Fri·May 20, 2016Friday·May 20, 2016

1. 01*

   Forward $J/\psi$ production at high energy: centrality dependence and mean transverse momentum

   B. Ducloué🇫🇮 · T. Lappi🇫🇮 · H. Mäntysaari🇺🇸

   Forward rapidity $J/\psi$ meson production in proton-nucleus collisions can be an important constraint of descriptions of the small-$x$ nuclear wavefunction. In an earlier work we studied this process using a dipole cross section satisfying the Balitsky-Kovchegov equation, fit to HERA inclusive data and consistently extrapolated to the nuclear case using a standard Woods-Saxon distribution. In this paper we present further calculations of these cross sections, studying the mean transverse momentum of the meson and the dependence on collision centrality. We also extend the calculation to backward rapidities using nuclear parton distribution functions. We show that the parametrization is overall rather consistent with the available experimental data. However, there is a tendency towards a too strong centrality dependence. This can be traced back to the rather small transverse area occupied by small-$x$ gluons in the nucleon that is seen in the HERA data, compared to the total inelastic nucleon-nucleon cross section.

   hep-phnucl-thPRD(2016)·51 citations
2. 02*

   More Lepton Flavor Violating Observables for LHCb's Run 2

   Diego Guadagnoli🇫🇷 · Dmitri Melikhov🇷🇺 · Meril Reboud🇫🇷

   The R_K measurement by LHCb suggests non-standard lepton non-universality (LNU) to occur in b -> s l+ l- transitions, with effects in muons rather than electrons. A number of other measurements of b -> s l+ l- transitions by LHCb and B-factories display disagreement with the SM predictions and, remarkably, these discrepancies are consistent in magnitude and sign with the R_K effect. Non-standard LNU suggests non-standard lepton flavor violation (LFV) as well, for example in B -> K l l' and B_s -> l l'. There are good reasons to expect that the new effects may be larger for generations closer to the third one. In this case, the B_s -> mu e decay may be the most difficult to reach experimentally. We propose and study in detail the radiative counterpart of this decay, namely B_s -> mu e gamma, whereby the chiral-suppression factor is replaced by a factor of order alpha/pi. A measurement of this mode would be sensitive to the same physics as the purely leptonic LFV decay and, depending on experimental efficiencies, it may be more accessible. A realistic expectation is a factor of two improvement in statistics for either of the B_{d,s} modes.

   hep-phhep-exPLB(2016)·34 citations
3. 03*

   IceCube PeV Neutrinos and Leptophilic Dark Matter

   Marco Chianese🇮🇹

   We analyze the scenario where the IceCube high energy neutrino events are explained in terms of an extraterrestrial flux due to two different components: a contribution coming from know astrophysical sources for energies up to few hundreds TeV and a top-down contribution originated by the decay of heavy dark matter particles with a mass of few PeV. Contrary to previous approaches, we consider a leptophilic three-body decay that dominates at PeV energies due to the absence of quarks in the final state. We find that the theoretical predictions of such a scenario are in a slightly better agreement with the IceCube data if the astrophysical component has a cut-off at about 100 TeV. This interpretation of IceCube data can be easily tested in the near future since the decaying dark matter scenario predicts a sharp cut-off at PeV energy scale and the observation of an anisotropy towards Galactic Center of our Galaxy in contrast with the isotropic astrophysical flux.

   hep-phastro-ph.COastro-ph.HEJ.Phys.Conf.Ser.(2016)·6 citations
4. 04*

   CP-even scalar boson production via gluon fusion at the LHC

   Charalampos Anastasiou🇨🇭 · Claude Duhr🇨🇭 · Falko Dulat🇨🇭 · Elisabetta Furlan🇨🇭 · Thomas Gehrmann🇨🇭 · Franz Herzog🇳🇱 · Achilleas Lazopoulos🇨🇭 · Bernhard Mistlberger🇨🇭

   In view of the searches at the LHC for scalar particle resonances in addition to the 125 GeV Higgs boson, we present the cross section for a CP-even scalar produced via gluon fusion at N3LO in perturbative QCD assuming that it couples directly to gluons in an effective theory approach. We refine our prediction by taking into account the possibility that the scalar couples to the top-quark and computing the corresponding contributions through NLO in perturbative QCD. We assess the theoretical uncertainties of the cross section due to missing higher-order QCD effects and we provide the necessary information for obtaining the cross section value and uncertainty from our results in specific scenarios beyond the Standard Model. We also give detailed results for the case of a 750 GeV scalar, which will be the subject of intense experimental studies.

   hep-phhep-exJHEP(2016)·33 citations
5. 05*

   Double vector meson production in photon - hadron interactions at hadronic colliders

   V.P. Goncalves🇧🇷 · B.D. Moreira🇧🇷 · F.S. Navarra🇧🇷

   In this paper we analyse the double vector meson production in photon -- hadron ($\gamma h$) interactions at $pp/pA/AA$ collisions and present predictions for the $\rho \rho$, $J/\Psi J/\Psi$ and $\rho J/\Psi$ production considering the double scattering mechanism. We estimate the total cross sections and rapidity distributions at LHC energies and compare our results with the predictions for the double vector meson production in $\gamma \gamma$ interactions at hadronic colliders. We present predictions for the different rapidity ranges probed by the ALICE, ATLAS, CMS and LHCb Collaborations. Our results demonstrate that the $\rho \rho$ and $J/\Psi J/\Psi$ production in $PbPb$ collisions is dominated by the double scattering mechanism, while the two - photon mechanism dominates in $pp$ collisions. Moreover, our results indicate that the analysis of the $\rho J/\Psi$ production at LHC can be useful to constrain the double scattering mechanism.

   hep-phhep-exnucl-exnucl-thEPJC(2016)·26 citations
6. 06*

   Summing threshold logs in a parton shower

   Zoltan Nagy🇩🇪 · Davison E. Soper🇺🇸

   When parton distributions are falling steeply as the momentum fractions of the partons increases, there are effects that occur at each order in ${\alpha }_s$ that combine to affect hard scattering cross sections and need to be summed. We show how to accomplish this in a leading approximation in the context of a parton shower Monte Carlo event generator.

   hep-phJHEP(2016)·26 citations
7. 07*

   Prompt-photon plus jet photoproduction with ZEUS at DESY HERA in the parton Reggeization approach

   B.A. Kniehl🇩🇪 · M.A. Nefedov🇷🇺 · V.A. Saleev🇷🇺

   We study the photoproduction of isolated prompt photons associated with hadron jets in the framework of the parton Reggeization approach. The main improvements with respect to previous studies in the k_T-factorization framework include the application of the Reggeized-quark formalism, the generation of exactly gauge-invariant amplitudes with off-shell initial-state quarks, and the exact treatment of the gamma+R -> gamma+g box contribution with off-shell initial-state gluons. In this proceedings, the new data set, published recently by ZEUS collaboration is analyzed, were the distributions in photon and jet rapidity, transverse energy, azimuthal angle between photon and jet and proton momentum fraction are presented for different values of measured photon momentum fraction x_gamma <0.7, 0.8 and x_gamma>0.8$. The good agreement of measured distributions with our predictions is observed for the direct-dominating part of the data set. The comparison with the previous calculations in k_T-factorization, role of nonfactorizable higher-order and hadronization corrections is discussed.

   hep-phNucl.Part.Phys.Proc.(2016)·0 citations
8. 08*

   Exclusive $J/\psi$ Production in Diffractive Process with AdS/QCD Holographic Wave Function in BLFQ

   Ya-ping Xie · Xurong Chen

   The AdS/QCD holographic wave function of basis light-front quantization (BLFQ) for vector meson $J/\psi$ is applied in this manuscript. The exclusive production of $J/\psi$ in diffractive process is computed in dipole model with AdS/QCD holographic wave function. We use IP-Sat and IIM model in the calculation of the differential cross section of the dipole scattering off the proton. The prediction of AdS/QCD holographic wave function in BLFQ gives a good agreement to the experimental data.

   hep-ph0 citations
9. 09*

   Comment on "Dark Matter with Pseudoscalar-Mediated Interactions Explains the DAMA Signal and the Galactic Center Excess"

   Kwei-Chou Yang🇹🇼

   Arina et al. have proposed the Dirac fermionic dark matter with pseudoscalar-mediated interactions to explain the Galactic Center excess, correct relic density and DAMA signal. They have assumed that contact interactions remain roughly valid in calculating scattering rates at the direct detection even when the mediator mass is the same order as the typical momentum transfer. We show that such a replacement is not suitable. Adopting the full form of interactions, we show that the gamma-ray excess allowed parameters are completely outside of the DAMA iodine 3$\sigma$ region, even for heavy-flavor-universal couplings, for which $m_{DM}\sim 40$ GeV in the gamma-ray excess fit. As for Higgs-like couplings, the two regions overlap for $m_a\lesssim$ 15 MeV, where long-range interactions, instead of contact interactions, occur at the DAMA.

   hep-phastro-ph.COastro-ph.HE1 citation
10. 10*

    Light charged Higgs boson scenario in 3-Higgs doublet models

    A. G. Akeroyd🇬🇧 · Stefano Moretti🇬🇧 · Kei Yagyu🇬🇧 · Emine Yildirim🇬🇧

    The constraints from the measurements of the $B\to X_s\gamma$ decay rate on the parameter space of 3-Higgs Doublet Models (3HDMs), where all the doublets have non-zero vacuum expectation values, are studied at the next-to-leading order in QCD. In order to naturally avoid the presence of flavour changing neutral currents at the tree level, we impose two softly-broken discrete $Z_2$ symmetries. This gives rise to five independent types of 3HDMs that differ in their Yukawa couplings. We show that in all these 3HDMs (including the case of type-II-like Yukawa interactions) both masses of the two charged Higgs bosons $m_{H_1^{\pm }}$ and $m_{H_2^{\pm }}$ can be smaller than the top mass $m_t$ while complying with the constraints from $B\to X_s\gamma$. As an interesting phenomenological consequence, the branching ratios of the charged Higgs bosons decay into the $cb$ final states can be as large as $80\%$ when their masses are taken to be below $m_t$ in two of the five 3HDMs (named as Type-Y and Type-Z). This light charged Higgs boson scenario provides a hallmark 3HDM signature that cannot be realised in $Z_2$ symmetric 2-Higgs doublet models. We find that in the Type-Y and Type-Z 3HDMs the scenario with $90\mathrm{GeV}<m_{H_1^{\pm }}^{},m_{H_2^{\pm }}^{}<m_t$ is ruled out by the direct searches at the LHC, but in the Type-Y 3HDM $80\text{GeV}<m_{H_1^{\pm }}^{}<90\text{GeV}$ and $90\text{GeV}<m_{H_2^{\pm }}^{}<m_t$ is allowed by $B\to X_s\gamma$ and direct searches at LEP2, Tevatron and LHC due to the reduced sensitivity of these searches to the degenerate case $m_{H_1^{\pm }}\approx m_{W^{\pm }}$. The cases where only one or both charged Higgs bosons are above the top quark mass are also naturally allowed in the both Type-Y and Type-Z 3HDMs.

    hep-phInt.J.Mod.Phys.A(2017)·50 citations
11. 11*

    Is it $SU(2{)}_{\mathrm{L}}$ or just $U(1{)}_{\mathrm{Y}}$? $750$ GeV di-photon probes of the electroweak nature of new states

    Jose Miguel No🇬🇧

    The existence of a 750 GeV di-photon spin-0 resonance $S$ would imply the additional presence of new particles beyond the Standard Model, coupling directly to $S$ and electromagnetically charged. For an $SU(2{)}_{\mathrm{L}}$ singlet $S$, we explore the possibility of probing the $SU(2{)}_{\mathrm{L}}$ and $U(1{)}_{\mathrm{Y}}$ quantum numbers of the new states at the LHC by measuring/constraining the $WW$, $Z\gamma$ and $ZZ$ decays of $S$. We obtain robust prospects on the required LHC integrated luminosity to discover the new decay modes of $S$, and discuss the implications of these measurements for probing the electroweak nature of the new states. We also discuss the impact of $S$ mixing with the SM Higgs in such probes.

    hep-phPRD(2016)·6 citations
12. 12*

    E6Tensors: A Mathematica Package for E6 Tensors

    Thomas Deppisch🇩🇪

    We present the Mathematica package E6Tensors, a tool for explicit tensor calculations in E6 gauge theories. In addition to matrix expressions for the group generators of E6, it provides structure constants, various higher rank tensors and expressions for the representations 27, 78, 351 and 351'. This paper comes along with a short manual including physically relevant examples. I further give a complete list of gauge invariant, renormalisable terms for superpotentials and Lagrangians.

    hep-phhep-thComput.Phys.Commun.(2017)·12 citations
13. 13*

    Multiquark Hadrons - A New Facet of QCD

    Ahmed Ali🇩🇪

    I review some selected aspects of the phenomenology of multiquark states discovered in high energy experiments. They have four valence quarks (called tetraquarks) and two of them are found to have five valence quarks (called pentaquarks), extending the conventional hadron spectrum which consists of quark-antiquark $(q\bar{q})$ mesons and $qqq$ baryons. Multiquark states represent a new facet of QCD and their dynamics is both challenging and currently poorly understood. I discuss various approaches put forward to accommodate them, with emphasis on the diquark model.

    hep-phhep-exhep-lat12 citations
14. 14*

    Non-zero ${\theta }_{13}$ and leptonic CP phase with $A_4$ Symmetry

    Sruthilaya M.🇮🇳 · R. Mohanta🇮🇳

    We consider a model based on $A_4$ symmetry to explain the phenomenon of neutrino mixing. The spontaneous symmetry breaking of $A_4$ symmetry leads to a co-bimaximal mixing matrix at leading order. We consider the effect of higher order corrections in neutrino sector and find that the mixing angles thus obtained, come well within the $3\sigma$ ranges of their experimental values. We study the implications of this formalism on the other phenomenological observables, such as CP violating phase, Jarlskog invariant and the effective Majorana mass $|M_{ee}|$. We also obtain the branching ratio of the lepton flavour violating decay $\mu \to e\gamma$ in the context of this model and find that it can be less than its present experimental upper bound.

    hep-phEPJC(2017)·0 citations
15. 15*

    The b --> s l^+ l^- anomalies and their implications for new physics

    Sébastien Descotes-Genon🇫🇷 · Lars Hofer🇪🇸 · Joaquim Matias🇪🇸 · Javier Virto🇩🇪

    Recently, the LHC has found several anomalies in exclusive semileptonic b --> s l^+ l^- decays. In this proceeding, we summarize the most important results of our global analysis of the relevant decay modes. After a discussion of the hadronic uncertainties entering the theoretical predictions, we present an interpretation of the data in terms of generic new physics scenarios. To this end, we have performed model-independent fits of the corresponding Wilson coefficients to the data and have found that in certain scenarios the best fit point is prefererred over the Standard Model by a global significance of more than 4{\sigma}. Based on the results, the discrimination between high-scale new physics and low-energy QCD effects as well as the possibility of lepton-flavour universality violation are discussed.

    hep-ph10 citations
16. 16*

    Momentum transport in strongly coupled anisotropic plasmas in the presence of strong magnetic fields

    Stefano Ivo Finazzo (Sao Paulo, IFT)🇧🇷 · Renato Critelli (Sao Paulo U.)🇧🇷 · Romulo Rougemont (Sao Paulo U.)🇧🇷 · Jorge Noronha (Sao Paulo U.)🇧🇷

    We present a holographic perspective on momentum transport in strongly coupled, anisotropic non-Abelian plasmas in the presence of strong magnetic fields. We compute the anisotropic heavy quark drag forces and Langevin diffusion coefficients and also the anisotropic shear viscosities for two different holographic models, namely, a top-down deformation of strongly coupled $\mathcal{N}=4$ Super-Yang-Mills (SYM) theory triggered by an external Abelian magnetic field, and a bottom-up Einstein-Maxwell-dilaton (EMD) model which is able to provide a quantitative description of lattice QCD thermodynamics with $(2+1)$-flavors at both zero and nonzero magnetic fields. We find that, in general, energy loss and momentum diffusion through strongly coupled anisotropic plasmas are enhanced by a magnetic field being larger in transverse directions than in the direction parallel to the magnetic field. Moreover, the anisotropic shear viscosity coefficient is smaller in the direction of the magnetic field than in the plane perpendicular to the field, which indicates that strongly coupled anisotropic plasmas become closer to the perfect fluid limit along the magnetic field. We also present, in the context of the EMD model, holographic predictions for the entropy density and the crossover critical temperature in a wider region of the $(T,B)$ phase diagram that has not yet been covered by lattice simulations. Our results for the transport coefficients in the phenomenologically realistic magnetic EMD model could be readily used as inputs in numerical codes for magnetohydrodynamics.

    hep-phhep-lathep-thnucl-thPRD(2016)·164 citations
17. 17*

    Neutrino Oscillations With Two Sterile Neutrinos

    Leonard S. Kisslinger🇺🇸

    This work estimates the probability of $\mu$ to $e$ neutrino oscillation with two sterile neutrinos using a 5x5 U-matrix, an extension of the previous estimate with one sterile neutrino and a 4x4 U-matrix. The sterile neutrino-active neutrino mass differences and the mixing angles of the two sterile neutrinos with the three active neutrinos are taken from recent publications, and the oscillation probability for one sterile neutrino is compared to the previous estimate.

    hep-phInt.J.Theor.Phys.(2016)·0 citations
18. 18*

    Dimensional regularization is generic

    Kazuo Fujikawa🇯🇵

    The absence of the quadratic divergence in the Higgs sector of the Standard Model in the dimensional regularization is usually regarded to be an exceptional property of a specific regularization. To understand what is going on in the dimensional regularization, we illustrate how to reproduce the results of the dimensional regularization for the $\lambda {\varphi }^4$ theory in the more conventional regularization such as the higher derivative regularization; the basic postulate involved is that the quadratically divergent induced mass, which is independent of the scale change of the physical mass, is kinematical and unphysical. This is consistent with the derivation of the Callan-Symanzik equation, which is a comparison of two theories with slightly different masses, for the $\lambda {\varphi }^4$ theory without encountering the quadratic divergence. We thus suggest that the dimensional regularization is generic in a bottom-up approach starting with a successful low-energy theory. We also define a modified version of the mass independent renormalization for a scalar field which leads to the homogeneous renormalization group equation. Implications of the present analysis on the Standard Model at high energies and the presence or absence of SUSY at LHC energies are briefly discussed.

    ↳ hep-thhep-phInt.J.Mod.Phys.A(2016)·7 citations
19. 19*

    Test of the Einstein equivalence principle with spectral distortions in the cosmic microwave background

    Shun Arai🇯🇵 · Daisuke Nitta🇯🇵 · Hiroyuki Tashiro🇯🇵

    The Einstein Equivalence Principle~(EEP) can be verified by the measurement of the spectral distortions of the Cosmic Microwave Background (CMB). The existence of energy-dependency in the cosmological redshift effect means the EEP violation. Introducing the energy-dependent Friedmann-Robertson-Walker metric motivated by rainbow gravity, we show that the energy-dependent redshift effect causes the CMB spectral distortions. Assuming the simple energy-dependent form of the metric, we evaluate the distortions. From the COBE/FIRAS bound, we find that the deviation degree from the EEP, which is comparable to the difference of the parameterized-post-Newtonian parameter "gamma" in energy, is less than 10^{-9} at the CMB energy scale.

    ↳ astro-ph.COgr-qchep-phPRD(2016)·3 citations
20. 20*

    A particle-like description of Planckian black holes

    Euro Spallucci🇮🇹 · Anais Smailagic🇮🇹

    In this paper we abandon the idea that even a "quantum" black hole, of Planck size, can still be described as a classical, more or less complicated, geometry. Rather, we consider a genuine quantum mechanical approach where a Planckian black hole is, by all means, just another "particle", even if with a distinguishing property: its linear size increases with the energy. The horizon dynamics is equivalently described in terms of a particle moving in gravitational potential derived from the horizon equation itself in a self-consistent manner. The particle turning-points match the radius of the inner and outer horizons of a charged black hole. This classical model pave the way towards the wave equation for a truly quantum black hole. We compute the exact form of the wave function and determine the energy spectrum. Finally, we describe the classical limit in which the quantum picture correctly approaches the classical geometric formulation. We find that the quantum-to-classical transition occurs far above the Planck scale.

    ↳ hep-thgr-qchep-phquant-ph"Quantum Gravity: Theory and Research", E…·11 citations
21. 21*

    Spatially Assisted Schwinger Mechanism and Magnetic Catalysis

    Patrick Copinger🇯🇵 · Kenji Fukushima🇯🇵

    Using the worldline formalism we compute an effective action for fermions under a temporally modulated electric field and a spatially modulated magnetic field. It is known that the former leads to an enhanced Schwinger Mechanism, while we find that the latter can also result in enhanced particle production and even cause a reorganization of the vacuum to acquire a larger dynamical mass in equilibrium which spatially assists the Magnetic Catalysis.

    ↳ hep-thhep-phPRL(2016)·19 citations
22. 22*

    WarmAndFuzzy: the halo model beyond CDM

    David J. E. Marsh🇬🇧

    Cold dark matter (CDM) is a well established paradigm to describe cosmological structure formation, and works extraordinarily well on large, linear, scales. Progressing further in dark matter physics requires being able to understand structure formation in the non-linear regime, both for CDM and its alternatives. This short note describes a calculation, and accompanying code, WarmAndFuzzy, incorporating the popular models of warm and fuzzy dark matter (WDM and FDM) into the standard halo model to compute the non-linear matter power spectrum. The FDM halo model power spectrum has not been computed before. The FDM implementation models ultralight axions and other scalar fields with $m_a\approx 10^{-22}\text{ eV}$. The WDM implementation models thermal WDM with mass $m_X\approx 1\text{ keV}$. The halo model shows that differences between WDM, FDM, and CDM survive at low redshifts in the quasi-linear and fully non-linear regimes. The code uses analytic transfer functions for the linear power spectrum, modified collapse barriers in the halo mass function, and a modified concentration-mass relationship for the halo density profiles. Modified halo density profiles (for example, cores) are not included, but are under development. Cores are expected to have very minor effects on the power spectrum on observable scales. Applications of this code to the Lyman-$\alpha$ forest flux power spectrum and the cosmic microwave background lensing power spectrum will be discussed in companion papers. \textsc{WarmAndFuzzy} is available online at \url{https://github.com/DoddyPhysics/HMcode}, where collaboration in development is welcomed.

    ↳ astro-ph.COastro-ph.GAastro-ph.IMhep-ph53 citations
23. 23*

    Moriond Electroweak and Unified Theories 2016 - Experimental Summary

    Andreas Hoecker🇨🇭

    Summary of the experimental results presented at the 51st edition of the Moriond Electroweak and Unified Theories conference held in March 2016 at La Thuile, Italy.

    ↳ hep-exhep-ph3 citations
24. 24*

    Thermodynamics of Van der Waals Fluids with quantum statistics

    Krzysztof Redlich (Wroclaw U. & Darmstadt, EMMI & Duke U.)🇵🇱 · Kacper Zalewski (Cracow, INP & Jagiellonian U.)🇵🇱

    We consider thermodynamics of the van der Waals fluid of quantum systems. We derive general relations of thermodynamic functions and parameters of any ideal gas and the corresponding van der Waals fluid. This provides unambiguous generalization of the classical van der Waals theory to quantum statistical systems. As an example, we apply the van der Waals fluid with fermi statistics to characterize the liquid-gas critical point in nuclear matter. We also introduce the Bose-Einstein condensation in the relativistic van der Waals boson gas, and argue, that it exhibits two-phase structure separated in space.

    ↳ cond-mat.quant-gascond-mat.stat-mechhep-phActa Phys.Polon.B(2016)·34 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.