Wed·Dec 30, 2015Wednesday·December 30, 2015

1. 01*

   Neutrino Catalyzed Diphoton Excess

   Wei Chao🇺🇸

   In this paper we explain the 750 GeV diphoton resonance observed at the run-2 LHC as a scalar singlet $S$, that plays a key rule in generating tiny but nonzero Majorana neutrino masses. The model contains four electroweak singlets: two leptoquarks, a singly charged scalar and a neutral scalar $S$. Majorana neutrino masses might be generated at the two-loop level as $S$ get nonzero vacuum expectation value. $S$ can be produced at the LHC through the gluon fusion and decays into diphoton at the one-loop level with charged scalars running in the loop. The model fits perfectly with a wide width of the resonance. Constraints on the model are investigated, which shows a negligible mixing between the resonance and the standard model Higgs boson.

   hep-phNPB(2016)·79 citations
2. 02*

   A Promising Interpretation of Diphoton Resonance at 750 GeV

   Xiao-Jun Bi🇨🇳 · Ran Ding🇨🇳 · Yizhou Fan🇨🇳 · Li Huang🇨🇳 · Chuang Li🇨🇳 · Tianjun Li🇨🇳 · Shabbar Raza🇨🇳 · Xiao-Chuan Wang🇨🇳 · Bin Zhu🇨🇳

   Recently, an excess of events in diphoton channel with invariant mass of about 750 GeV has been reported by the ATLAS and CMS Collaborations. Considering it as a tantalizing hint for new physics beyond the Standard Model (SM), we propose a simple extension of the SM with an additional doublet Higgs $H^{{}^{\prime }}$ and a singlet $s$. We consider the neutral component $H_0^{\prime }$ of $H^{\prime }$ as the 750 GeV resonance, and assume that $s$ is lighter than 2.6 GeV. In particular, $H_0^{\prime }$ can be produced at tree level via $q\bar{q}$ production, and decay into a pair of $s$ at tree level. And then $s$ can decay into a pair of collimated photons, which cannot be distinguished at the LHC. We show that the diphoton production cross section can be from 3 to 13 $\mathrm{fb}$, the decay width of $H_0^{\prime }$ can be from 30 to 60 GeV, and all the current experimental constraints including dijet constraint can be satisfied.

   hep-phPRD(2016)·81 citations
3. 03*

   Indirect Constraints on the Scalar Di-Photon Resonance at the LHC

   Florian Goertz🇨🇭 · Jernej F. Kamenik🇸🇮 · Andrey Katz🇨🇭 · Marco Nardecchia🇬🇧

   Motivated by the tantalizing excesses recently reported in the di-photon invariant mass spectrum at the LHC, we scrutinize some implications of scalar di-photon resonances in high energy proton-proton collisions. In particular, indications of a large width impose several challenges for model building. We show how calculability and unitarity considerations severely limit possible perturbative realizations of such a signal and propose a simple criterion that can be adapted to any renormalizable model. Furthermore, we discuss correlations between a di-photon excess and precision observables, including the anomalous magnetic and electric dipole moments of quarks and leptons, neutral meson oscillations and radiative flavor changing neutral current mediated decays of heavy leptons and hadrons. We find that existing searches and measurements significantly constrain the possibilities for a scalar resonance decaying into final states involving Standard Model fermions. We propose future search strategies which could elucidate some remaining currently unconstrained decay channels and discuss possible correlations between the di-photon excess and several recently reported flavor anomalies, showing that the latter can be addressed in a new incarnation of a gauged $U(1{)}^{\prime }$ model, with the di-photon resonance being the physical remnant of the $U(1{)}^{\prime }$-breaking field.

   hep-phhep-exJHEP(2016)·117 citations
4. 04*

   750 GeV diphotons from closed string states

   Luis A. Anchordoqui🇺🇸 · Ignatios Antoniadis🇫🇷 · Haim Goldberg🇺🇸 · Xing Huang🇹🇼 · Dieter Lust🇩🇪 · Tomasz R. Taylor🇺🇸

   We show that low-mass-scale string compactifications, with a generic D-brane configuration that realizes the standard model by open strings, can explain the relatively broad peak in the diphoton invariant mass spectrum at 750 GeV recently reported by the ATLAS and CMS collaborations. Under reasonable assumptions, we demonstrate that the excess could originate from a closed string (possibly axionic) excitation \varphi that has a coupling with gauge kinetic terms. We estimate the \varphi production rate from photon-photon fusion in elastic pp scattering, using the effective photon and narrow width approximations. For string scales above todays lower limit M_s \approx 7 TeV, we can accommodate the diphoton rate observed at Run II while maintaining consistency with Run I data.

   hep-phhep-thPLB(2016)·80 citations
5. 05*

   Quark Seesaw, Vectorlike Fermions and Diphoton Excess

   P. S. Bhupal Dev🇩🇪 · Rabindra N. Mohapatra🇺🇸 · Yongchao Zhang🇧🇪

   We present a possible interpretation of the recent diphoton excess reported by the $\sqrt{s}=13$ TeV LHC data in quark seesaw left-right models with vectorlike fermions proposed to solve the strong $CP$ problem without the axion. The gauge singlet real scalar field responsible for the mass of the vectorlike fermions has the right production cross section and diphoton branching ratio to be identifiable with the reported excess at around 750 GeV diphoton invariant mass. Various ways to test this hypothesis as more data accumulates at the LHC are proposed.

   hep-phhep-exJHEP(2016)·148 citations
6. 06*

   Two Higgs doublets to explain the excesses $pp\to \gamma \gamma (750\mathrm{GeV})$ and $h\to {\tau }^{\pm }{\mu }^{\mp }$

   N. Bizot🇫🇷 · S. Davidson🇫🇷 · M. Frigerio🇫🇷 · J.-L. Kneur🇫🇷

   The two Higgs doublet model emerges as a minimal scenario in which to address, at the same time, the $\gamma \gamma$ excess at 750 GeV and the lepton flavour violating decay into ${\tau }^{\pm }{\mu }^{\mp }$ of the 125 GeV Higgs boson. The price to pay is additional matter to enhance the $\gamma \gamma$ rate, and a peculiar pattern for the lepton Yukawa couplings. We add TeV scale vector-like fermions and find parameter space consistent with both excesses, as well as with Higgs and electroweak precision observables.

   hep-phJHEP(2016)·115 citations
7. 07*

   Novel nonperturbative approach for radiative ${\bar{B}}^0({\bar{B}}_s^0)\to J/\psi \gamma$ decays

   Li-Sheng Geng🇨🇳 · Eulogio Oset🇪🇸

   Radiative ${\bar{B}}^0({\bar{B}}_s^0)\to J/\psi \gamma$ decays provide an interesting case to test our understanding of (non)perturbative QCD and eventually to probe physics beyond the standard model. Recently, the LHCb Collaboration has reported an upper bound, updating the results of the BABAR Collaboration. Previous theoretical predictions based on QCD factorization or perturbative QCD have shown large variations due to different treatment of nonfactorizable contributions and meson-photon transitions. In this paper, we report on a novel approach to estimate the decay rates, which is based on a recently proposed model for $B$ decays and the vector meson dominance hypothesis, widely tested in the relevant energy regions. The predicted branching ratios are $\mathrm{Br}[{\bar{B}}^0\to J/\psi \gamma ]=\left(3.50\pm 0.34_{-0.63}^{+1.12}\right)\times 10^{-8}$ and $\mathrm{Br}[{\bar{B}}_s^0\to J/\psi \gamma ]=\left(7.20\pm 0.68_{-1.30}^{+2.31}\right)\times 10^{-7}$. The first uncertainty is systematic and the second is statistical, originating from the experimental ${\bar{B}}_s^0\to J/\psi \varphi$ branching ratio.

   hep-phPRD(2016)·6 citations
8. 08*

   On the computation of finite bottom-quark mass effects in Higgs boson production

   Romain Mueller🇨🇭 · Deniz Gizem Öztürk🇨🇭

   We present analytic results for the partonic cross-sections contributing to the top-bottom interference in Higgs production via gluon fusion at hadron colliders at NLO accuracy in QCD. We develop a method of expansion in small bottom-mass for master integrals and combine it with the usual infinite top-mass effective theory. Our method of expansion admits a simple algorithmic description and can be easily generalized to any small parameter. These results for the integrated cross-sections will be needed in the computation of the renormalization counter-terms entering the computation of finite bottom-quark mass effects at NNLO.

   hep-phJHEP(2016)·45 citations
9. 09*

   Phenomenological QCD equations of state for neutron stars

   Toru Kojo🇺🇸 · Philip D. Powell🇺🇸 · Yifan Song🇺🇸 · Gordon Baym🇺🇸

   We delineate the properties of QCD matter at baryon density n_B=1-10n_0 (n_0: nuclear saturation density), through the construction of neutron star equations of state that satisfy the neutron star mass-radius constraints as well as physical conditions on the speed of sound. The QCD matter is described in the 3-window modeling: at n_B < 2n_0 purely nuclear matter; at n_B > 5n_0 percolated quark matter; and at 2n_0 < n_B < 5n_0 matter intermediate between these two which are constructed by interpolation. Using a schematic quark model with effective interactions inspired from hadron and nuclear physics, we analyze the strength of interactions necessary to describe observed neutron star properties. Our finding is that the interactions should remain as strong as in the QCD vacuum, indicating that gluons at n_B =1-10 n_0 remain non-perturbative even after quark matter formation.

   hep-phastro-ph.HEnucl-exnucl-thNPA(2016)·24 citations
10. 10*

    Cross sections for inelastic meson-meson scattering via quark-antiquark annihilation

    Zhen-Yu Shen🇨🇳 · Xiao-Ming Xu🇨🇳 · H. J. Weber🇺🇸

    We study inelastic meson-meson scattering that is governed by quark-antiquark annihilation and creation involving a quark and an antiquark annihilating into a gluon, and subsequently the gluon creating another quark-antiquark pair. The resultant hadronic reactions include for I=1: pion + pion to rho + rho, kaon + antikaon to kaon* + antikaon*, kaon + antikaon* to kaon* + antikaon*, kaon* + antikaon to kaon* + antikaon*, as well as pion + pion to kaon + antikaon, pion + rho to kaon + antikaon*, pion + rho to kaon* + antikaon, and kaon + antikaon to rho + rho. In each reaction, one or two Feynman diagrams are involved in the Born approximation. We derive formulas for the unpolarized cross section, the transition amplitude, and the transition potential for quark-antiquark annihilation and creation. The unpolarized cross sections for the reactions are calculated at six temperatures, and prominent temperature dependence is found. It is due to differences among mesonic temperature dependence in hadronic matter.

    hep-phPRD(2016)·9 citations
11. 11*

    General Analysis of the Charged Higgs Sector of the $Y=0$ Triplet-Singlet Extension of the MSSM at the LHC

    Priyotosh Bandyopadhyay🇮🇹 · Claudio Coriano🇮🇹 · Antonio Costantini🇮🇹

    We investigate the extended Higgs sectors, specially the charged Higgs sector in a supersymmetric $Y=0$ $SU(2)$ triplet and a Standard Model (SM) gauge singlet extension of SM. We show that in this model the allowed data for the Higgs boson interaction eigenstates tend to group into separate blocks for $SU(2)$ triplet, doublet and singlet. The triplet sector has two degenerate paired states, each pair composed of a mostly-triplet charged Higgs and of a mostly-triplet scalar or pseudoscalar state. The mostly-doublet sector involves a Standard Model like Higgs of 125 GeV and extra mass-degenerate states, composed of a charged, a scalar and a pseudoscalar. The CP-odd component of the singlet scalar, after supersymmetry breaking, takes the role of a pseudo-Nambu-Goldstone mode in the $Z_3$ symmetric case, while the CP-even one becomes decoupled. In a second part of our study we investigate the different decay processes allowed to a charged Higgs boson of this model. Specifically, we search for general signatures of the TNMSSM in order to distinguish among Higgs fields belonging to $SU(2)$ doublet, triplet and singlet representations at the LHC. We also propose few golden plated final state modes carrying the distinctive signatures of this model which could be investigated in collider searches. We also show how in the decoupling limit of the triplet ($|{\lambda }_T|\simeq 0$) affects the decays as well as the production channels at the LHC.

    hep-phPRD(2016)·26 citations
12. 12*

    Top-quark Decays to Higgs boson in MSSM

    K.Suxho🇬🇷

    The decay of top-quark to light quarks and Higgs boson is an extremely rare process in the Standard Model (SM) framework. Any measurable signal for this process at the LHC is a smoking gun for new physics. In the framework of Minimal Supersymmetric Standard Model (MSSM) there is a possibility that the branching ratio for this process to reach values several orders of magnitude larger than the corresponding of SM. Having as a primary goal the search of Flavour Changing Neutral Currents (FCNC) processes that could be measurable at current or future LHC runing, we present a calculation in the framework of R-parity conserving MSSM for the decay of top quark to light quarks and the Higgs boson. Considering different constraints, and carefully looking at the cancellations that occur between different contributions, we deduce that there are two possible enhanced scenarios for this process: the first arises from the holomorphic SUSY breaking terms containing right handed up squark mass insertions and the second comes from the dominance of non-holomorphic SUSY breaking terms in combination with a light Higgs boson sector.

    hep-phPoS(2015)·4 citations
13. 13*

    Classically Scale Invariant Inflation and (A)gravity

    Arsham Farzinnia🇰🇷

    In this talk, I present the minimal classically scale-invariant and $CP$-symmetric extension of the standard model, containing one additional complex gauge singlet and three flavors of right-handed Majorana neutrinos, incorporated within a renormalizable framework of gravity, consistent with these symmetries; the Agravity. I particularly focus on the slow-roll inflationary paradigm within this framework, by identifying the pseudo-Nambu-Goldstone boson of the (approximate) scale symmetry with the inflaton field, constructing its one-loop effective potential, computing the slow-roll parameters and the inflationary observables, and demonstrating the compatibility of the small field inflation scenario with the latest Planck collaboration data sets.

    hep-phInt.J.Mod.Phys.Conf.Ser.(2016)·1 citation
14. 14*

    In-medium jet evolution: interplay between broadening and decoherence effects

    Liliana Apolinário🇵🇹 · Néstor Armesto🇪🇸 · Guilherme Milhano🇵🇹 · Carlos A. Salgado🇪🇸

    The description of the modifications of the coherence pattern in a parton shower, in the presence of a QGP, has been actively addressed in recent studies. Among the several achievements, finite energy corrections, transverse momentum broadening due to medium interactions and interference effects between successive emissions have been extensively improved as they seem to be essential features for a correct description of the results obtained in heavy-ion collisions. In this work, based on the insights of our previous work [1], we explore the physical interplay between broadening and decoherence, by generalising previous studies of medium-modifications of the antenna spectrum [2, 3, 4] - so far restricted to the case where transverse motion is neglected. The result allow us to identify two quantities controlling the decoherence of a medium modified shower that can be used as building blocks for a successful future generation of jet quenching Monte Carlo simulators: a generalisation of the ${\Delta }_{med}$ parameter of the works of [2, 4] - that controls the interplay between the transverse scale of the hard probe and the transverse resolution of the medium - and of the ${\Delta }_{coh}$ in [1] - that dictates the interferences between two emitters as a function of the transverse momentum broadening acquired by multiple scatterings with the medium.

    hep-phnucl-thNPA(2016)·3 citations
15. 15*

    Electroweak Symmetry Breaking and the Higgs Boson

    Antonio Pich🇪🇸

    The first LHC run has confirmed the Standard Model as the correct theory at the electroweak scale, and the existence of a Higgs-like particle associated with the spontaneous breaking of the electroweak gauge symmetry. These lectures overview the present knowledge on the Higgs boson and discuss alternative scenarios of electroweak symmetry breaking which are already being constrained by the experimental data.

    hep-phhep-exActa Phys.Polon.B(2016)·26 citations
16. 16*

    Modified gravity and dark matter

    Jose A. R. Cembranos🇪🇸

    The fundamental nature of Dark Matter (DM) has not been established. Indeed, beyond its gravitational effects, DM remains undetected by present experiments. In this situation, it is reasonable to wonder if other alternatives can effectively explain the observations usually associated with the existence of DM. The modification of the gravitational interaction has been studied in this context from many different approaches. However, the large amount of different astrophysical evidences makes difficult to think that modified gravity can account for all these observations. On the other hand, if such a modification introduces new degrees of freedom, they may work as DM candidates. We will summarize the phenomenology of these gravitational dark matter candidates by analyzing minimal models.

    hep-phastro-ph.COgr-qcJ.Phys.Conf.Ser.(2016)·24 citations
17. 17*

    Choked Jets and Low-Luminosity Gamma-Ray Bursts as Hidden Neutrino Sources

    Nicholas Senno🇺🇸 · Kohta Murase🇺🇸 · Peter Meszaros🇺🇸

    We consider gamma-ray burst (GRB) jets that are choked by extended material as sources of high-energy cosmic neutrinos. We take into account the jet propagation physics both inside the progenitor star and the surrounding dense medium. Radiation constraints, which are relevant for high-energy neutrino production are considered as well. Efficient shock acceleration of cosmic rays is possible for sufficiently low-power jets and/or jets buried in a dense, extended wind or outer envelope. Such conditions also favor GRB jets to become stalled, and the necessary conditions for stalling are explicitly derived. Such choked jets may explain transrelativistic supernovae (SNe) and low-luminosity (LL) GRBs, giving a unified picture of GRBs and GRB-SNe. Focusing on this unified scenario for GRBs, we calculate the resulting neutrino spectra from choked jets including the relevant microphysical processes such as multipion production in pp and pgamma interactions, as well as the energy losses of mesons and muons. We obtain diffuse neutrino spectra using the latest results for the luminosity function of LL GRBs. Although uncertainties are large, we confirm that LL GRBs can potentially give a significant contribution to the diffuse neutrino flux. Our results are consistent with the present IceCube data and do not violate the stacking limits on classical high-luminosity GRBs. We find that high-energy neutrino production in choked jets is dominated by pgamma interactions. These sources are dark in GeV-TeV gamma-rays, and do not contribute significantly to the Fermi diffuse gamma-ray background. Assuming stalled jets can launch a quasi-spherical shock in the dense medium, precursor TeV neutrinos emerging prior to the shock breakout gamma-ray emission can be used as smoking gun evidence for a choked jet model for LL GRBs. Our results strengthen the relevance of wide field-of-view sky monitors.

    ↳ astro-ph.HEhep-phPRD(2016)·219 citations
18. 18*

    Study of the Renormalization-Group Evolution of $\mathcal{N}=1$ Supersymmetric Gauge Theories Using Padé Approximants

    Gongjun Choi🇺🇸 · Robert Shrock🇺🇸

    We study asymptotically free SU($N_c$) gauge theories with $\mathcal{N}=1$ supersymmetry, including the purely gluonic theory and theories with $N_f$ copies of a pair of massless chiral superfields in the respective representations $R$ and $\bar{R}$ of SU($N_c$). The cases in which $R$ is the fundamental representation and the symmetric and antisymmetric rank-2 tensor representation are considered. We calculate Padé approximants to the beta functions for these theories in the $\overline{\mathrm{DR}}$ scheme up to four-loop order for the gluonic theory and up to three-loop order for the theories with matter superfields and compare results for IR zeros and poles with results from the NSVZ beta function. Our calculations provide a quantitative measure, for these theories, of how well finite-order perturbative results calculated in one scheme reproduce properties of a known beta function calculated in a different scheme.

    ↳ hep-thhep-phPRD(2016)·11 citations
19. 19*

    Dynamical AdS strings across horizons

    Takaaki Ishii🇺🇸 · Keiju Murata🇯🇵

    We examine the nonlinear classical dynamics of a fundamental string in anti-de Sitter spacetime. The string is dual to the flux tube between an external quark-antiquark pair in $\mathcal{N}=4$ super Yang-Mills theory. We perturb the string by shaking the endpoints and compute its time evolution numerically. We find that with sufficiently strong perturbations the string continues extending and plunges into the Poincaré horizon. In the evolution, effective horizons are also dynamically created on the string worldsheet. The quark and antiquark are thus causally disconnected, and the string transitions to two straight strings. The forces acting on the endpoints vanish with a power law whose slope depends on the perturbations. The condition for this transition to occur is that energy injection exceeds the static energy between the quark-antiquark pair.

    ↳ hep-thgr-qchep-phJHEP(2016)·9 citations
20. 20*

    New approaches in the analysis of Dark Matter direct detection data: scratching below the surface of the most general WIMP parameter space

    Stefano Scopel🇰🇷 · Kook-Hyun Yoon🇰🇷 · Jong-Hyun Yoon (Sogang U.)🇰🇷

    We show that compatibility between the DAMA modulation result (as well as less statistically significant excesses such as the CDMS Silicon effect and the excess claimed by CRESST) with constraints from other experiments can be achieved by extending the analysis of direct detection data beyond the standard elastic scattering of a WIMP off nuclei with a spin--dependent or a spin--independent cross section and with a velocity distribution as predicted by the Isothermal Sphere model. To do so we discuss several new approaches for the analysis of Dark Matter direct detection data, with the goal to remove or reduce its dependence on specific theoretical assumptions, and to extend its scope: the factorization approach of astrophysics uncertainties, the classification and study of WIMP-nucleon interactions within non--relativistic field theory, inelastic scattering and isovector-coupling cancellations including subdominant two-nucleon NLO effects. Typically, combining two or more of these ingredients can lead to conclusions which are very different to what usually claimed in the literature. This shows that we are only starting now to scratch the surface of the most general WIMP direct detection parameter space.

    ↳ astro-ph.COhep-ph5 citations
21. 21*

    $\rho$ and $K^{\ast }$ resonances on the lattice at nearly physical quark masses and $N_f=2$

    Gunnar S. Bali🇩🇪 · Sara Collins🇩🇪 · Antonio Cox🇩🇪 · Gordon Donald🇩🇪 · Meinulf Göckeler🇩🇪 · C. B. Lang🇦🇹 · Andreas Schäfer🇩🇪

    Working with a pion mass $m_{\pi }\approx 150$ MeV, we study $\pi \pi$ and $K\pi$ scattering using two flavours of non-perturbatively improved Wilson fermions at a lattice spacing $a\approx 0.071$ fm. Employing two lattice volumes with linear spatial extents of $N_s=48$ and $N_s=64$ points and moving frames, we extract the phase shifts for p-wave $\pi \pi$ and $K\pi$ scattering near the $\rho$ and $K^{\ast }$ resonances.Comparing our results to those of previous lattice studies, that used pion masses ranging from about 200 MeV up to 470 MeV, we find that the coupling $g_{\rho \pi \pi }$ appears to be remarkably constant as a function of $m_{\pi }$.

    ↳ hep-lathep-phPRD(2016)·123 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.