Wed·Nov 11, 2015Wednesday·November 11, 2015

1. 01*

   CP asymmetry in heavy Majorana neutrino decays at finite temperature: the nearly degenerate case

   Simone Biondini🇩🇪 · Nora Brambilla🇩🇪 · Miguel Angel Escobedo🇫🇷 · Antonio Vairo🇩🇪

   In a model where Majorana neutrinos heavier than the electroweak scale couple to Standard Model Higgs bosons and leptons, we compute systematically thermal corrections to the direct and indirect CP asymmetries in the Majorana neutrino decays. These are key ingredients entering the equations that describe the thermodynamic evolution of the induced lepton-number asymmetry eventually leading to the baryon asymmetry in the universe. We compute the thermal corrections in an effective field theory framework that assumes the temperature smaller than the masses of the Majorana neutrinos and larger than the electroweak scale, and we provide the leading corrections in an expansion of the temperature over the mass. In this work, we consider the case of two Majorana neutrinos with nearly degenerate masses.

   hep-phJHEP(2016)·22 citations
2. 02*

   Magnetic dipole moments for composite dark matter

   Alfredo Aranda🇲🇽 · Luis Barajas🇲🇽 · Jose A.R. Cembranos🇪🇸

   We study neutral dark matter candidates with a nonzero magnetic dipole moment. We assume that they are composite states of new fermions related to the strong phase of a new gauge interaction. In particular, invoking a dark flavor symmetry, we analyze the composition structure of viable candidates depending on the assignations of hypercharge and the multiplets associated to the fundamental constituents of the extended sector. We determine the magnetic dipole moments for the neutral composite states in terms of their constituents masses.

   hep-phastro-ph.COJCAP(2016)·8 citations
3. 03*

   Sensitivity to oscillation with a sterile fourth generation neutrino from ultra-low threshold neutrino-nucleus coherent scattering

   Bhaskar Dutta · Yu Gao · Andrew Kubik · Rupak Mahapatra · Nader Mirabolfathi · Louis E. Strigari · Joel W. Walker

   We discuss prospects for probing short-range sterile neutrino oscillation using neutrino-nucleus coherent scattering with ultra-low energy ($\sim 10$ eV - 100 eV) recoil threshold cryogenic Ge detectors. The analysis is performed in the context of a specific and contemporary reactor-based experimental proposal, developed in cooperation with the Nuclear Science Center at Texas A\&M University, and references developing technology based upon economical and scalable detector arrays. The baseline of the experiment is substantially shorter than existing measurements, as near as about 2 meters from the reactor core, and is moreover variable, extending continuously up to a range of about 10 meters. This proximity and variety combine to provide extraordinary sensitivity to a wide spectrum of oscillation scales, while facilitating the tidy cancellation of leading systematic uncertainties in the reactor source and environment. With 100~eV sensitivity, for exposures on the order of 200 kg$\cdot$y, we project an estimated sensitivity to first/fourth neutrino oscillation with a mass gap $\Delta m^2\sim 1{\mathrm{eV}}^2$ at an amplitude ${\sin }^{2}2\theta \sim 10^{-1}$, or $\Delta m^2\sim 0.2{\mathrm{eV}}^2$ at unit amplitude. Larger exposures, around 5,000 kg$\cdot$y, together with 10 eV sensitivity are capable of probing more than an additional order of magnitude in amplitude.

   hep-phhep-exnucl-exnucl-thPRD(2016)·71 citations
4. 04*

   Relaxion Cosmology and the Price of Fine-Tuning

   Stefano Di Chiara🇪🇪 · Kristjan Kannike🇪🇪 · Luca Marzola🇪🇪 · Antonio Racioppi🇪🇪 · Martti Raidal🇪🇪 · Christian Spethmann🇪🇪

   The relaxion scenario presents an intriguing extension of the standard model in which the particle introduced to solve to the strong CP problem, the axion, also achieves the dynamical relaxation of the Higgs boson mass term. In this work we complete this framework by proposing a scenario of inflationary cosmology that is consistent with all the observational constraints: the relaxion hybrid inflation with an asymmetric waterfall. In our scheme, the vacuum energy of the inflaton drives inflation in a natural way while the relaxion slow-rolls. The constraints on the present inflationary observables are then matched through a subsequent inflationary epoch driven by the inflaton. We quantify the amount of fine-tuning of the proposed inflation scenario, concluding that the inflaton sector severely decreases the naturalness of the theory.

   hep-phPRD(2016)·38 citations
5. 05*

   The MOMENT to search for CP violation

   Mattias Blennow🇸🇪 · Pilar Coloma🇺🇸 · Enrique Fernandez-Martinez🇪🇸

   In this letter, we analyze for the first time the physics reach in terms of sensitivity to leptonic CP violation of the proposed MuOn-decay MEdium baseline NeuTrino beam (MOMENT) experiment, a novel neutrino oscillation facility that would operate with neutrinos from muon decay. Apart from obtaining a sufficiently intense flux, the bottlenecks to the physics reach of this experiment will be achieving a high enough suppression of the atmospheric background and, particularly, attaining a sufficient level of charge identification. We thus present our results as a function of these two factors. As for the detector, we consider a very massive Gd-doped Water Cherenkov detector. We find that MOMENT will be competitive with other currently planned future oscillation experiments if a charge identification of at least 80 % can be achieved at the same time that the atmospheric background can be suppressed by at least a factor of ten. We also find a large synergy of MOMENT with the current generation of neutrino oscillation experiments, T2K and NOvA, which significantly enhances its final sensitivity.

   hep-phhep-exJHEP(2016)·19 citations
6. 06*

   Correlated Signals at the Energy and Intensity Frontiers from Nonabelian Kinetic Mixing

   G. Barello🇺🇸 · Spencer Chang🇺🇸 · Christopher A. Newby🇬🇧

   We show that when a dark abelian gauge sector and SU$(2{)}_L$ kinetically mix it necessarily generates a relation between the kinetic mixing strength and the mass of the mediating particle. Remarkably, this correspondence maps the weak scale directly to the kinetic mixing strengths being probed by modern fixed-target experiments and next generation flavor factories. This illuminates the exciting possibility of correlated discoveries of a new particle at the LHC and a dark photon at intensity frontier experiments. To motivate the scenario, we construct a simple model and explore its phenomenology and constraints.

   hep-phhep-exPRD(2016)·22 citations
7. 07*

   The QCD axion, precisely

   Giovanni Grilli di Cortona🇮🇹 · Edward Hardy🇮🇹 · Javier Pardo Vega🇮🇹 · Giovanni Villadoro🇮🇹

   We show how several properties of the QCD axion can be extracted at high precision using only first principle QCD computations. By combining NLO results obtained in chiral perturbation theory with recent Lattice QCD results the full axion potential, its mass and the coupling to photons can be reconstructed with percent precision. Axion couplings to nucleons can also be derived reliably, with uncertainties smaller than ten percent. The approach presented here allows the precision to be further improved as uncertainties on the light quark masses and the effective theory couplings are reduced. We also compute the finite temperature dependence of the axion potential and its mass up to the crossover region. For higher temperature we point out the unreliability of the conventional instanton approach and study its impact on the computation of the axion relic abundance.

   hep-phhep-exhep-latJHEP(2016)·1013 citations
8. 08*

   Neutrino dark energy and leptogenesis with TeV scale triplets

   Chandan Hati🇮🇳 · Utpal Sarkar🇮🇳

   We propose a realization of mass varying neutrino dark energy in two extensions of the Standard Model (SM) with a dynamical neutrino mass related to the acceleron field while satisfying the naturalness. In the first scenario the SM is extended to include a TeV scale scalar Higgs triplet ($\xi$) and a TeV scale second Higgs doublet ($\eta$), while in the second scenario an extension of the SM with fermion triplet $(\Sigma )$ is considered. We also point out the possible leptogenesis mechanisms for simultaneously generating the observed baryon asymmetry of the universe in both the scenarios and discuss the collider signatures for the TeV scale new fields which make these models testable in the current run of LHC.

   hep-phastro-ph.COEPJC(2016)·7 citations
9. 09*

   One-loop contributions to neutral minima in the inert doublet model

   P.M. Ferreira🇵🇹 · Bogumila Swiezewska🇵🇱

   The vacuum structure of the inert doublet model is analysed at the one-loop level using the effective potential formalism, to verify the validity of tree-level predictions for the properties of the global minimum. An inert minimum (with massive fermions) and an inert-like minimum (with massless fermions) can coexist at tree level. But the one-loop analysis reveals that the allowed parameter space for the coexistence of more than one minimum is larger than the tree-level expected one. It is also shown that for some choices of parameters, the global minimum found at the one-loop level may be inert (or inert-like), contrary to what the tree-level analysis indicates.

   hep-phJHEP(2016)·47 citations
10. 10*

    Jet-vetoed Higgs cross section in gluon fusion at N3LO+NNLL with small-R resummation

    Andrea Banfi🇬🇧 · Fabrizio Caola🇨🇭 · Frédéric A. Dreyer🇨🇭 · Pier F. Monni🇬🇧 · Gavin P. Salam🇨🇭 · Giulia Zanderighi🇨🇭 · Falko Dulat🇨🇭

    We present new results for the jet-veto efficiency and zero-jet cross section in Higgs production through gluon fusion. We incorporate the N${}^3$LO corrections to the total cross section, the NNLO corrections to the 1-jet rate, NNLL resummation for the jet $p_t$ and LL resummation for the jet radius dependence. Our results include known finite-mass corrections and are obtained using the jet-veto efficiency method, updated relative to earlier work to take into account what has been learnt from the new precision calculations that we include. For 13 TeV collisions and using our default choice for the renormalisation and factorisation scales, ${\mu }_0=m_H/2$, the matched prediction for the jet-veto efficiency increases the pure NNNLO prediction by about 2% and the two have comparable uncertainties. Relative to NNLO+NNLL results, the new prediction is 2% smaller and the uncertainty reduces from more than 10% to less than 5%. Results are also presented for the central scale ${\mu }_0=m_H$.

    hep-phhep-exJHEP(2016)·118 citations
11. 11*

    Dirac form factors and electric charge radii of baryons in the combined chiral and 1/N_c expansions

    Ruben Flores-Mendieta🇲🇽 · Mayra Alejandra Rivera-Ruiz🇲🇽

    The baryon Dirac form factor is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of color charges. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference are accounted for. There are large-N_c cancellations between different one-loop graphs as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. As a byproduct, the mean-square charge radius is also computed through a detailed numerical analysis. The predictions of large-N_c baryon chiral perturbation theory are in very good agreement both with the expectations from the 1/N_c expansion and with the experimental data.

    hep-phPRD(2015)·14 citations
12. 12*

    Towards precise top mass measurement at LHC

    Sayaka Kawabata🇯🇵

    The top quark mass plays an important role in a variety of discussions both within and beyond the Standard Model. However, a precise determination of a theoretically well-defined top quark mass is still missing. Towards a precise determination of a theoretically well-defined top quark mass at the LHC, we propose a method which uses lepton energy distribution and has a boost-invariant nature. We investigate its experimental viability by performing a simulation analysis for ttbar production process and lepton+jets decay channel at the leading order. We estimate several major uncertainties in the top mass determination with this method and they amount to 1.7 GeV with an integrated luminosity of 100 fb^{-1} at sqrt{s}=14 TeV. The uncertainties should be reduced by considering the next-to-leading order corrections to the method.

    hep-phhep-exNucl.Part.Phys.Proc.(2016)·0 citations
13. 13*

    The effect of the chiral chemical potential on the chiral phase transition in the NJL model with different regularization schemes

    Lang Yu🇨🇳 · Hao Liu🇨🇳 · Mei Huang🇨🇳

    We study the chiral phase transition in the presence of the chiral chemical potential ${\mu }_5$ using the two-flavor Nambu--Jona-Lasinio model. In particular, we analyze the reason why one can obtain two opposite behaviors of the chiral critical temperature as a function of ${\mu }_5$ in the framework of different regularization schemes. We compare the modifications of the chiral condensate and the critical temperature due to ${\mu }_5$ in different regularization schemes, analytically and numerically. Finally, we find that, for the conventional hard-cutoff regularization scheme, the increasing dependence of the critical temperature on the chiral chemical potential is an artifact, which is caused by the fact that it does not include complete contribution from the thermal fluctuations. When the thermal contribution is fully taken into account, the chiral critical temperature should decrease with ${\mu }_5$.

    hep-phhep-latnucl-thPRD(2016)·69 citations
14. 14*

    Coherent production of the long-lived pionium nP states in relativistic nucleus-nucleus collisions

    S Gevorkyan · O Voskresenskaya🇷🇺

    The coherent production of the nP states of the ${\pi }^{+}{\pi }^{-}$ atoms ($A_{2\pi }$) in relativistic nucleus-nucleus collisions is considered as a possible source of the $A_{2\pi }(nP)$ beam for the pionium Lamb-shift measurement. A general expression for estimation of the $A_{2\pi }(nP)$ yield is derived in the framework of the equivalent photon approximation.

    hep-ph0 citations
15. 15*

    Dilaton assisted two-field inflation from no-scale supergravity

    Girish Kumar Chakravarty🇮🇳 · Suratna Das🇮🇳 · Gaetano Lambiase🇮🇹 · Subhendra Mohanty🇮🇳

    We present a two-field inflation model where inflaton field has a non-canonical kinetic term due to the presence of a dilaton field. It is a two-parameter generalization of one-parameter Brans-Dicke gravity in the Einstein frame. We show that in such an inflation model the quartic and quadratic inflaton potentials, which are otherwise ruled out by the present Planck-{\it Keck}/BICEP2 data, yield scalar spectral index and tensor-to-scalar ratio in accordance with the present data. Such a model yield tensor-to-scalar ratio of the order of $10^{-2}$ which is within the reach of $B-$mode experiments like {\it Keck}/BICEP3, CMBPol and thus can be put to test in the near future. This model yields negligible non-Gaussianity and no isocurvature perturbations upto slow-roll approximation. Finally, we show that such a model can be realised in the realm of no-scale supergravity.

    hep-phastro-ph.COgr-qcPRD(2016)·12 citations
16. 16*

    Dark Matter phenomenology of GUT Inspired simplified models

    Giorgio Arcadi🇫🇷

    We discuss some aspects of dark matter phenomenology, in particular related to Direct detection and collider searches, of models in which a fermionic Dark Matter interacts with SM fermions through spin 1 mediators. Contrary to conventional simplified models we will consider fixed assignments of the couplings of the ($Z^{{}^{\prime }}$) mediator, according theoretically motivated embeddings. This allows to predict signals at future experimental facilities which can be used to test and possibly discriminate different realizations.

    hep-phJ.Phys.Conf.Ser.(2016)·2 citations
17. 17*

    Dark Matter and Baryon Asymmetry production from out-of-equilibrium decays of Supersymmetric states

    Giorgio Arcadi🇫🇷

    We will review the main aspects of a mechanism for the contemporary generation of the baryon and Dark Matter abundances from the out-of-equilibrium decay of a Wimp-like mother particle and briefly discuss a concrete realization in a Supersymmetric scenario.

    hep-phJ.Phys.Conf.Ser.(2016)·1 citation
18. 18*

    Will protons become gray at 13 TeV and 100 TeV?

    I.M. Dremin🇷🇺

    It is shown that the regime of pp-interactions at 7 TeV is a critical one. The LHC data about elastic pp-scattering at 7 and 8 TeV are used to get some information about both elastic and inelastic profiles of pp-collisions. They are discussed in the context of two phenomenological models which pretend to describe the high energy pp-data with high accuracy. Some predictions following from these models for LHC energy 13 TeV and for energy 95 TeV of the newly proposed collider are discussed. It is claimed that the center of the inelastic interaction region will become less dark with increase of energy albeit very slowly.

    hep-phhep-exnucl-exnucl-thBull.Lebedev Phys.Inst.(2017)·9 citations
19. 19*

    Tests of Pythia8 Rescattering Model

    Tasnuva Chowdhury🇧🇩 · Deepak Kar🇿🇦

    One of the most poorly understood phenomenon in hadron collisions, is the so called multiple parton interaction (MPI). Apart from one quark or gluon each from each colliding proton, additional quarks or gluons can interact as well, and these can not be calculated from first principles. The concept of rescattering has been introduced recently in Pythia8 event generator, where particles originating from these secondary interactions can interact again with quarks or gluons from incoming protons. In this paper, we look at events with a $Z$-boson, to find observables which can potentially be sensitive to this rescattering effect. While jet-balance observables do not show visible difference, charged particle distributions in different azimuthal regions show some difference. The parameters controlling MPI can be tuned to give a good description of data with rescattering.

    hep-ph0 citations
20. 20*

    Di-hadron fragmentation and mapping of the nucleon structure

    Silvia Pisano🇮🇹 · Marco Radici🇮🇹

    The fragmentation of a colored parton directly into a pair of colorless hadrons is a non-perturbative mechanism that offers important insights into the nucleon structure. Di-hadron fragmentation functions can be extracted from semi-inclusive electron-positron annihilation data. They also appear in observables describing the semi-inclusive production of two hadrons in deep-inelastic scattering of leptons off nucleons or in hadron-hadron collisions. When a target nucleon is transversely polarized, a specific chiral-odd di-hadron fragmentation function can be used as the analyzer of the net density of transversely polarized quarks in a transversely polarized nucleon, the so-called transversity distribution. The latter can be extracted through suitable single-spin asymmetries in the framework of collinear factorization, thus in a much simpler framework with respect to the traditional one in single-hadron fragmentation. At subleading twist, the same chiral-odd di-hadron fragmentation function provides the cleanest access to the poorly known twist-3 parton distribution $e(x)$, which is intimately related to the mechanism of dynamical chiral symmetry breaking in QCD. When sensitive to details of transverse momentum dynamics of partons, the di-hadron fragmentation functions for a longitudinally polarized quark can be connected to the longitudinal jet handedness to explore possible effects due to $CP-$violation of the QCD vacuum. In this review, we outline the formalism of di-hadron fragmentation functions, we discuss different observables where they appear and we present measurements and future worldwide plans.

    hep-phhep-exnucl-exnucl-thEPJA(2016)·21 citations
21. 21*

    Observational effects of a running Planck mass

    Zhiqi Huang🇨🇦

    We consider observational effects of a running effective Planck mass in the scalar-tensor gravity theory. At the background level, an increasing effective Planck mass allows a larger Hubble constant $H_0$, which is more compatible with the local direct measurements. At the perturbative level, for cosmic microwave background (CMB) anisotropies, an increasing effective Planck mass ($i$) suppresses the unlensed CMB power at $\ell \lesssim 30$ via the integrated Sachs-Wolfe effect and ($ii$) enhances CMB lensing power. Both effects slightly relax the tension between the current CMB data from the Planck satellite and the standard $\Lambda$CDM model predictions. However, those impacts on the CMB secondary anisotropies are subdominant, and the overall constraints are driven by the background measurements. Combining CMB data from the Planck satellite and an $H_0$ prior from Riess $et$ $al$, we find a $\sim 2\sigma$ hint of a positive running of effective Planck mass. However, the hint goes away when we add other low-redshift observational data including type Ia supernovae, baryon acoustic oscillations and an Universe age estimation using the oldest stars.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2016)·33 citations
22. 22*

    Strong-coupling scales and the graph structure of multi-gravity theories

    James H. C. Scargill🇬🇧 · Johannes Noller🇬🇧

    In this paper we consider how the strong-coupling scale, or perturbative cutoff, in a multi-gravity theory depends upon the presence and structure of interactions between the different fields. This can elegantly be rephrased in terms of the size and structure of the `theory graph' which depicts the interactions in a given theory. We show that the question can be answered in terms of the properties of various graph-theoretical matrices, affording an efficient way to estimate and place bounds on the strong-coupling scale of a given theory. In light of this we also consider the problem of relating a given theory graph to a discretised higher dimensional theory, a la dimensional deconstruction.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2016)·15 citations
23. 23*

    Shift-Symmetries at Higher Order

    Steven Abel🇬🇧 · Richard J. Stewart🇬🇧

    The fate of shift-symmetries in effective string models is considered beyond tree-level. Such symmetries have been proposed in the past as a way to maintain a hierarchically small Higgs mass and also play a role in schemes of cosmological relaxation. It is argued that on general grounds one expects shift-symmetries to be restored in the limit of certain asymmetric compactifications, to all orders in perturbation theory. This behaviour is verified by explicit computation of the Kaehler potential to one-loop order.

    ↳ hep-thhep-phJHEP(2016)·8 citations
24. 24*

    Fermi-LAT Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center

    The Fermi-LAT Collaboration

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission towards the Galactic centre (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a $15^{\circ }\times 15^{\circ }$ region about the direction of the GC, and implications for the interstellar emissions produced by cosmic ray (CR) particles interacting with the gas and radiation fields in the inner Galaxy and for the point sources detected. Specialised interstellar emission models (IEMs) are constructed that enable separation of the gamma-ray emission from the inner $\sim 1$ kpc about the GC from the fore- and background emission from the Galaxy. Based on these models, the interstellar emission from CR electrons interacting with the interstellar radiation field via the inverse Compton (IC) process and CR nuclei inelastically scattering off the gas producing gamma-rays via ${\pi }^0$ decays from the inner $\sim 1$ kpc is determined. The IC contribution is found to be dominant in the region and strongly enhanced compared to previous studies. A catalog of point sources for the $15^{\circ }\times 15^{\circ }$ region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy point source Catalog (1FIG). After subtracting the interstellar emission and point-source contributions from the data a residual is found that is a sub-dominant fraction of the total flux. If spatial templates that peak toward the GC are used to model the positive residual and included in the total model for the $15^{\circ }\times 15^{\circ }$ region, the agreement with the data improves, but none of the additional templates account for all of the residual structure. The spectrum of the positive residual modelled with these templates has a strong dependence on the choice of IEM. [Abridged]

    ↳ astro-ph.HEhep-exhep-phApJ(2016)·541 citations
25. 25*

    (2+1)-flavor QCD Thermodynamics from the Gradient Flow

    Etsuko Itou🇯🇵 · Hiroshi Suzuki🇯🇵 · Yusuke Taniguchi🇯🇵 · Takashi Umeda🇯🇵

    Recently, we proposed a novel method to define and calculate the energy-momentum tensor (EMT) in lattice gauge theory on the basis of the Yang-Mills gradient flow [1]. In this proceedings, we summarize the basic idea and technical steps to obtain the bulk thermodynamic quantities in lattice gauge theory using this method for the quenched and $(2+1)$-flavor QCD. The revised results of integration measure (trace anomaly) and entropy density of the quenched QCD with corrected coefficients are shown. Furthermore, we also show the flow time dependence of the parts of EMT including the dynamical fermions. This work is based on a joint-collaboration between FlowQCD and WHOT QCD.

    ↳ hep-lathep-phnucl-thPoS(2016)·9 citations
26. 26*

    Localization of Gravitino Field on Thin Branes

    Yun-Zhi Du🇨🇳 · Li Zhao🇨🇳 · Xiang-Nan Zhou🇨🇳 · Yi Zhong🇨🇳 · Yu-Xiao Liu🇨🇳

    In this paper, we investigate the localization of a bulk gravitino field on the scalar-tensor branes and compare the result with that in the Randall-Sundrum-1 (RS1) model. The coupled chiral equations for the Kaluza-Klein (KK) modes of the gravitino field are obtained by fixing the gauge ${\Psi }_5=0$ and using the chiral KK decompositions. It is shown that, in the RS1 model for the left- and right-handed zero modes of the gravitino field, only one of them can be localized near one brane. For the massive modes, both chiral modes survive and the lower KK modes are localized near the IR brane from the four-dimensional physical coordinate point of view. However, for the scalar-tensor brane model, the localization of the gravitino chiral zero modes depends on the coupling parameter $\lambda$, and they will be not localized around anyone brane within a certain range of the parameter $\lambda$, which is quite different from the RS1 model. Furthermore, we also give the corresponding mass spectra of the massive KK gravitinos in the scalar-tensor model.

    ↳ hep-thhep-phAnnals Phys.(2018)·6 citations
27. 27*

    Electromagnetic recombination spectra at the quark-hadron phase transition

    Clint Young🇺🇸 · Scott Pratt🇺🇸

    When quarks hadronize, they accelerate. Because they carry electric charge, they must radiate light as they accelerate and hadronize. This is true not only in jets but also in heavy ion collisions, where a thermalized plasma of quarks and gluons cools into a gas of hadrons. First, direct emission of photons from two quarks coalescing into pions is calculated using the quark-meson model. The yield of final-state photons to pions is found to be about $e^2/g_{\pi qq}^2$, which is on the order of a percent. Second, the yield of photons from the decay of highly excited color singlets, which may exist ephemerally during hadronizaton, is estimated. Because these contributions occur late in the reaction, they should carry significant elliptic flow, which may help explain the large observed flow of direct photons at RHIC by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC). The enhanced emission also helps explain PHENIX's surprisingly large observed $\gamma /\pi$ ratio.

    ↳ nucl-thhep-phPRC(2016)·7 citations
28. 28*

    Building SO${}_{10}$- models with ${\mathbb{D}}_4$ symmetry

    R. Ahl Laamara🇲🇦 · M. Miskaoui🇲🇦 · E.H Saidi🇲🇦

    Using characters of finite group representations and monodromy of matter curves in F-GUT, we complete partial results in literature by building SO models with dihedral ${\mathbb{D}}_4$ discrete symmetry. We first revisit the ${\mathbb{S}}_4$-and ${\mathbb{S}}_3$-models from the discrete group character view, then we extend the construction to ${\mathbb{D}}_4$.\ We find that there are three types of $S{O}_{10}\times {\mathbb{D}}_4$ models depending on the ways the ${\mathbb{S}}_4$-triplets break down in terms of irreducible ${\mathbb{D}}_4$- representations: $\left(\alpha \right)$ as $1_{{}_{+,-}}\oplus 1_{{}_{+,-}}\oplus 1_{{}_{-,+}};$ or $\left(\beta \right)1_{{}_{+,+}}\oplus 1_{{}_{+,-}}\oplus 1_{{}_{-,-}};$ or also $\left(\gamma \right)$ $1_{{}_{+,-}}\oplus 2_{{}_{0,0}}$. Superpotentials and other features are also given.

    ↳ hep-thhep-phNPB(2015)·6 citations
29. 29*

    Projecting the graviton to probe higher or lower dimensions

    Anupam Mazumdar🇬🇧 · Spyridon Talaganis🇬🇧

    In this paper, we will discuss how in Einstein's theory a graviton can be enforced to probe fewer space-time dimensions in the deep ultraviolet (UV) as compared to far infrared (IR), and vice-versa. In particular, from a $D$ dimensional gravitational action in the IR we can project the $D$ dimensional graviton to probe only $2\le N\le D-1$ dimensions in the deep UV. Such projections of a graviton propagator can be thought of as an alternative to compactification. We will briefly explain the physical interpretation and consequences of such a dimensional transmutation.

    ↳ hep-thgr-qchep-ph0 citations
30. 30*

    Primordial Statistical Anisotropies: The Effective Field Theory Approach

    Ali Akbar Abolhasani🇮🇷 · Mohammad Akhshik🇮🇷 · Razieh Emami🇨🇳 · Hassan Firouzjahi🇮🇷

    In this work we present the effective field theory of primordial statistical anisotropies generated during anisotropic inflation involving a background $U(1)$ gauge field. Besides the usual Goldstone boson associated with the breaking of time diffeomorphism we have two additional Goldstone bosons associated with the breaking of spatial diffeomorphisms. We further identify these two new Goldstone bosons with the expected two transverse degrees of the $U(1)$ gauge field fluctuations. Upon defining the appropriate unitary gauge, we present the most general quadratic action which respects the remnant symmetry in the unitary gauge. The interactions between various Goldstone bosons leads to statistical anisotropy in curvature perturbation power spectrum. Calculating the general results for power spectrum anisotropy, we recover the previously known results in specific models of anisotropic inflation. In addition, we present novel results for statistical anisotropy in models with non-trivial sound speed for inflaton fluctuations. Also we identify the interaction which leads to birefringence-like effects in anisotropic power spectrum in which the speed of gauge field fluctuations depends on the direction of the mode propagation and the two polarization of gauge field fluctuations contribute differently in statistical anisotropy. As another interesting application, our EFT approach naturally captures interactions generating parity violating statistical anisotropies.

    ↳ astro-ph.COhep-phhep-thJCAP(2016)·43 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.