion and complex scalar, charged under a symmetry that ensures the stability of the dark matter. A generic prediction of the model is a sterile neutrino with a large active-sterile mixing angle that decays primarily invisibly. We derive existing constraints and future projections from direct detection experiments, colliders, rare meson and tau decays, electroweak precision tests, and small scale structure observations. Along with these phenomenological tests, we investigate the consequences of perturbativity and scalar mass fine tuning on the model parameter space. A simple, conservative scheme to confront the various tests with the thermal relic target is outlined, and we demonstrate that much of the cosmologically-motivated parameter space is already constrained. We also identify new probes of this scenario such as multi-body kaon decays and Drell-Yan production of $W$ bosons at the LHC.

  • Hidden Sector Dark Matter and the Galactic Center Gamma-Ray Excess: A Closer Look. (arXiv:1709.07002v1 [hep-ph])

    Authors: Miguel Escudero, Samuel J. Witte, Dan Hooper

    Stringent constraints from direct detection experiments and the Large Hadron Collider motivate us to consider models in which the dark matter does not directly couple to the Standard Model, but that instead annihilates into hidden sector particles which ultimately decay through small couplings to the Standard Model. We calculate the gamma-ray emission generated within the context of several such hidden sector models, including those in which the hidden sector couples to the Standard Model through the vector portal (kinetic mixing with Standard Model hypercharge), through the Higgs portal (mixing with the Standard Model Higgs boson), or both. In each case, we identify broad regions of parameter space in which the observed spectrum and intensity of the Galactic Center gamma-ray excess can easily be accommodated, while providing an acceptable thermal relic abundance and remaining consistent with all current constraints. We also point out that cosmic-ray antiproton measurements could potentially discriminate some hidden sector models from more conventional dark matter scenarios.

  • The Minimal Flavour Violating Axion. (arXiv:1709.07039v1 [hep-ph])

    Authors: F. Arias-Aragon, L. Merlo

    The solution to the Strong CP problem is analysed within the Minimal Flavour Violation (MFV) context. An Abelian factor of the complete flavour symmetry of the fermionic kinetic terms may play the role of the Peccei-Quinn symmetry in traditional axion models. Its spontaneous breaking, due to the addition of a complex scalar field to the Standard Model scalar spectrum, generates the MFV axion, which may redefine away the QCD theta parameter. It differs from the traditional QCD axion for its couplings that are governed by the fermion charges under the axial Abelian symmetry. It is also distinct from the so-called Axiflavon, as the MFV axion does not describe flavour violation, while it does induce flavour non-universality effects. The MFV axion phenomenology is discussed considering astrophysical, collider and flavour data.

  • Methods for deriving functional equations for Feynman integrals. (arXiv:1709.07058v1 [hep-ph])

    Authors: O. V. Tarasov

    We present short review of two methods for obtaining functional equations for Feynman integrals. Application of these methods for finding functional equations for one- and two- loop integrals is described in detail. It is shown that with the aid of functional equations Feynman integrals in general kinematics can be expressed in terms of simpler integrals. Similarities between functional equations for Feynman integrals and addition theorem for Abel integrals are shortly discussed.

  • Search for Nonstandard Neutrino Interactions with IceCube DeepCore. (arXiv:1709.07079v1 [hep-ex])

    Authors: IceCube Collaboration: M. G. Aartsen, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, I. Al Samarai, D. Altmann, K. Andeen, T. Anderson, I. Ansseau, G. Anton, C. Argüelles, J. Auffenberg, S. Axani, H. Bagherpour, X. Bai, J. P. Barron, S. W. Barwick, V. Baum, R. Bay, J. J. Beatty, J. Becker Tjus, K.-H. Becker, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, G. Binder, D. Bindig, E. Blaufuss, S. Blot, C. Bohm, M. Börner, F. Bos, D. Bose, S. Böser, O. Botner, E. Bourbeau, J. Bourbeau, F. Bradascio, J. Braun, L. Brayeur, M. Brenzke, H.-P. Bretz, S. Bron, J. Brostean-Kaiser, A. Burgman, T. Carver, J. Casey, M. Casier, E. Cheung, D. Chirkin, A. Christov, K. Clark, L. Classen, S. Coenders, G. H. Collin, J. M. Conrad, D. F. Cowen, R. Cross, M. Day, J. P. A. M. de André, et al. (257 additional authors not shown)

    As atmospheric neutrinos propagate through the Earth, vacuum-like oscillations are modified by Standard-Model neutral- and charged-current interactions with electrons. Theories beyond the Standard Model introduce heavy, TeV-scale bosons that can produce nonstandard neutrino interactions. These additional interactions may modify the Standard Model matter effect producing a measurable deviation from the prediction for atmospheric neutrino oscillations. The result described in this paper constrains nonstandard interaction parameters, building upon a previous analysis of atmospheric muon-neutrino disappearance with three years of IceCube-DeepCore data. The best fit for the muon to tau flavor changing term is $\epsilon_{\mu \tau}=-0.0005$, with a 90\% C.L. allowed range of $-0.0067 <\epsilon_{\mu \tau}< 0.0081$. This result is more restrictive than recent limits from other experiments for $\epsilon_{\mu \tau}$. Furthermore, our result is complementary to a recent constraint on $\epsilon_{\mu \tau}$ using another publicly available IceCube high-energy event selection. Together, they constitute the world's best limits on nonstandard interactions in the $\mu-\tau$ sector.

  • Axion as a non-WIMP dark matter candidate. (arXiv:1709.07091v1 [hep-ph])

    Authors: Ken'ichi Saikawa

    The axion arises in well-motivated extensions of the Standard Model of particle physics and is regarded as an alternative to the weakly interacting massive particle paradigm to explain the nature of dark matter. In this contribution, we review theoretical aspects of dark matter axions, particularly focusing on recent developments in the estimation of their relic abundance. A closer look at their non-thermal production mechanisms in the early universe reveals the possibility of explaining the observed dark matter abundance in various mass ranges. The mass ranges predicted in various cosmological scenarios are briefly summarized.

  • LHC limits on axion-like particles from heavy-ion collisions. (arXiv:1709.07110v1 [hep-ph])

    Authors: Simon Knapen, Tongyan Lin, Hou Keong Lou, Tom Melia

    In these proceedings we use recent LHC heavy-ion data to set a limit on axion-like particles coupling to electromagnetism with mass in the range 10-100 GeV. We recast ATLAS data as per the strategy proposed in 1607.06083, and find results in-line with the projections given there.

  • The $B \to \pi K$ Puzzle Revisited. (arXiv:1709.07142v1 [hep-ph])

    Authors: Nicolas Boisvert Beaudry, Alakabha Datta, David London, Ahmed Rashed, Jean-Samuel Roux

    For a number of years, there has been a certain inconsistency among the measurements of the branching ratios and CP asymmetries of the four $B \to \pi K$ decays ($B^+ \to \pi^+ K^0$, $B^+ \to \pi^0 K^+$, $B^0 \to \pi^- K^+$, $B^0 \to \pi^0 K^0$). In this paper, we re-examine this $B \to \pi K$ puzzle. We find that the key unknown parameter is $|C'/T'|$, the ratio of color-suppressed and color-allowed tree amplitudes. If this ratio is large, $|C'/T'| = 0.5$, the SM can explain the data. But if it is small, $|C'/T'| = 0.2$, the SM cannot explain the $B \to \pi K$ puzzle -- new physics (NP) is needed. The two types of NP that can contribute to $B \to \pi K$ at tree level are $Z'$ bosons and diquarks. $Z'$ models can explain the puzzle if the $Z'$ couples to right-handed $u{\bar u}$ and/or $d{\bar d}$, with $g_R^{dd} \ne g_R^{uu}$. Interestingly, half of the many $Z'$ models proposed to explain the present anomalies in $b \to s \mu^+ \mu^-$ decays have the required $Z'$ couplings to $u{\bar u}$ and/or $d{\bar d}$. Such models could potentially explain both the $b \to s \mu^+ \mu^-$ anomalies and the $B \to \pi K$ puzzle. The addition of a color sextet diquark that couples to $ud$ can also explain the puzzle.

  • Regge-like relation and universal description of heavy-light systems. (arXiv:1709.07196v1 [hep-ph])

    Authors: Kan Chen, Yubing Dong, Xiang Liu, Qi-Fang Lü, Takayuki Matsuki

    Using the Regge-like formula $(M-m_Q)^2=\pi\sigma L$ between hadron mass $M$ and angular momentum $L$ with a heavy quark mass $m_Q$ and a string tension $\sigma$, we analyze all the heavy-light systems, i.e., $D/D_s/B/B_s$ mesons and charmed and bottom baryons. Numerical plots are obtained for all the heavy-light mesons of experimental data whose slope becomes nearly equal to 1/2 of that for light hadrons. Assuming that charmed and bottom baryons consist of one heavy quark and one light cluster of two light quarks (diquark), we apply the formula to all the heavy-light baryons including recently discovered $\Omega_c$'s and find that all the heavy-light baryons experimentally measured satisfy the above formula. We predict the average mass values of $B$, $B_s$, $\Lambda_b$, $\Sigma_c$, $\Xi_c$, and $\Omega_c$ with $L=2$ as 6.009, 6.129, 6.145, 3.053, 3.068, and 3.338 GeV, respectively. Our results on baryons suggest that these baryons can be safely regarded as heavy quark-light cluster configuration. We also find a universal description for all the heavy-light mesons as well as baryons, i.e., one unique line is enough to describe both of charmed and bottom heavy-light systems.

  • Implication of Quadratic Divergences Cancellation in the Two Higgs Doublet Model. (arXiv:1709.07219v1 [hep-ph])

    Authors: Neda Darvishi, Maria Krawczyk

    With the aim of exploring the Higgs sector of the Two Higgs Doublet Model (2HDM), we have chosen the exact and soft $Z_2$ symmetry breaking versions of the 2HDM with non-zero vacuum expectation values for both Higgs doublets (Mixed Model). We consider two SM-like scenarios: with 125 GeV $h$ and 125 GeV $H$. We have applied the condition for cancellation of quadratic divergences in the type II 2HDM in order to derive masses of the heavy scalars. Solutions of two relevant conditions were found in the considered SM-like scenarios. After applying the current LHC data for the observed 125 GeV Higgs boson, the precision electroweak data test and lower limits on the mass of $H^+$, the allowed region of parameters shrink strongly.

  • The hadronic interaction model SIBYLL 2.3c and Feynman scaling. (arXiv:1709.07227v1 [hep-ph])

    Authors: Felix Riehn, Hans P. Dembinski, Ralph Engel, Anatoli Fedynitch, Thomas K. Gaisser, Todor Stanev

    The Monte Carlo model Sibyll has been designed for efficient simulation of hadronic multiparticle production up to the highest energies as needed for interpreting cosmic ray measurements. For more than 15 years, version 2.1 of Sibyll has been one of the standard models for air shower simulation. Motivated by data of LHC and fixed-target experiments and a better understanding of the phenomenology of hadronic interactions, we have developed an improved version of this model, version 2.3, which has been released in 2016. In this contribution we present a revised version of this model, called Sibyll 2.3c, that is further improved by adjusting particle production spectra to match the expectation of Feynman scaling in the fragmentation region. After a brief introduction to the changes implemented in Sibyll 2.3 and 2.3c with respect to Sibyll 2.1, the current predictions of the model for the depth of shower maximum, the number of muons at ground, and the energy spectrum of muons in extensive air showers are presented.

  • Role of QCD compositeness in the production of scalar and tensor mesons through single-photon annihilation $e^+ e^- \to \gamma^* \to \gamma S(T)$. (arXiv:1709.07234v1 [hep-ph])

    Authors: Alexandr G. Chumakov, Thomas Gutsche, Valery E. Lyubovitskij, Ivan Schmidt

    We study the exclusive production of scalar $S = 0^{++}$ and tensor $T = 2^{++}$ mesons through single-photon annihilation $e^+ e^- \to \gamma^* \to \gamma S(T)$. Using QCD compositeness of the involved hadrons considered as quark-antiquark systems, the prediction for the scaling of the differential cross sections of these processes is $d\sigma/dt \sim 1/s^3$ at large $s$. We further derive the scaling of the $\gamma^\ast \to \gamma S$ and $\gamma^\ast \to \gamma T$ transition form factors: $F_{\gamma^\ast\gamma S}(s) \sim 1/s$ and $F_{\gamma^\ast\gamma T}(s) \sim 1/s^2$. Results for the respective cross sections of the scalar meson production are presented. Also we test a possible tetraquark structure of the $f_0(980)$ and $a_0(980)$. When these states are tetraquark systems of two tightly bound color diquarks, the corresponding transition form factors and differential cross sections have the same falloffs as in the case of quark-antiquark picture. For other tetraquark configurations the transition form factors $F_{\gamma^\ast\gamma S(T)}(s)$ and the differential cross section $d\sigma/dt$ have additional $1/s$ and $1/s^2$ falloffs, respectively.

  • The effect of profiling procedure on PDFs using LHCb data. (arXiv:1709.07247v1 [hep-ph])

    Authors: A. Aleedaneshvar, Ali N. Khorramian

    The heavy-flavour production at forward rapidity in $pp$ collisions at the LHC is a very useful tool to assess the gluon density at low momentum fraction $x$. In this work, the impact of heavy-flavour measurements of the LHCb at center-of-mass energy of $ \sqrt s= $7 TeV on parton distribution functions (PDFs) is studied. To this aim, the normalised LHCb cross sections of charm and beauty hadron production are included into two modern PDF sets CT14 and MMHT using the PDF profiling procedure. It is illustrated that the LHCb data impose tighter constraints on the gluon distributions at low $x$, down to $x \sim 10^{-6}$, the region that is currently not covered by other experimental data which CT14 and MMHT have used in their perturbative QCD fits. We also affirm that the LHCb data will affect the MMHT gluon distribution more than the CT14 one, if they are included in their global analyses.

  • Determination of the strong coupling constant $\alpha_s(M_Z)$ in next-to-next-to-leading order QCD using H1 jet cross section measurements. (arXiv:1709.07251v1 [hep-ex])

    Authors: H1 collaboration: V. Andreev, A. Baghdasaryan, K. Begzsuren, A. Belousov, V. Bertone, A. Bolz, V. Boudry, G. Brandt, V. Brisson, D. Britzger, A. Buniatyan, A. Bylinkin, L. Bystritskaya, A.J. Campbell, K.B. Cantun Avila, K. Cerny, V. Chekelian, J.G. Contreras, J. Cvach, J. Currie, J.B. Dainton, K. Daum, C. Diaconu, M. Dobre, V. Dodonov, G. Eckerlin, S. Egli, E. Elsen, L. Favart, A. Fedotov, J. Feltesse, M. Fleischer, A. Fomenko, E. Gabathuler, J. Gayler, T. Gehrmann, S. Ghazaryan, L. Goerlich, N. Gogitidze, M. Gouzevitch, C. Grab, A. Grebenyuk, T. Greenshaw, G. Grindhammer, C. Gwenlan, D. Haidt, R.C.W. Henderson, J. Hladky, D. Hoffmann, R. Horisberger, T. Hreus, F. Huber, A. Huss, M. Jacquet, X. Janssen, A.W. Jung, H. Jung, M. Kapichine, J. Katzy, C. Kiesling, M. Klein, C. Kleinwort, R. Kogler, et al. (84 additional authors not shown)

    The strong coupling constant $\alpha_s(M_Z)$ is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic $ep$ scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of $\alpha_s(M_Z)$ at the $Z$-boson mass $m_Z$ are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be $\alpha_s(M_Z)=0.1157\,(20)_{\rm exp}\,(29)_{\rm th}$. Complementary, \asmz\ is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $\alpha_s(M_Z)=0.1142\,(28)_{\rm tot}$ obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.

  • Upper bound on the Abelian gauge coupling from asymptotic safety. (arXiv:1709.07252v1 [hep-th])

    Authors: Astrid Eichhorn, Fleur Versteegen

    We explore the impact of asymptotically safe quantum gravity on the Abelian gauge coupling in a model including a charged scalar, confirming indications that asymptotically safe quantum fluctuations of gravity could trigger a power-law running towards a free fixed point for the gauge coupling above the Planck scale. Simultaneously, quantum gravity fluctuations balance against matter fluctuations to generate an interacting fixed point, which acts as a boundary of the basin of attraction of the free fixed point. This enforces an upper bound on the infrared value of the Abelian gauge coupling. In the regime of gravity couplings which in our approximation also allows for a prediction of the top quark and Higgs mass close to the experimental value [1], we obtain an upper bound approximately 35% above the infrared value of the hypercharge coupling in the Standard Model.

  • The $D\bar{D}^*$ interaction with isospin zero in an extended hidden gauge symmetry approach. (arXiv:1709.07263v1 [hep-ph])

    Authors: Bao-Xi Sun, Da-Ming Wan, Si-Yu Zhao

    The $D \bar{D}^*$ interaction via a $\rho$ or $\omega$ exchange is constructed within an extended hidden gauge symmetry approach, where the strange quark is replaced by the charm quark in the $SU(3)$ flavor space. With this $D \bar{D}^*$ interaction, a resonance state slightly above the $D \bar{D}^*$ threshold is generated dynamically in the isospin zero sector by solving the Bethe-Salpeter equation in the coupled-channel approximation, which might correspond to the $X(3872)$ particle announced by many collaborations. This formulism is also used to study the $B \bar{B}^*$ interaction, and a resonance state with isospin zero is generated dynamically, which has no counterpart listed in the review of the Particle data group. Furthermore, the one pion exchange between the $D$ meson and the $\bar{D}^*$ is analyzed precisely, and we do not think the one pion exchange potential need to be considered when the Bethe-Salpeter equation is solved.

  • Cold light dark matter in extended seesaw models. (arXiv:1709.07283v1 [hep-ph])

    Authors: Sami Boulebnane, Julian Heeck, Anne Nguyen, Daniele Teresi

    We present a thorough discussion of light dark matter produced via freeze-in in two-body decays A -> B DM. If A and B are quasi-degenerate, the dark matter particle has a cold spectrum even for sub-keV masses. We show this explicitly by calculating the transfer function that encodes the impact on structure formation. As examples for this setup we study extended seesaw mechanisms with a spontaneously broken global U(1) symmetry, such as the inverse seesaw. The eV-keV-scale pseudo-Goldstone dark matter particle is then naturally produced cold by the decays of the quasi-degenerate right-handed neutrinos.

  • Bound on dissipative effects from semileptonic neutral B-meson decays. (arXiv:1709.07313v1 [hep-ph])

    Authors: F. Benatti, R. Floreanini, S. Marcantoni, P. Pinotti, K. Zimmermann

    The semileptonic decay asymmetry $\mathcal{A}_{\Delta m}$ is studied within the open quantum systems approach to the physics of the neutral meson $B^0$-$\overline{B^0}$ system: this extended treatment takes into account possible non-standard, dissipative effects induced by the presence of an external environment. A bound on these effects is provided through the analysis of available experimental data from the Belle Collaboration.

  • Momentum distribution of particles created in space-time-dependent colliding laser pulses. (arXiv:1709.07331v1 [hep-ph])

    Authors: I. A. Aleksandrov, G. Plunien, V. M. Shabaev

    We study the pair-production process in the presence of two counterpropagating linearly polarized short laser pulses. By means of a nonperturbative technique, we take into account the full coordinate dependence of the external field going beyond the dipole and standing-wave approximations. In particular, we analyze the momentum distribution of particles created. It is demonstrated that the spatial variations of the laser pulses may play a crucial role. The more accurate treatment reveals a number of prominent features: the pair-production probabilities become considerably smaller, the quantitative behavior of the momentum spectra changes dramatically, and the pulse shape effects become much less pronounced. The results of our study are expected to be very important for future theoretical and experimental investigations.

  • The running coupling from gluon and ghost propagators in the Landau gauge: Yang-Mills theories with adjoint fermions. (arXiv:1709.07367v1 [hep-lat])

    Authors: Georg Bergner, Stefano Piemonte

    Non-Abelian gauge theories with fermions transforming in the adjoint representation of the gauge group (AdjQCD) are a fundamental ingredient of many models that describe the physics beyond the Standard Model. Two relevant examples are N=1 Supersymmetric Yang-Mills (SYM) theory and Minimal Walking Technicolor, which are gauge theories coupled to one adjoint Majorana and two adjoint Dirac fermions, respectively. While confinement is a property of N=1 SYM, Minimal Walking Technicolor is expected to be infrared conformal. We study the propagators of ghost and gluon fields in the Landau gauge to compute the running coupling in the MiniMom scheme. We analyze several different ensembles of lattice Monte Carlo simulations for the SU(2) adjoint QCD with Nf=1/2, 1, 3/2, and 2 Dirac fermions. We show how the running of the coupling changes as the number of interacting fermions is increased towards the conformal window.

  • On the precise determination of the Tsallis parameters in proton - proton collisions at LHC energies. (arXiv:1709.07376v1 [hep-ph])

    Authors: T. Bhattacharyya, J. Cleymans, L. Marques, S. Mogliacci, M.W. Paradza

    A detailed analysis is presented about the precise values of the Tsallis parameters obtained in $p-p$ collisions for identified particles, pions, kaons and protons at the LHC at three beam energies $\sqrt{s} = 0.9, 2.72$ and $7$ TeV. Interpolated data at $\sqrt{s} = $ 5.02 TeV have also been included. It is shown that the Tsallis formula provides very good fits to the $p_T$ distributions in $p-p$ collisions at the LHC using three parameters $dN/dy$, $T$ and $q$. However, the parameters $T$ and $q$ depend on the particle species and are different for pions, kaons and protons. As a consequence there is no $m_T$ scaling and also no universality of the parameters for different particle species.

  • Dark Matter Annihilation into Four-Body Final States and Implications for the AMS Antiproton Excess. (arXiv:1709.07410v1 [astro-ph.HE])

    Authors: Steven J. Clark, Bhaskar Dutta, Louis E. Strigari

    We consider dark matter annihilation into a general set of final states of Standard Model particles, including two-body and four-body final states that result from the decay of intermediate states. For dark matter masses ~10-10^5 GeV, we use updated data from Planck and from high gamma-ray experiments such as Fermi-LAT, MAGIC, and VERITAS to constrain the annihilation cross section for each final state. The Planck constraints are the most stringent over the entire mass range for annihilation into light leptons, and the Fermi-LAT constraints are the most stringent for four-body final states up to masses ~10^4 GeV. We consider these constraints in light of the recent AMS antiproton results, and show that for light mediators it is possible to explain the AMS data with dark matter, and remain consistent with Fermi-LAT Inner Galaxy measurements, for m_\chi ~ 60-100 GeV mass dark matter and mediator masses m_\phi / m_\chi ~< 1.

  • New low-$Q^2$ measurements of the $\gamma^\ast N \to \Delta(1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem. (arXiv:1709.07412v1 [hep-ph])

    Authors: G. Ramalho

    The novel measurements of the $\gamma^\ast N \to \Delta(1232)$ Coulomb quadrupole form factor in the range $Q^2=0.04$--0.13 GeV$^2$ changed the trend of the previous data. With the new data the electric and Coulomb form factors are both in remarkable agreement with estimates of the pion cloud contributions to the quadrupole form factors at low $Q^2$. The pion cloud contributions to the electric and Coulomb form factors can be parametrized by the relations $G_E \propto G_{En}/\left(1 + \frac{Q^2}{2M_\Delta(M_\Delta-M)}\right)$ and $G_C \propto G_{En}$, where $G_{En}$ is the neutron electric form factor, and $M$, $M_\Delta$ are the nucleon and $\Delta$ masses, respectively. Those parametrizations are in full agreement with Siegert's theorem, which states that $G_E= \frac{M_\Delta-M}{2M_\Delta} G_C$ at the pseudothreshold, when $Q^2=-(M_\Delta -M)^2$, and improve previous parametrizations. For this agreement contributes also a small valence quark effects component estimated by a covariant quark model. The combination of the new data with the new parametrization for $G_E$ culminates an intense period of studying the $\gamma^\ast N \to \Delta(1232)$ quadrupole form factors at low $Q^2$, with the agreement between theory and data.

  • Global extraction of the parton-to-kaon fragmentation functions at NLO in QCD. (arXiv:1709.07415v1 [hep-ph])

    Authors: R. J. Hernández-Pinto, M. Epele, D. de Florian, R. Sassot, M. Stratmann

    In this document, we present the global QCD analysis of parton-to-kaon fragmentation functions at next-to-leading order accuracy using the latest experimental information on single-inclusive kaon production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An extended analysis of this work can be found in Ref.[1].

  • A Comprehensive Renormalisation Group Analysis of the Littlest Seesaw Model. (arXiv:1709.07425v1 [hep-ph])

    Authors: Tanja Geib, Stephen F. King

    We present a comprehensive renormalisation group analysis of the Littlest Seesaw model involving two right-handed neutrinos and a very constrained Dirac neutrino Yukawa coupling matrix. We perform the first $\chi^2$ analysis of the low energy masses and mixing angles, in the presence of renormalisation group corrections, for various right-handed neutrino masses and mass orderings, both with and without supersymmetry. We find that the atmospheric angle, which is predicted to be near maximal in the absence of renormalisation group corrections, may receive significant corrections for some non-supersymmetric cases, bringing it into close agreement with the current best fit value in the first octant. By contrast, in the presence of supersymmetry, the renormalisation group corrections are relatively small, and the prediction of a near maximal atmospheric mixing angle is maintained, for the studied cases. Forthcoming results from T2K and NOvA will decisively test these models at a precision comparable to the renormalisation group corrections we have calculated.

  • Implications of GW related searches for IceCube. (arXiv:1709.07430v1 [astro-ph.HE])

    Authors: Krijn D. de Vries, Gwenhaël de Wasseige, Jean-Marie Frère, Matthias Vereecken

    At the beginning of 2016, LIGO reported the first-ever direct detection of gravitational waves. The measured signal was compatible with the merger of two black holes of about 30 solar masses, releasing about 3 solar masses of energy in gravitational waves. We consider the possible neutrino emission from a binary black hole merger relative to the energy released in gravitational waves and investigate the constraints coming from the non-detection of counterpart neutrinos, focusing on IceCube and its energy range. The information from searches for counterpart neutrinos is combined with the diffuse astrophysical neutrino flux in order to put bounds on neutrino emission from binary black hole mergers. Prospects for future LIGO observation runs are shown and compared with model predictions.

  • Master integrals for the NNLO virtual corrections to $\mu e$ scattering in QED: the planar graphs. (arXiv:1709.07435v1 [hep-ph])

    Authors: Pierpaolo Mastrolia, Massimo Passera, Amedeo Primo, Ulrich Schubert

    We evaluate the master integrals for the two-loop, planar box-diagrams contributing to the elastic scattering of muons and electrons at next-to-next-to leading-order in QED. We adopt the method of differential equations and the Magnus exponential series to determine a canonical set of integrals, finally expressed as a Taylor series around four space-time dimensions, with coefficients written as combination of generalised polylogarithms. The electron is treated as massless, while we retain full dependence on the muon mass. The considered integrals are also relevant for crossing-related processes, such as di-muon production at $e^+ e^-$-colliders, as well as for the QCD corrections to $top$-pair production at hadron colliders.

  • Safe SUSY. (arXiv:1709.07436v1 [hep-th])

    Authors: Borut Bajc, Nicola Andrea Dondi, Francesco Sannino

    We investigate the short distance fate of distinct classes of not asymptotically free supersymmetric gauge theories. Examples include super QCD with two adjoint fields and generalised superpotentials, gauge theories without superpotentials and with two types of matter representation and quiver theories. We show that an asymptotically safe scenario is nonperturbatively compatible with all known constraints.

  • Muonic hydrogen and the proton size. (arXiv:1709.07440v1 [hep-ph])

    Authors: Wayne W. Repko, Duane A. Dicus

    We reexamine the structure of the $n=2$ levels of muonic hydrogen using a two-body potential that includes all relativistic and one loop corrections. The potential was originally derived from QED to describe the muonium atom and accounts for all contributions to order $\alpha^5$. Since one loop corrections are included, the anomalous magnetic moment contributions of the muon can be identified and replaced by the proton anomalous magnetic moment to describe muonic hydrogen with a point-like proton. This serves as a convenient starting point to include the dominant electron vacuum polarization corrections to the spectrum and extract the proton's mean squared radius $\langle r^2\rangle$. Our results are consistent with other theoretical calculations that find that the muonic hydrogen value for $\langle r^2\rangle$ is smaller than the result obtained from electron scattering.

  • Baryogenesis in false vacuum. (arXiv:1605.06897v4 [hep-ph] UPDATED)

    Authors: Yuta Hamada, Masatoshi Yamada

    The null result in the LHC may indicate that the standard model is not drastically modified up to very high scales such as the GUT/string scale. Having this in the mind, we suggest a novel leptogenesis scenario realized in the false vacuum of the Higgs field. If the Higgs field develops a large vacuum expectation value in the early universe, a lepton number violating process is enhanced, which we use for baryogenesis. To demonstrate the scenario, several models are discussed. For example, we show that the observed baryon asymmetry is successfully generated in the standard model with higher-dimensional operators.

  • BFKL phenomenology: resummation of high-energy logs in semi-hard processes at LHC. (arXiv:1606.07327v3 [hep-ph] UPDATED)

    Authors: Francesco Giovanni Celiberto

    A study of differential cross sections and azimuthal observables for semi-hard processes at LHC energies, including BFKL resummation effects, is presented. Particular attention has been paid to the behaviour of the azimuthal correlation momenta, when a couple of forward/backward jets or identified hadrons is produced in the final state with a large rapidity separation. Three- and four- jet production has been also considered, the main focus lying on the definition of new, generalized azimuthal observables, whose dependence on the transverse momenta and the rapidities of the central jet(s) can be considered as a distinct signal of the onset of BFKL dynamics.

  • Searching for Dark Absorption with Direct Detection Experiments. (arXiv:1608.02123v3 [hep-ph] UPDATED)

    Authors: Itay M. Bloch, Rouven Essig, Kohsaku Tobioka, Tomer Volansky, Tien-Tien Yu

    We consider the absorption by bound electrons of dark matter in the form of dark photons and axion-like particles, as well as of dark photons from the Sun, in current and next-generation direct detection experiments. Experiments sensitive to electron recoils can detect such particles with masses between a few eV to more than 10 keV. For dark photon dark matter, we update a previous bound based on XENON10 data and derive new bounds based on data from XENON100 and CDMSlite. We find these experiments to disfavor previously allowed parameter space. Moreover, we derive sensitivity projections for SuperCDMS at SNOLAB for silicon and germanium targets, as well as for various possible experiments with scintillating targets (cesium iodide, sodium iodide, and gallium arsenide). The projected sensitivity can probe large new regions of parameter space. For axion-like particles, the same current direction detection data improves on previously known direct-detection constraints but does not bound new parameter space beyond known stellar cooling bounds. However, projected sensitivities of the upcoming SuperCDMS SNOLAB using germanium can go beyond these and even probe parameter space consistent with possible hints from the white dwarf luminosity function. We find similar results for dark photons from the sun. For all cases, direct-detection experiments can have unprecedented sensitivity to dark-sector particles.

  • Multi-Boson Interactions at the LHC. (arXiv:1610.07572v2 [hep-ex] UPDATED)

    Authors: Daniel R. Green, Patrick Meade, Marc-Andre Pleier

    This review covers results on the production of all possible electroweak boson pairs and 2-to-1 vector boson fusion at the CERN Large Hadron Collider (LHC) in proton-proton collisions at a center of mass energy of 7 and 8 TeV. The data were taken between 2010 and 2012. Limits on anomalous triple gauge couplings (aTGCs) then follow. In addition, data on electroweak triple gauge boson production and 2-to-2 vector boson scattering yield limits on anomalous quartic gauge boson couplings (aQGCs). The LHC hosts two general purpose experiments, ATLAS and CMS, which have both reported limits on aTGCs and aQGCs which are herein summarized. The interpretation of these limits in terms of an effective field theory is reviewed, and recommendations are made for testing other types of new physics using multi-gauge boson production.

  • A phenomenological study on the production of Higgs bosons in the cSMCS model at the LHC. (arXiv:1611.03312v2 [hep-ph] UPDATED)

    Authors: Neda Darvishi, Mohammad Reza Masouminia

    In the present work, we intend to predict the production rates of the Higgs bosons in the simplest extension of the Standard Model (SM) by a neutral complex singlet (cSMCS). This model has an additional source of CP violation and provides strong enough first-order electroweak phase transition to generate the baryon asymmetry of universe (BAU). The scalar spectrum of the cSMCS includes three neutral Higgs particles with the lightest one considered to be the 125 GeV Higgs boson found at LHC. The SM-like Higgs boson comes mostly from the SM-like SU(2) doublet, with a small correction from the singlet. To predict the production rates of the Higgs bosons, we use a conventional effective LO QCD framework and the unintegrated parton distribution functions (UPDF) of Kimber-Martin-Ryskin (KMR). We first compute the SM Higgs production cross-section and compare the results to the existing theoretical calculations from different frameworks as well as the experimental data from the CMS and ATLAS collaborations. It is shown that our framework is capable of producing sound predictions for these high-energy QCD events in the SM. Afterwards we present our predictions for the Higgs boson production in the cSMCS.

  • Prediction on the CP phases in Standard Model. (arXiv:1612.02891v4 [hep-ph] UPDATED)

    Authors: Chilong Lin

    In this article, a Yukawa coupling pattern in standard model is proposed and diagonalized analytically. Unitary transformation matrices thus derived lead to a CKM matrix with complex elements. However, the magnitudes of CKM elements thus derived do not match empirical values perfectly at tree level. Phenomenologically, several fine-tuning parameters are employed and that fits all CKM elements with empirical values to ${\bf O}(10^{-4})$. Furthermore, a set of Yukawa coupling parameters are numerically achieved and thus, CP-violating phases in $V_{CKM}$ are predicted.

  • Forward two-photon exchange in elastic lepton-proton scattering and hyperfine-splitting correction. (arXiv:1701.05514v5 [hep-ph] UPDATED)

    Authors: Oleksandr Tomalak

    We relate the forward two-photon exchange (TPE) amplitudes to integrals of the inclusive lepton-proton scattering cross sections. These relations yield an alternative way for the evaluation of the TPE correction to hyperfine-splitting (HFS) in the hydrogen-like atoms with an equivalent to the standard approach (Iddings, Drell and Sullivan) result implying the Burkhardt-Cottingham sum rule. For evaluation of the individual effects (e.g., elastic contribution) our approach yields a distinct result. We compare both methods numerically on examples of the elastic contribution and the full TPE correction to HFS in electronic and muonic hydrogen.

  • How light a higgsino or a wino dark matter can become in a compressed scenario of MSSM. (arXiv:1702.03954v2 [hep-ph] UPDATED)

    Authors: Manimala Chakraborti, Utpal Chattopadhyay, Sujoy Poddar

    Higgsinos and Wino have strong motivations for being Dark Matter (DM) candidates in supersymmetry, but their annihilation cross sections are quite large. For thermal generation and a single component DM setup the higgsinos or wino may have masses of around 1 or 2-3 TeV respectively. For such DM candidates, a small amount of slepton coannihilation may decrease the effective DM annihilation cross section. This, in turn reduces the lower limit of the relic density satisfied DM mass by more than 50%. Almost a similar degree of reduction of the same limit is also seen for squark coannihilations. However, on the contrary, for near degeneracy of squarks and higgsino DM, near its generic upper limit, the associated coannihilations may decrease the relic density, thus extending the upper limit towards higher DM masses. We also compute the direct and indirect detection signals. Here, because of the quasi-mass degeneracy of the squarks and the LSP, we come across a situation where squark exchange diagrams may contribute significantly or more strongly than the Higgs exchange contributions in the spin-independent direct detection cross section of DM. For the higgsino-DM scenario, we observe that a DM mass of 600 GeV to be consistent with WMAP/PLANCK and LUX data for sfermion coannihilations. The LUX data itself excludes the region of 450 to 600 GeV, by a half order of magnitude of the cross-section, well below the associated uncertainty. The similar combined lower limit for a wino DM is about 1.1 TeV. There is hardly any collider bound from the LHC for squarks and sleptons in such a compressed scenario where sfermion masses are close to the mass of a higgsino/wino LSP.

  • Asymmetric thermal-relic dark matter: Sommerfeld-enhanced freeze-out, annihilation signals and unitarity bounds. (arXiv:1703.00478v2 [hep-ph] UPDATED)

    Authors: Iason Baldes, Kalliopi Petraki

    Dark matter that possesses a particle-antiparticle asymmetry and has thermalised in the early universe, requires a larger annihilation cross-section compared to symmetric dark matter, in order to deplete the dark antiparticles and account for the observed dark matter density. The annihilation cross-section determines the residual symmetric component of dark matter, which may give rise to annihilation signals during CMB and inside haloes today. We consider dark matter with long-range interactions, in particular dark matter coupled to a light vector or scalar force mediator. We compute the couplings required to attain a final antiparticle-to-particle ratio after the thermal freeze-out of the annihilation processes in the early universe, and then estimate the late-time annihilation signals. We show that, due to the Sommerfeld enhancement, highly asymmetric dark matter with long-range interactions can have a significant annihilation rate, potentially larger than symmetric dark matter of the same mass with contact interactions. We discuss caveats in this estimation, relating to the formation of stable bound states. Finally, we consider the non-relativistic partial-wave unitarity bound on the inelastic cross-section, we discuss why it can be realised only by long-range interactions, and showcase the importance of higher partial waves in this regime of large inelasticity. We derive upper bounds on the mass of symmetric and asymmetric thermal-relic dark matter for s-wave and p-wave annihilation, and exhibit how these bounds strengthen as the dark asymmetry increases.

  • Charged-Higgs on $R_{D^{(*)}}$, $\tau$ polarization, and FBA. (arXiv:1703.03646v2 [hep-ph] UPDATED)

    Authors: Chuan-Hung Chen, Takaaki Nomura

    We study the influence of a charged-Higgs on the excess of branching fraction ratio, $R_M = BR(\bar B \to M \tau \bar\nu_\tau)/BR(\bar B \to M \ell \bar \nu_\ell)$ $(M=D, D^*)$, in a generic two-Higgs-doublet model. In order to investigate the lepton polarization, the detailed decay amplitudes with lepton helicity are given. When the charged-Higgs is used to resolve excesses, it is found that two independent Yukawa couplings are needed to explain the $R_D$ and $R_{D^*}$ anomalies. We show that when the upper limit of $BR(B_c \to \tau \bar \nu_\tau)<30\%$ is included, $R_D$ can be significantly enhanced while $R_{D^*}<0.27$. With the $BR(B_c\to \tau \bar \nu_\tau)$ constraint, we find that the $\tau$-lepton polarizations can be still affected by the charged-Higgs effects, where the standard model (SM) predictions are obtained as: $P^\tau_{D} \approx 0.324$ and $P^\tau_{D^*}\approx -0.500$, and they can be enhanced to be $P^\tau_{D} \approx 0.5$ and $P^\tau_{D^*} \approx -0.41$ by the charged-Higgs. The integrated lepton froward-backward asymmetry (FBA) is also studied, where the SM result is $\bar A^{D^{(*)},\tau}_{FB} \approx -0.359(0.064)$, and they can be enhanced (decreased) to be $\bar A^{D^{(*)},\tau}_{FB} \approx -0.33 (0.02)$.

  • The Neutrino Option. (arXiv:1703.10924v2 [hep-ph] UPDATED)

    Authors: llaria Brivio, Michael Trott

    The minimal seesaw scenario can radiatively generate the Higgs potential to induce electroweak symmetry breaking while supplying an origin of the Higgs vacuum expectation value from an underlying Majorana scale. If the Higgs potential and (derived) electroweak scale have this origin, the heavy $\rm SU(3) \times SU(2) \times U(1)_Y$ singlet states are expected to reside at $m_N \sim 10-500 \, {\rm PeV} $ for couplings $|\omega| \sim 10^{-4.5}-10^{-6}$ between the Majorana sector and the Standard Model. In this framework, the challenge of the electroweak scale hierarchy problem is replaced with a need to generate or accommodate PeV Majorana mass scales in ultraviolet models; the usual hierarchy problem is absent as the electroweak scale is not a fundamental scale.

  • A global view on the Higgs self-coupling. (arXiv:1704.01953v2 [hep-ph] UPDATED)

    Authors: Stefano Di Vita, Christophe Grojean, Giuliano Panico, Marc Riembau, Thibaud Vantalon

    The Higgs self-coupling is notoriously intangible at the LHC. It was recently proposed to probe the trilinear Higgs interaction through its radiative corrections to single-Higgs processes. This approach however requires to disentangle these effects from those associated to deviations of other Higgs-couplings to fermions and gauge bosons. We show that a global fit exploiting only single-Higgs inclusive data suffers from degeneracies that prevent one from extracting robust bounds on each individual coupling. We show how the inclusion of double-Higgs production via gluon fusion, and the use of differential measurements in the associated single-Higgs production channels WH, ZH and ttH, can help to overcome the deficiencies of a global Higgs-couplings fit. In particular, we bound the variations of the Higgs trilinear self-coupling relative to its SM value to the interval [0.1, 2.3] at 68% confidence level at the high-luminosity LHC, and we discuss the robustness of our results against various assumptions on the experimental uncertainties and the underlying new physics dynamics. We also study how to obtain a parametrically enhanced deviation of the Higgs self-couplings and we estimate how large this deviation can be in a self-consistent effective field theory framework.

  • Wilsonian Dark Matter in String Derived $Z^\prime$ Model. (arXiv:1704.02579v2 [hep-ph] UPDATED)

    Authors: L. Delle Rose, A.E. Faraggi, C. Marzo, J. Rizos

    The dark matter issue is among the most perplexing in contemporary physics. The problem is more enigmatic due to the wide range of possible solutions, ranging from the ultra-light to the super-massive. String theory gives rise to plausible dark matter candidates due to the breaking of the non--Abelian Grand Unified Theory (GUT) symmetries by Wilson lines. The physical spectrum then contains states that do not satisfy the quantisation conditions of the unbroken GUT symmetry. Given that the Standard Model states are identified with broken GUT representations, and provided that any ensuing symmetry breaking is induced by components of GUT states, leaves a remnant discrete symmetry that forbid the decay of the Wilsonian states. A class of such states are obtained in a heterotic-string derived $Z^\prime$ model. The model exploits the spinor-vector duality symmetry, observed in the fermionic $Z_2\times Z_2$ heterotic-string orbifolds, to generate a $Z^\prime\in E_6$ symmetry that may remain unbroken down to low energies. The $E_6$ symmetry is broken at the string level with discrete Wilson lines. The Wilsonian dark matter candidates in the string derived model are $SO(10)$, and hence Standard Model, singlets and possess non-$E_6$ $U(1)_{Z^\prime}$ charges. Depending on the $U(1)_{Z^\prime}$ breaking scale and the reheating temperature they give rise to different scenarios for the relic abundance, and in accordance with the cosmological constraints.

  • Axion-Like Particles and Recent Observations of the Cosmic Infrared Background Radiation. (arXiv:1704.05189v2 [hep-ph] UPDATED)

    Authors: Kazunori Kohri, Hideo Kodama

    The CIBER collaboration released their first observational data of the Cosmic IR background (CIB) radiation, which has significant excesses at around the wavelength $\sim$ 1 $\mu$m compared to theoretically-inferred values. The amount of the CIB radiation has a significant influence on the opaqueness of the Universe for TeV gamma-rays emitted from distant sources such as AGNs. With the value of CIB radiation reported by the CIBER experiment, through the reaction of such TeV gamma-rays with the CIB photons, the TeV gamma-rays should be significantly attenuated during propagation, which would lead to energy spectra in disagreement with current observations of TeV gamma ray sources. In this article, we discuss a possible resolution of this tension between the TeV gamma-ray observations and the CIB data in terms of axion [or Axion-Like Particles (ALPs)] that may increase the transparency of the Universe by the anomaly-induced photon-axion mixing. We find a region in the parameter space of the axion mass, $m_a \sim 7 \times 10^{-10} - 5 \times 10^{-8}$eV, and the axion-photon coupling constant, $1.2 \times 10^{-11} {\rm GeV}^{-1} \lesssim g_{a\gamma} \lesssim 8.8 \times 10^{-10} {\rm GeV}^{-1}$ that solves this problem.

  • Laminar and turbulent dynamos in chiral magnetohydrodynamics-I: Theory. (arXiv:1705.00378v3 [physics.plasm-ph] UPDATED)

    Authors: I. Rogachevskii, O. Ruchayskiy, A. Boyarsky, J. Fröhlich, N. Kleeorin, A. Brandenburg, J. Schober

    The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma (\emph{chiral magnetic effect}). We present a self-consistent treatment of the \emph{chiral MHD equations}, which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that the chiral magnetic effect decreases the frequency of the Alfv\'{e}n wave for incompressible flows, increases the frequencies of the Alfv\'{e}n wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark--gluon plasma.

  • Extracting dark matter signatures from atomic clock stability measurements. (arXiv:1705.05833v2 [hep-ph] UPDATED)

    Authors: Tigran Kalaydzhyan, Nan Yu

    We analyze possible effects of the dark matter environment on the atomic clock stability measurements. The dark matter is assumed to exist in a form of waves of ultralight scalar fields or in a form of topological defects (monopoles and strings). We identify dark matter signal signatures in clock Allan deviation plots that can be used to constrain the dark matter coupling to the Standard Model fields. The existing data on the Al+/Hg+ clock comparison are used to put new limits on the dilaton dark matter in the region of masses m > 10^{-15} eV. We also estimate the sensitivities of future atomic clock experiments in space, including the cesium microwave and strontium optical clocks aboard the International Space Station, as well as a potential nuclear clock. These experiments are expected to put new limits on the topological dark matter in the range of masses 10^{-10} eV < m < 10^{-6} eV.

  • The $H_0$ tension in light of vacuum dynamics in the Universe. (arXiv:1705.06723v4 [astro-ph.CO] UPDATED)

    Authors: Joan Sola, Adria Gomez-Valent, Javier de Cruz Perez

    Despite the outstanding achievements of modern cosmology, the classical dispute on the precise value of $H_0$, which is the first ever parameter of modern cosmology and one of the prime parameters in the field, still goes on and on after over half a century of measurements. Recently the dispute came to the spotlight with renewed strength owing to the significant tension (at $>3\sigma$ c.l.) between the latest Planck determination obtained from the CMB anisotropies and the local (distance ladder) measurement from the Hubble Space Telescope (HST), based on Cepheids. In this work, we investigate the impact of the running vacuum model (RVM) and related models on such a controversy. For the RVM, the vacuum energy density $\rho_{\Lambda}$ carries a mild dependence on the cosmic expansion rate, i.e. $\rho_{\Lambda}(H)$, which allows to ameliorate the fit quality to the overall $SNIa+BAO+H(z)+LSS+CMB$ cosmological observations as compared to the concordance $\Lambda$CDM model. By letting the RVM to deviate from the vacuum option, the equation of state $w=-1$ continues to be favored by the overall fit. Vacuum dynamics also predicts the following: i) the CMB range of values for $H_0$ is more favored than the local ones, and ii) smaller values for $\sigma_8(0)$. As a result, a better account for the LSS structure formation data is achieved as compared to the $\Lambda$CDM, which is based on a rigid (i.e. non-dynamical) $\Lambda$ term.

  • Pre-inflationary universe in loop quantum cosmology. (arXiv:1705.07544v3 [gr-qc] UPDATED)

    Authors: Tao Zhu, Anzhong Wang, Gerald Cleaver, Klaus Kirsten, Qin Sheng

    The evolutions of the flat FLRW universe and its linear perturbations are studied systematically in the dressed metric approach of LQC. When it is dominated by the kinetic energy of the inflaton at the quantum bounce, the evolution of the background can be divided into three different phases prior to the preheating, {\em bouncing, transition and slow-roll inflation}. During the bouncing phase, the evolution is independent of not only the initial conditions, but also the inflationary potentials. In particular, the expansion factor can be well described by the same exact solution in all the cases considered. In contrast, in the potential dominated case such a universality is lost. It is because of this universality that the linear perturbations are also independent of the inflationary models and obtained exactly. During the transition phase, the evolutions of the background and its linear perturbations are found explicitly, and then matched to the ones given in the other two phases. Hence, once the initial conditions are imposed, the linear scalar and tensor perturbations will be uniquely determined. Considering two different sets of initial conditions, one imposed during the contracting phase and the other at the bounce, we calculate the Bogoliubov coefficients and find that the two sets yield the same results and all lead to particle creations at the onset of the inflation. Due to the pre-inflationary dynamics, the scalar and tensor power spectra become scale-dependent. Comparing with the Planck 2015 data, we find constraints on the total e-folds that the universe must have expanded since the bounce, in order to be consistent with current observations.

  • Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments. (arXiv:1706.01505v3 [astro-ph.HE] UPDATED)

    Authors: Csaba Balázs, Jan Conrad, Ben Farmer, Thomas Jacques, Tong Li, Manuel Meyer, Farinaldo S. Queiroz, Miguel A. Sánchez-Conde

    Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential $\gamma$-ray signals from dark matter (DM) annihilation above $\sim50$ GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate $\gamma$-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC) and direct detection experiments. For DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.

  • CP violating anomalous couplings in $W$ jet production at the LHC. (arXiv:1708.04402v2 [hep-ph] UPDATED)

    Authors: Hai Tao Li, German Valencia

    T-odd correlations in $Wj$ production at the LHC have been studied recently as a way to measure a phase produced by QCD at NLO by Frederix et. al. That study found that the induced asymmetry could be observed with 20 fb$^{-1}$ of 8 TeV data. These T-odd asymmetries can also be induced by CP violating new physics interfering with the SM at LO. In this paper we study this possibility using effective Lagrangians to describe the new physics. We find that the leading contribution arises at dimension eight, and that it necessarily introduces flavor changing neutral currents as well. We discuss the constraints that can be placed on the flavor structure of the new physics operator from studies of FCNC in kaon and B meson decays and then compare the T-odd correlations in $Wj$ induced by CP violating new physics to those induced by QCD at NLO. We quantify the level at which these couplings can be probed at the LHC, and find that they will not affect a measurement of the NLO QCD phases.

  • Dependencies of Lepton Angular Distribution Coefficients on the Transverse Momentum and Rapidity of$Z$ Bosons Produced in $pp$ Collisions at LHC. (arXiv:1708.05807v2 [hep-ph] UPDATED)

    Authors: Wen-Chen Chang, Randall Evan McClellan, Jen-Chieh Peng, Oleg Teryaev

    High precision data of lepton angular distributions for $\gamma^*/Z$ production in $pp$ collisions at the LHC, covering broad ranges of dilepton transverse momenta ($q_T$) and rapidity ($y$), were recently reported. Strong $q_T$ dependencies were observed for several angular distribution coefficients, $A_i$, including $A_0 - A_4$. Significant $y$ dependencies were also found for the coefficients $A_1$, $A_3$ and $A_4$, while $A_0$ and $A_2$ exhibit very weak rapidity dependence. Using an intuitive geometric picture we show that the $q_T$ and $y$ dependencies of the angular distributions coefficients can be well described.

  • Dark Matter Results From 54-Ton-Day Exposure of PandaX-II Experiment. (arXiv:1708.06917v2 [astro-ph.CO] UPDATED)

    Authors: PandaX-II Collaboration: Xiangyi Cui, Abdusalam Abdukerim, Wei Chen, Xun Chen, Yunhua Chen, Binbin Dong, Deqing Fang, Changbo Fu, Karl Giboni, Franco Giuliani, Linhui Gu, Yikun Gu, Xuyuan Guo, Zhifan Guo, Ke Han, Changda He, Di Huang, Shengming He, Xingtao Huang, Zhou Huang, Xiangdong Ji, Yonglin Ju, Shaoli Li, Yao Li, Heng Lin, Huaxuan Liu, Jianglai Liu, Yugang Ma, Yajun Mao, Kaixiang Ni, Jinhua Ning, Xiangxiang Ren, Fang Shi, Andi Tan, Cheng Wang, Hongwei Wang, Meng Wang, Qiuhong Wang, Siguang Wang, Xiuli Wang, Xuming Wang, Qinyu Wu, Shiyong Wu, Mengjiao Xiao, Pengwei Xie, Binbin Yan, Yong Yang, Jianfeng Yue, Dan Zhang, Hongguang Zhang, Tao Zhang, Tianqi Zhang, Li Zhao, Jifang Zhou, Ning Zhou, Xiaopeng Zhou

    We report a new search of weakly interacting massive particles (WIMPs) using the combined low background data sets in 2016 and 2017 from the PandaX-II experiment in China. The latest data set contains a new exposure of 77.1 live day, with the background reduced to a level of 0.8$\times10^{-3}$ evt/kg/day, improved by a factor of 2.5 in comparison to the previous run in 2016. No excess events were found above the expected background. With a total exposure of 5.4$\times10^4$ kg day, the most stringent upper limit on spin-independent WIMP-nucleon cross section was set for a WIMP with mass larger than 100 GeV/c$^2$, with the lowest exclusion at 8.6$\times10^{-47}$ cm$^2$ at 40 GeV/c$^2$.

  • Particle temperature and the Chiral Vortical Effect in the early universe. (arXiv:1709.00211v2 [hep-ph] UPDATED)

    Authors: Tamal K. Mukherjee, Soma Sanyal

    We study the effect of hotter or colder particles on the evolution of the chiral magnetic field in the early universe. We are interested in the temperature dependent term in the chiral vortical effect. There are no changes in the magnetic energy spectrum at large lengthscales but in the Kolmogorov regime we do find a difference. Our numerical results show that the Gaussian peak in the magnetic spectrum becomes negatively skewed. The negatively skewed peak can be fitted with a beta distribution. Analytically one can relate the non-Gaussianity of the distribution to the temperature dependent vorticity term. The vorticity term is therefore responsible for the beta distribution in the magnetic spectrum. Since the beta distribution has already been used to model turbulent dispersion in fluids, hence it seems that the presence of hotter or colder particles may lead to turbulence in the magnetized plasma.

  • Mass generation by a Lorentz-invariant gas of spacetime defects. (arXiv:1703.10585v3 [hep-th] CROSS LISTED)

    Authors: F.R. Klinkhamer, J.M. Queiruga

    We present a simple model of defects embedded in flat spacetime, where the model is designed to maintain Lorentz invariance over large length scales. Even without remnant Lorentz violation, there are still effects from these spacetime defects on the propagation of physical fields, notably mass generation for scalars and Dirac fermions.

  • The Toric SO(10) F-Theory Landscape. (arXiv:1709.06609v1 [hep-th] CROSS LISTED)

    Authors: Wilfried Buchmuller, Markus Dierigl, Paul-Konstantin Oehlmann, Fabian Ruehle

    Supergravity theories in more than four dimensions with grand unified gauge symmetries are an important intermediate step towards the ultraviolet completion of the Standard Model in string theory. Using toric geometry, we classify and analyze six-dimensional F-theory vacua with gauge group SO(10) taking into account Mordell-Weil U(1) and discrete gauge factors. We determine the full matter spectrum of these models, including charged and neutral SO(10) singlets. Based solely on the geometry, we compute all matter multiplicities and confirm the cancellation of gauge and gravitational anomalies independent of the base space. Particular emphasis is put on symmetry enhancements at the loci of matter fields and to the frequent appearance of superconformal points. They are linked to non-toric K\"ahler deformations which contribute to the counting of degrees of freedom. We compute the anomaly coefficients for these theories as well by using a base-independent blow-up procedure and superconformal matter transitions. Finally, we identify six-dimensional supergravity models which can yield the Standard Model with high-scale supersymmetry by further compactification to four dimensions in an Abelian flux background.

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