Thu·Aug 4, 2016Thursday·August 4, 2016

1. 01*

   Effective Field Theory with Two Higgs Doublets

   Andreas Crivellin🇨🇭 · Margherita Ghezzi🇨🇭 · Massimiliano Procura🇨🇭

   In this article we extend the effective field theory framework describing new physics effects to the case where the underlying low-energy theory is a Two-Higgs-Doublet model. We derive a complete set of independent operators up to dimension six assuming a $Z_2$-invariant CP-conserving Higgs potential. The effects on Higgs and gauge boson masses, mixing angles in the Higgs sector as well as couplings to fermions and gauge bosons are computed. At variance with the case of a single Higgs doublet, we find that pair production of SM-like Higgses, arising through dimension-six operators, is not fixed by fermion-fermion-Higgs couplings and can therefore be sizable.

   hep-phJHEP(2016)·47 citations
2. 02*

   Resolving gluon fusion loops at current and future hadron colliders

   Aleksandr Azatov🇮🇹 · Christophe Grojean🇩🇪 · Ayan Paul🇮🇹 · Ennio Salvioni🇺🇸

   Inclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics effects. Using an Effective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including $t\bar{t}h$ and boosted, off-shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. In addition, we revisit off-shell Higgs production. Firstly, we point out its sensitivity to modifications of the top-$Z$ couplings, and by means of a general analysis we show that the reach is comparable to that of tree-level processes such as $t\bar{t}Z$ production. Implications for composite Higgs models are also discussed. Secondly, we assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark.

   hep-phhep-exJHEP(2016)·68 citations
3. 03*

   SU(3) Polyakov linear-sigma model: bulk and shear viscosity of QCD matter in finite magnetic field

   Abdel Nasser Tawfik🇪🇬 · Abdel Magied Diab (Egyptian Ctr. Theor. Phys., Cairo, WLCAPP, Cairo)🇪🇬 · T. M. Hussein (Cairo U.)🇪🇬

   Due to off-center relativistic motion of the charged spectators and the local momentum-imbalance of the participants, a short-lived huge magnetic field is likely generated, especially in relativistic heavy-ion collisions. In determining the temperature dependence of bulk and shear viscosities of the QCD matter in vanishing and finite magnetic field, we utilize mean field approximation to the SU($3$) Polyakov linear-sigma model (PLSM). We compare between the results from two different approaches; Green-Kubo correlation and Boltzmann master equation with Chapman-Enskog expansion. We find that both approaches have almost identical results, especially in the hadron phase. In the temperature dependence of bulk and shear viscosities relative to thermal entropy at the critical temperature, there is a rapid decrease in the chiral phase-transition and in the critical temperature with increasing magnetic field. As the magnetic field strength increases, a peak appears at the critical temperature ($T_c$). This can be understood from the small drop on the thermal entropy at $T_c$, which can be interpreted due to instability in the hydrodynamic flow of the quark-gluon plasma and soft statistical hadronization. It is obvious that, increasing magnetic field accelerates the transition from hadron to QGP phases (inverse catalysis), i.e., taking place at lower temperatures.

   hep-phhep-lathep-thInt.J.Adv.Res.Phys.Sci.(2016)·8 citations
4. 04*

   Light dark photon and fermionic dark radiation for the Hubble constant and the structure formation

   P. Ko🇰🇷 · Yong Tang🇰🇷

   Motivated by the tensions in the Hubble constant $H_0$ and the structure growth ${\sigma }_8$ between $Planck$ results and other low redshift measurements, we discuss some cosmological effects of a dark sector model in which dark matter (DM) interacts with fermionic dark radiation (DR) through a light gauge boson (dark photon). Such kind of models are very generic in particle physics with a dark sector with dark gauge symmetries. The effective number of neutrinos is increased by $\delta N_{eff}\sim 0.5$ due to light dark photon and fermionic DR, thereby resolving the conflicts in $H_0$. The elastic scattering between DM and DR induces suppression for DM's density perturbation, but without acoustic oscillations. For weakly-interacting DM around $100$GeV, the new gauge coupling should be $\sim 10^{-4}$ to have sizable effect on matter power spectrum in order to relax the tension in ${\sigma }_8$.

   hep-phastro-ph.COPLB(2016)·95 citations
5. 05*

   Astrophysical aspects of neutrino dynamics in ultra-degenerate quark gluon plasma

   Souvik Priyam Adhya🇮🇳

   The cardinal focus of the present review is to explore the role of neutrinos originating from the ultra-dense core of neutron stars composed of quark gluon plasma in the astrophysical scenario. The collective excitations of the quarks involving the neutrinos through the different kinematical processes have been studied. The cooling of the neutron stars as well as pulsar kicks due to asymmetric neutrino emission have been discussed in detail. Results involving calculation of relevant physical quantities like neutrino mean free path and emissivity have been presented in the framework of non-Fermi liquid behavior as applicable to ultra-degenerate plasma.

   hep-phAdv.High Energy Phys.(2017)·4 citations
6. 06*

   Charge and longitudinal momentum distributions in transverse coordinate space

   Chandan Mondal🇮🇳 · Narinder Kumar🇮🇳 · Harleen Dahiya🇮🇳 · Dipankar Chakrabarti🇮🇳

   We investigate the charge distributions for the $u$ and $d$ quarks in transverse coordinate space in a light-front quark-diquark model for the nucleons using the overlaps of the wave functions constructed from the soft-wall AdS/QCD prediction. We have also obtained the charge distributions for proton and neutron in transverse coordinate space and compared it with the distributions obtained in impact-parameter space. Further, we study the longitudinal momentum distributions using the wave functions in the transverse coordinate space. We have also shown the explicit fermionic and bosonic contributions for different struck $u$ and $d$ quarks.

   hep-phPRD(2016)·19 citations
7. 07*

   Consistent regularization and renormalization in models with inhomogeneous phases

   Prabal Adhikari🇺🇸 · Jens O. Andersen🇳🇴

   In many models in condensed matter physics and high-energy physics, one finds inhomogeneous phases at high density and low temperature. These phases are characterized by a spatially dependent condensate or order parameter. A proper calculation requires that one takes the vacuum fluctuations of the model into account. These fluctuations are ultraviolet divergent and must be regularized. We discuss different consistent ways of regularizing and renormalizing quantum fluctuations, focusing on a symmetric energy cutoff scheme and dimensional regularization. We apply these techniques calculating the vacuum energy in the NJL model in 1+1 dimensions in the large-$N_c$ limit and the 3+1 dimensional quark-meson model in the mean-field approximation both for a one-dimensional chiral-density wave.

   hep-phPRD(2017)·11 citations
8. 08*

   Solving the Standard Model Problems in Softened Gravity

   Alberto Salvio🇨🇭

   The Higgs naturalness problem is solved if the growth of Einstein's gravitational interaction is softened at an energy $\lesssim 10^{11}$GeV (softened gravity). We work here within an explicit realization where the Einstein-Hilbert Lagrangian is extended to include terms quadratic in the curvature and a non-minimal coupling with the Higgs. We show that this solution is preserved by adding three right-handed neutrinos with masses below the electroweak scale, accounting for neutrino oscillations, dark matter and the baryon asymmetry. The smallness of the right-handed neutrino masses (compared to the Planck scale) and the QCD $\theta$-term are also shown to be natural. We prove that a possible gravitational source of CP violation cannot spoil the model, thanks to the presence of right-handed neutrinos. Inflation is approximately described by the Starobinsky model in this context, and can occur even if we live in a metastable vacuum.

   hep-phgr-qcPRD(2016)·46 citations
9. 09*

   Full mass dependence in Higgs boson production in association with jets at the LHC and FCC

   Nicolas Greiner🇨🇭 · Stefan Hoeche🇺🇸 · Gionata Luisoni🇨🇭 · Marek Schonherr🇨🇭 · Jan-Christopher Winter🇺🇸

   The first computation of Higgs production in association with three jets at NLO in QCD has recently been performed using the effective theory, where the top quark is treated as an infinitely heavy particle and integrated out. This approach is restricted to the regions in phase space where the typical scales are not larger than the top quark mass. Here we investigate this statement at a quantitative level by calculating the leading-order contributions to the production of a Standard Model Higgs boson in association with up to three jets taking full top-quark and bottom-quark mass dependence into account. We find that the transverse momentum of the hardest particle or jet plays a key role in the breakdown of the effective theory predictions, and that discrepancies can easily reach an order of magnitude for transverse momenta of about 1 TeV. The impact of bottom-quark loops are found to be visible in the small transverse momentum region, leading to corrections of up to 5 percent. We further study the impact of mass corrections when VBF selection cuts are applied and when the center-of-mass energy is increased to 100 TeV.

   hep-phJHEP(2017)·40 citations
10. 10*

    Thermo-magnetic nonlocal NJL model in the real and imaginary time formalisms

    F. Márquez🇨🇱 · R. Zamora🇨🇱

    In this article we study a nonlocal Nambu--Jona-Lasinio (nNJL) model with a Gaussian regulator in presence of a uniform magnetic field. We take a mixed approach to the incorporation of temperature in the model, and consider aspects of both real and imaginary time formalisms. We include confinement in the model through the quasiparticle interpretation of the poles of the propagator. The effect of the magnetic field in the deconfinement phase transition is then studied. It is found that, like with chiral symmetry restoration, magnetic catalysis occurs for the deconfinement phase transition. It is also found that the magnetic field enhances the thermodynamical instability of the system. We work in the weak field limit, i.e. $(eB)<5m_{\pi }^2$. At this level there is no splitting of the critical temperatures for chiral and deconfinement phase transitions.

    hep-phhep-thInt.J.Mod.Phys.A(2017)·1 citation
11. 11*

    Using an intense laser beam in interaction with muon/electron beam to probe the Noncommutative QED

    S. Tizchang🇮🇷 · S. Batebi🇮🇷 · M. Haghighat🇮🇷 · R. Mohammadi🇮🇷

    It is known that the linearly polarized photons can partly transform to circularly polarized ones via forward Compton scattering in a background such as the external magnetic field or noncommutative space time. Based on this fact we explore the effects of the NC-background on the scattering of a linearly polarized laser beam from an intense beam of charged leptons. We show that for a muon/electron beam flux ${\bar{\epsilon }}_{\mu ,e}\sim 10^{12}/10^{10}\mathrm{TeV}{\mathrm{cm}}^{-2}{\sec }^{-1}$ and a linearly polarized laser beam with energy $k^0\sim$1 eV and average power ${\bar{P}}_{\mathrm{laser}}\simeq$1 MW, the generation rate of circularly polarized photons is about $R_{{}_V}\sim 10^4/\sec$ for Noncommutative energy scale ${\Lambda }_{NC}\sim 10$TeV. This is fairly large and can grow for more intense beams in near future.

    hep-phhep-thJHEP(2017)·8 citations
12. 12*

    Exponential parameterization of neutrino mixing matrix with account for CP-violation data

    K.Zhukovsky · F.M.Murilio

    The exponential parameterization of Pontecorvo-Maki-Nakagawa-Sakata mixing matrix for neutrino is discussed. The exponential form allows easy factorization and separate analysis of the CP-violating and Majorana terms. Based upon the recent experimental data on the neutrino mixing, the values for the exponential parameterization matrix for neutrinos are determined. The matrix entries for the pure rotational part in charge of the mixing without CP-violation are derived. The complementarity hypothesis for quarks and neutrinos is demonstrated. The comparison of the results, based on most recent and on old data is held. The CP-violating parameter value is estimated, based on the so far imprecise experimental indications, regarding CP-violation for neutrinos. The unitarity of the exponential parameterisation and the CP-violating term transform is confirmed. The transform of the neutrino mass state vector by the exponential matrix with account for CP-violation is shown.

    hep-phEPJC(2016)·12 citations
13. 13*

    $\mathcal{KK}\text{MC-hh}$: Resummed Exact $\mathcal{O}({\alpha }^{2}L)$ EW Corrections in a Hadronic MC Event Generator

    S. Jadach (1)🇵🇱 · B.F.L. Ward (2)🇺🇸 · Z. A. Was (1)🇵🇱 · S.A. Yost (3) ((1) Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland, (2) Baylor University, Waco, TX, USA, (3) The Citadel, Charleston, SC, USA)🇺🇸

    We present an improvement of the MC event generator Herwiri2, where we recall the latter MC was a prototype for the inclusion of CEEX resummed EW corrections in hadron-hadron scattering at high cms energies. In this improvement the new exact $\mathcal{O}({\alpha }^{2}L)$ resummed EW generator $\mathcal{KK}$ MC 4.22, featuring as it does the CEEX realization of resummation in the EW sector, is put in union with the Herwig parton shower environment. The {\rm LHE} format of the attendant output event file means that all other conventional parton shower environments are available to the would-be user of the resulting new MC. For this reason (and others -- see the text) we henceforth refer to the new improvement of the Herwiri2 MC as $\mathcal{KK}\text{MC-hh}$. Since this new MC features exact $\mathcal{O}(\alpha )$ pure weak corrections from the DIZET EW library and features the CEEX and the EEX YFS-style resummation of large multiple photon effects, it provides already the concrete path to 0.05\% precision on such effects if we focus on the EW effects themselves. We therefore show predictions for observable distributions and comparisons with other approaches in the literature. This MC represents an important step in the realization of the exact amplitude-based $QED\otimes QCD$ resummation paradigm. Independently of this latter observation, the MC rigorously quantifies important EW effects in the current LHC experiments.

    hep-phPRD(2016)·34 citations
14. 14*

    Measurement of the ionization produced by sub-keV silicon nuclear recoils in a CCD dark matter detector

    A.E. Chavarria🇺🇸 · J.I. Collar🇺🇸 · J.R. Peña🇺🇸 · P. Privitera🇺🇸 · A.E. Robinson🇺🇸 · B. Scholz🇺🇸 · C. Sengul🇺🇸 · J. Zhou🇺🇸 · J. Estrada🇺🇸 · F. Izraelevitch🇺🇸 · J. Tiffenberg🇺🇸 · J.R.T. de Mello Neto🇧🇷 · D. Torres Machado🇧🇷

    We report a measurement of the ionization efficiency of silicon nuclei recoiling with sub-keV kinetic energy in the bulk silicon of a charge-coupled device (CCD). Nuclear recoils are produced by low-energy neutrons ($<$24 keV) from a ${}^{124}$Sb-${}^9$Be photoneutron source, and their ionization signal is measured down to 60 eV electron equivalent. This energy range, previously unexplored, is relevant for the detection of low-mass dark matter particles. The measured efficiency is found to deviate from the extrapolation to low energies of the Lindhard model. This measurement also demonstrates the sensitivity to nuclear recoils of CCDs employed by DAMIC, a dark matter direct detection experiment located in the SNOLAB underground laboratory.

    ↳ astro-ph.IMastro-ph.COhep-exhep-ph+1PRD(2016)·99 citations
15. 15*

    Event simulation based on three-fluid hydrodynamics for collisions at energies available at the Dubna Nuclotron-based Ion Collider Facility and at the Facility for Antiproton and Ion Research in Darmstadt

    P. Batyuk🇷🇺 · D. Blaschke🇷🇺 · M. Bleicher🇩🇪 · Yu. B. Ivanov🇷🇺 · Iu. Karpenko🇺🇦 · S. Merts🇷🇺 · M. Nahrgang🇺🇸 · H. Petersen🇩🇪 · O. Rogachevsky🇷🇺

    We present a new event generator based on the three-fluid hydrodynamics approach for the early stage of the collision, followed by a particlization at the hydrodynamic decoupling surface to join to a microscopic transport model, UrQMD, to account for hadronic final state interactions. We present first results for nuclear collisions of the FAIR/NICA energy scan program (Au+Au collisions, $\sqrt{s_{NN}}=4-11$ GeV). We address the directed flow of protons and pions as well as the proton rapidity distribution for two model EoS, one with a first order phase transition the other with a crossover type softening at high densities. The new simulation program has the unique feature that it can describe a hadron-to-quark matter transition which proceeds in the baryon stopping regime that is not accessible to previous simulation programs designed for higher energies.

    ↳ nucl-thhep-phPRC(2016)·58 citations
16. 16*

    On the spin excitation energy of the nucleon in the Skyrme model

    C. Adam🇪🇸 · J. Sanchez-Guillen🇪🇸 · A. Wereszczynski🇵🇱

    In the Skyrme model of nucleons and nuclei, the spin excitation energy of the nucleon is traditionally calculated by a fit of the rigid rotor quantization of spin/isospin of the fundamental Skyrmion (the hedgehog) to the masses of the nucleon and the Delta resonance. The resulting, quite large spin excitation energy of the nucleon of about $73\text{mbox}MeV$ is, however, rather difficult to reconcile with the small binding energies of physical nuclei, among other problems. Here we argue that a more reliable value for the spin excitation energy of the nucleon, compatible with many physical constraints, is about $16\text{mbox}MeV$. The fit of the rigid rotor to the Delta, on the other hand, is problematic in any case, because it implies the use of a nonrelativistic method for a highly relativistic system.

    ↳ nucl-thhep-phIJMPE(2016)·8 citations
17. 17*

    Chiral Magnetic Effect Task Force Report

    Vladimir Skokov🇺🇸 · Paul Sorensen🇺🇸 · Volker Koch🇺🇸 · Soeren Schlichting🇺🇸 · Jim Thomas🇺🇸 · Sergei Voloshin🇺🇸 · Gang Wang🇺🇸 · Ho-Ung Yee🇺🇸

    In this report, we briefly examine the current status of the study of the chiral magnetic effect including theory and experimental progress. We recommend future strategies for resolving uncertainties in interpretation including recommendations for theoretical work, recommendations for measurements based on data collected in the past five years, and recommendations for beam use in the coming years of RHIC. We have specifically investigated the case for colliding nuclear isobars (nuclei with the same mass but different charge) and find the case compelling. We recommend that a program of nuclear isobar collisions to isolate the chiral magnetic effect from background sources be placed as a high priority item in the strategy for completing the RHIC mission.

    ↳ nucl-thhep-phnucl-exCPC(2017)·162 citations
18. 18*

    The Equation of State and Duration to Radiation Domination After Inflation

    Kaloian D. Lozanov🇬🇧 · Mustafa A. Amin🇺🇸

    We calculate the equation of state after inflation and provide an upper bound on the duration before radiation domination by taking the nonlinear dynamics of the fragmented inflaton field into account. A broad class of single-field inflationary models with observationally consistent flattening of the potential at a scale $M$ away from the origin, $V(\varphi )\propto |\varphi {|}^{2n}$ near the origin, and where the couplings to other fields are ignored are included in our analysis. We find that the equation of state parameter $w\to 0$ for $n=1$ and $w\to 1/3$ (after sufficient time) for $n\gtrsim 1$. We calculate how the number of $e$-folds to radiation domination depends on both $n$ and $M$ when $M\sim m_{\mathrm{pl}}$, whereas when $M\ll m_{\mathrm{pl}}$, we find that the duration to radiation domination is negligible. Our results are explained in terms of a linear instability analysis in an expanding universe, scaling arguments, and are supported by detailed 3+1 dimensional lattice simulations. We show how our work significantly reduces the uncertainty in inflationary observables, even after including couplings to additional light fields.

    ↳ astro-ph.COhep-phhep-thPRL(2017)·224 citations
19. 19*

    Ultraviolet cutoffs and the photon mass

    Piotr H. Chankowski (Warsaw U.)🇵🇱 · Adrian Lewandowski (Potsdam, Max Planck Inst. and Warsaw U.)🇩🇪 · Krzysztof A. Meissner (Warsaw U.)🇵🇱

    The momentum UV cutoff in Quantum Field Theory is usually treated as an auxiliary device allowing to obtain finite amplitudes satisfying all physical requirements. It is even absent (not explicit) in the most popular approach - the dimensional regularization. We point out that the momentum cutoff treated as a bona fide physical scale, presumably equal or related to the Planck scale, would lead to unacceptable predictions. One of the dangers is a non-zero mass of the photon. In the naive approach, even with the cutoff equal to the Planck scale, this mass would grossly exceed the existing experimental bounds. We present the actual calculation using a concrete realization of the physical cutoff and speculate about the way to restore gauge symmetry order by order in the inverse powers of the cutoff scale.

    ↳ hep-thhep-phActa Phys.Polon.B(2017)·7 citations
20. 20*

    Constraining neutrino mass and extra relativistic degrees of freedom in dynamical dark energy models using Planck 2015 data in combination with low-redshift cosmological probes: basic extensions to $\Lambda$CDM cosmology

    Ming-Ming Zhao🇨🇳 · Yun-He Li🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    We investigate how the properties of dark energy affect the cosmological measurements of neutrino mass and extra relativistic degrees of freedom. We limit ourselves to the most basic extensions of $\Lambda$ cold dark matter (CDM) model, i.e. the $w$CDM model with one additional parameter $w$, and the $w_0{w}_a$CDM model with two additional parameters, $w_0$ and $w_a$. In the cosmological fits, we employ the 2015 cosmic microwave background temperature and polarization data from the Planck mission, in combination with low-redshift measurements such as the baryon acoustic oscillations, Type Ia supernovae and the Hubble constant ($H_0$). Given effects of massive neutrinos on large-scale structure, we further include weak lensing, redshift space distortion, Sunyaev--Zeldovich cluster counts and Planck lensing data. We show that, though the cosmological constant $\Lambda$ is still consistent with the current data, a phantom dark energy ($w<-1$) or an early phantom dark energy (i.e. quintom evolving from $w<-1$ to $w>-1$) is slightly more favoured by current observations, which leads to the fact that in both $w$CDM and $w_0{w}_a$CDM models we obtain a larger upper limit of $\sum m_{\nu }$. We also show that in the three dark energy models, the constraints on $N_{\mathrm{eff}}$ are in good accordance with each other, all in favour of the standard value 3.046, which indicates that the dark energy parameters almost have no impact on constraining $N_{\mathrm{eff}}$. Therefore, we conclude that the dark energy parameters can exert a significant influence on the cosmological weighing of neutrinos, but almost cannot affect the constraint on dark radiation.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2017)·60 citations
21. 21*

    Thermal Effects on Decays of a Metastable Brane Configuration

    Yuichiro Nakai🇺🇸 · Yutaka Ookouchi🇯🇵

    We study thermal effects on a decay process of a false vacuum in type IIA string theory. At finite temperature, the potential of the theory is corrected and also thermally excited modes enhance the decay rate. The false vacuum can accommodate a string-like object. This cosmic string makes the bubble creation rate much larger and causes an inhomogeneous vacuum decay. We investigate thermal corrections to the DBI action for the bubble/string bound state and discuss a thermally assisted tunneling process. We show that thermally excited states enhance the tunneling rate of the decay process, which makes the life-time of the false vacuum much shorter.

    ↳ hep-thhep-phPLB(2016)·6 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.