Thu·Nov 9, 2017Thursday·November 9, 2017

1. 01*

   The Light Radion Window

   Fayez Abu-Ajamieh🇺🇸 · Jun Seok Lee🇺🇸 · John Terning🇺🇸

   Inspired by the Contino-Pomarol-Rattazzi mechanism we explore scenarios with a very light (100 keV to 10 GeV) radion which could be associated with the suppression of the electroweak contribution to vacuum energy. We construct explicit, realistic models that realize this mechanism and explore the phenomenological constraints on this class of models. Compared with axion-like particles in this mass range, the bounds from SN 1987a and from cosmology can be much weaker, depending on the the mass of the radion and its coupling to other particles. With couplings suppressed by a scale lower than 100 TeV much of the mass window from 100 keV to 10 GeV is still open.

   hep-phastro-ph.COJHEP(2018)·23 citations
2. 02*

   Holographic Inclusive Central Particle Production at the LHC

   Richard Nally🇺🇸 · Timothy Raben🇺🇸 · Chung-I Tan🇺🇸

   We describe how the holographic, BPST Pomeron can be used to describe inclusive central production at the LHC.

   hep-phhep-th1 citation
3. 03*

   Optimal observables for $Z^{\prime }$ models in annihilation leptonic processes

   Alexey Gulov🇺🇦 · Yaroslav Moroz🇺🇦

   The optimal observables with the best ratio of signal to statistical uncertainty are proposed for a bunch of popular models of the $Z^{\prime }$ boson. They are the cross sections integrated over the phase space of the final particles with proper weight functions. It is shown that the proposed observables are completely equivalent to the ${\chi }^2$ fit of the differential cross section, so they could be used as an alternative of aggregating events into bins with further minimization of the ${\chi }^2$ function, especially in preliminary analysis of experimental data. Application of the observables to the maximum likelihood estimate of the $Z^{\prime }$ mass and the $Z$--$Z^{\prime }$ mixing angle as well as to the exclusion reach and statistical efficiency of the signal is investigated in details.

   hep-phPRD(2018)·4 citations
4. 04*

   Flavor effects in leptogenesis

   P. S. Bhupal Dev🇺🇸 · Pasquale Di Bari🇬🇧 · Bjorn Garbrecht🇩🇪 · Stéphane Lavignac🇫🇷 · Peter Millington🇬🇧 · Daniele Teresi🇧🇪

   Flavor effects can have a significant impact on the final estimate of the lepton (and therefore baryon) asymmetry in scenarios of leptogenesis. It is therefore necessary to account fully for this flavor dynamics in the relevant transport equations that describe the production (and washout) of the asymmetry. Doing so can both open up and restrict viable regions of parameter space relative to the predictions of more approximate calculations. In this review, we identify the regimes in which flavor effects can be relevant and illustrate their impact in a number of phenomenological models. These include type I and type II seesaw embeddings, and low-scale resonant scenarios. In addition, we provide an overview of the semi-classical and field-theoretic methods that have been developed to capture flavor effects in a consistent way.

   hep-phInt.J.Mod.Phys.A(2018)·125 citations
5. 05*

   ARS Leptogenesis

   M. Drewes🇧🇪 · B. Garbrecht🇩🇪 · P. Hernandez🇪🇸 · M. Kekic🇪🇸 · J. Lopez-Pavon🇨🇭 · J. Racker🇦🇷 · N. Rius🇪🇸 · J. Salvado🇪🇸 · D. Teresi🇧🇪

   We review the current status of the leptogenesis scenario originally proposed by Akhmedov, Rubakov and Smirnov (ARS). It takes place in the parametric regime where the right-handed neutrinos are at the electroweak scale or below and the CP-violating effects are induced by the coherent superposition of different right-handed mass eigenstates. Two main theoretical approaches to derive quantum kinetic equations, the Hamiltonian time evolution as well as the Closed-Time-Path technique are presented, and we discuss their relations. For scenarios with two right-handed neutrinos, we chart the viable parameter space. Both, a Bayesian analysis, that determines the most likely configurations for viable leptogenesis given different variants of flat priors, and a determination of the maximally allowed mixing between the light, mostly left-handed, and heavy, mostly right-handed, neutrino states are discussed. Rephasing invariants are shown to be a useful tool to classify and to understand various distinct contributions to ARS leptogenesis that can dominate in different parametric regimes. While these analyses are carried out for the parametric regime where initial asymmetries are generated predominantly from lepton-number conserving, but flavor violating effects, we also review the contributions from lepton-number violating operators and identify the regions of parameter space where these are relevant.

   hep-phInt.J.Mod.Phys.A(2018)·103 citations
6. 06*

   Resonant enhancement in leptogenesis

   P. S. Bhupal Dev🇺🇸 · Mathias Garny🇩🇪 · Juraj Klaric🇩🇪 · Peter Millington🇬🇧 · Daniele Teresi🇧🇪

   Vanilla leptogenesis within the type I seesaw framework requires the mass scale of the right-handed neutrinos to be above 10^9 GeV. This lower bound can be avoided if at least two of the sterile states are almost mass degenerate, which leads to an enhancement of the decay asymmetry. Leptogenesis models that can be tested in current and upcoming experiments often rely on this resonant enhancement, and a systematic and consistent description is therefore necessary for phenomenological applications. In this review article, we give an overview of different methods that have been used to study the saturation of the resonant enhancement when the mass difference becomes comparable to the characteristic width of the Majorana neutrinos. In this limit, coherent flavor transitions start to play a decisive role, and off-diagonal correlations in flavor space have to be taken into account. We compare various formalisms that have been used to describe the resonant regime and discuss under which circumstances the resonant enhancement can be captured by simplified expressions for the CP asymmetry. Finally, we briefly review some of the phenomenological aspects of resonant leptogenesis.

   hep-phInt.J.Mod.Phys.A(2018)·124 citations
7. 07*

   Status of rates and rate equations for thermal leptogenesis

   Simone Biondini🇨🇭 · Dietrich Bodeker🇩🇪 · Nora Brambilla🇩🇪 · Mathias Garny🇩🇪 · Jacopo Ghiglieri🇨🇭 · Andreas Hohenegger🇳🇴 · Mikko Laine🇨🇭 · Sebastian Mendizabal🇨🇱 · Peter Millington🇬🇧 · Alberto Salvio🇨🇭 · Antonio Vairo🇩🇪

   In many realizations of leptogenesis, heavy right-handed neutrinos play the main role in the generation of an imbalance between matter and antimatter in the early Universe. Hence, it is relevant to address quantitatively their dynamics in a hot and dense environment by taking into account the various thermal aspects of the problem at hand. The strong washout regime offers an interesting framework to carry out calculations systematically and reduce theoretical uncertainties. Indeed, any matter-antimatter asymmetry generated when the temperature of the hot plasma $T$ exceeds the right-handed neutrino mass scale $M$ is efficiently erased, and one can focus on the temperature window $T\ll M$. We review recent progresses in the thermal field theoretic derivation of the key ingredients for the leptogenesis mechanism: the right-handed neutrino production rate, the CP asymmetry in the heavy-neutrino decays and the washout rates. The derivation of evolution equations for the heavy-neutrino and lepton-asymmetry number densities, their rigorous formulation and applicability are also discussed.

   hep-phInt.J.Mod.Phys.A(2018)·62 citations
8. 08*

   Probing Leptogenesis

   E. J. Chun🇰🇷 · G. Cvetič🇨🇱 · P. S. B. Dev🇺🇸 · M. Drewes🇧🇪 · C. S. Fong🇧🇷 · B. Garbrecht🇩🇪 · T. Hambye🇧🇪 · J. Harz🇫🇷 · P. Hernández🇪🇸 · C. S. Kim🇰🇷 · E. Molinaro🇩🇰 · E. Nardi🇮🇹 and 3 other authors

   The focus of this chapter lies on the possible experimental tests of leptogenesis scenarios. We consider both leptogenesis generated from oscillations, as well as leptogenesis from out-of-equilibrium decays. As the Akhmedov-Rubakov-Smirnov (ARS) mechanism allows for heavy neutrinos in the GeV range, this opens up a plethora of possible experimental tests, e.g. at neutrino oscillation experiments, neutrinoless double beta decay, and direct searches for neutral heavy leptons at future facilities. In contrast, testing leptogenesis from out-of-equilibrium decays is a quite difficult task. We comment on the necessary conditions for having successful leptogenesis at the TeV-scale. We further discuss possible realizations and their model specific testability in extended seesaw models, models with extended gauge sectors, and supersymmetric leptogenesis. Not being able to test high-scale leptogenesis directly, we present a way to falsify such scenarios by focusing on their washout processes. This is discussed specifically for the left-right symmetric model and the observation of a heavy $W_R$, as well as model independently when measuring $\Delta L=2$ washout processes at the LHC or neutrinoless double beta decay.

   hep-phInt.J.Mod.Phys.A(2018)·117 citations
9. 09*

   CP Violation in the Lepton Sector and Implications for Leptogenesis

   C. Hagedorn🇩🇰 · R. N. Mohapatra🇺🇸 · E. Molinaro🇩🇰 · C. C. Nishi🇧🇷 · S. T. Petcov🇮🇹

   We review the current status of the data on neutrino masses and lepton mixing and the prospects for measuring the CP-violating phases in the lepton sector. The possible connection between low energy CP violation encoded in the Dirac and Majorana phases of the Pontecorvo-Maki-Nakagawa-Sakata mixing matrix and successful leptogenesis is emphasized in the context of seesaw extensions of the Standard Model with a flavor symmetry Gf (and CP symmetry).

   hep-phInt.J.Mod.Phys.A(2018)·54 citations
10. 10*

    The ILC Potential for Discovering New Particles

    Jenny List🇩🇪

    The LHC did not discover new particles beyond the Standard Model Higgs boson at 7 and 8 TeV, or in the first data samples at 13 TeV. However, the complementary nature of physics with $e^{+}{e}^{-}$ collisions still offers many interesting scenarios in which new particles can be discovered at the ILC. These scenarios take advantage of the capability of $e^{+}{e}^{-}$ collisions to observe particles with missing energy and small mass differences, to observe mono-photon events with precisely controlled backgrounds, and to observe the full range of exotic decay modes of the Higgs boson. The searches that an $e^{+}{e}^{-}$ collider makes possible are particularly important for models of dark matter involving a dark sector with particles above the modest energy reach of fixed-target experiments. In this talk, we will review the opportunities that the ILC offers for new particle discovery.

    hep-phhep-exPoS(2017)·1 citation
11. 11*

    The Physics Case for the $\sqrt{s_{NN}}\approx 10$ GeV Energy Region

    J. Cleymans🇿🇦

    There are indications that the beam energy region $\sqrt{s_{NN}}\approx 10$ GeV for heavy-ion collisions is an interesting one. The final state has the highest net baryon density at this beam energy. A transition from a baryon dominated to a meson dominated final state takes place around this beam energy. Ratios of strange particles to mesons show clear and pronounced maxima around this beam energy. The theoretical interpretation can be clarified by covering fully this energy region. In particular the strangeness content needs to be determined, data covering the full phase space ($4\pi$) would be helpful to establish the properties of this energy region.

    hep-phnucl-th6 citations
12. 12*

    Unparticle effects on $B\to D^{(\ast )}\tau \nu$

    Jong-Phil Lee🇰🇷

    We examine the possible unparticle effects on $R(D^{(\ast )})$ associated with $B\to D^{(\ast )}\tau \nu$ decays by minimum-${\chi }^2$ fitting. Recent measurements from Belle and LHCb are included in this analysis. While it is true that the new experimental results of $R(D^{(\ast )})$ get closer to the standard model predictions, there are still rooms for new physics and unparticles are also one possibility. Our best-fit values are $R(D)=0.456$ and $R(D^{\ast })=0.270$, which are still far from the standard model values by more than ($R(D)$) or almost ($R(D^{\ast })$) $2\sigma$. We also find that the unparticle effects are quite safe to render the branching ratio $\mathrm{Br}(B_c\to \tau \nu )$ less than 10\%.

    hep-phMod.Phys.Lett.A(2019)·3 citations
13. 13*

    Sivers and $\cos 2\varphi$ Asymmetries in Semi-inclusive Deep Inelastic Scattering in Light-front Holographic Model

    Tanmay Maji🇮🇳 · Dipankar Chakrabarti🇮🇳 · Asmita Mukherjee🇮🇳

    The spin asymmetries in SIDIS associated with $T$-odd TMDs are presented in a light-front quark-diquark model of a proton. To incorporate the effects of the final state interaction, the light front wave functions are modified to have a phase factor which is essential to have Sivers or Boer-Mulders functions. The Sivers and Boer-Mulder asymmetries are compared with HERMES and COMPASS data.

    hep-phPRD(2018)·20 citations
14. 14*

    Electroweak corrections to vector-boson scattering

    Benedikt Biedermann🇩🇪 · Ansgar Denner🇩🇪 · Mathieu Pellen🇩🇪

    We report on a recent calculation of the complete NLO QCD and electroweak corrections to the process $pp\to {\mu }^{+}{\nu }_{\mu }{e}^{+}{\nu }_{e}jj$, i.e. like-sign charged vector-boson scattering. The computation is based on the complete amplitudes involving two different orders of the strong and electroweak coupling constants at tree level and three different orders at one-loop level. We find electroweak corrections of $-13\%$ for the fiducial cross section that are an intrinsic feature of the vector-boson scattering process. For differential distributions, the corrections reach up to $-40\%$ in the phase-space regions explored. At the NLO level a unique separation between vector-boson scattering and irreducible background processes is not possible any more at the level of Feynman diagrams.

    hep-phhep-exPoS(2017)·0 citations
15. 15*

    Exclusive vector meson photoproduction with a leading baryon in photon - hadron interactions at hadronic colliders

    F. Carvalho🇧🇷 · V.P. Goncalves🇧🇷 · F.S. Navarra🇧🇷 · D. Spiering🇧🇷

    Exclusive vector meson photoproduction associated with a leading baryon ($B=n,{\Delta }^{+},{\Delta }^0$) in $pp$ and $pA$ collisions at RHIC and LHC energies is investigated using the color dipole formalism and taking into account nonlinear effects in the QCD dynamics. In particular, we compute the cross sections for $\rho$, $\varphi$ and $J/\Psi$ production together with a $\Delta$ and compare the predictions with those obtained for a leading neutron. Our results show that the $V+\Delta$ cross section is almost 30 % of the $V+n$ one. Our results also show that a future experimental analysis of these processes is, in principle, feasible and can be useful to study leading particle production.

    hep-phhep-exnucl-exnucl-thPRD(2018)·6 citations
16. 16*

    Transverse momentum spectra of hadrons in $p+p$ collisions at CERN SPS energies from the UrQMD transport model

    Vitalii Ozvenchuk🇵🇱 · Andrzej Rybicki🇵🇱

    The UrQMD transport model, version 3.4, is used to study the new experimental data on transverse momentum spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p$ and $\bar{p}$ produced in inelastic $p+p$ interactions at SPS energies, recently published by the NA61/SHINE Collaboration. The comparison of model predictions to these new measurements is presented as a function of collision energy for central and forward particle rapidity intervals. In addition, the inverse slope parameters characterizing the transverse momentum distributions are extracted from the predicted spectra and compared to the corresponding values obtained from NA61/SHINE distributions, as a function of particle rapidity and collision energy. A complex pattern of deviations between the experimental data and the UrQMD model emerges. For charged pions, the fair agreement visible at top SPS energies deteriorates with the decreasing energy. For charged $K$ mesons, UrQMD significantly underpredicts positive kaon production at lower beam momenta. It also underpredicts the central rapidity proton yield at top collision energy and overpredicts antiproton production at all considered energies. We conclude that the new experimental data analyzed in this paper still constitute a challenge for the present version of the model.

    hep-phnucl-thNPA(2018)·5 citations
17. 17*

    Energy peaks: a high energy physics outlook

    Roberto Franceschini🇮🇹

    Energy distributions of decay products carry information on the kinematics of the decay in ways that are at the same time straightforward and quite hidden. I will review these properties and discuss their early historical applications as well as more recent ones in the context of i) methods for the measurement of masses of new physics particle with semi-invisible decays, ii) the characterization of Dark Matter particles produced at colliders, iii) precision mass measurements of Standard Model particles, in particular of the top quark. Finally I will give an outlook of further developments and applications of energy peaks method for high energy physics at colliders and beyond.

    hep-phMod.Phys.Lett.A(2017)·1 citation
18. 18*

    Sub-MeV Self Interacting Dark Matter

    Bhavesh Chauhan🇮🇳

    In this paper, we present a model for sub-MeV dark matter with strong self interactions which can solve some of the small scale crisis of the $\Lambda$CDM. The dark matter is a Majorana fermion with only off-diagonal interactions with a hidden $U(1{)}_D$ gauge boson. The relic density is obtained by freeze-out of Boltzmann suppressed annihilations to a light fermionic species. The self interaction is a one loop process and constrained to be between 0.1 to 1 cm${}^2$/g. Severe constraints from the BBN on $N_{eff}$ require that the dark and visible sector are not in thermal equilibrium during freeze-out. The effect of this temperature asymmetry is studied.

    hep-phPRD(2018)·11 citations
19. 19*

    The effects of triplet Higgs bosons in long baseline neutrino experiments

    Katri Huitu🇫🇮 · Timo J. Kärkkäinen🇫🇮 · Jukka Maalampi🇫🇮 · Sampsa Vihonen🇫🇮

    The triplet scalars $(\Delta ={\Delta }^{++},{\Delta }^{+},{\Delta }^0)$, utilized in the so-called Type-II seesaw model to explain the lightness of neutrinos, would generate nonstandard interactions (NSI) for neutrino propagating in matter. We investigate the prospects to probe these interactions in long baseline neutrino oscillation experiments. We analyze the upper bounds that the proposed DUNE experiment might set on the nonstandard parameters and numerically derive upper bounds, as function of the lightest neutrino mass, on the ratio the mass $M_{\Delta }$ of the triplet scalars and strength $|{\lambda }_{\varphi }|$ of the coupling $\varphi \varphi \Delta$ of the triplet $\Delta$ and conventional Higgs doublet $\varphi$ . We also discuss the possible misinterpretation of these effects as effects arising from a nonunitarity of the neutrino mixing matrix and compare the results with the bounds that arise from the charged lepton flavor violating processes.

    hep-phPRD(2018)·7 citations
20. 20*

    Heavy quark complex potential in a strongly magnetized hot QGP medium

    Balbeer Singh🇮🇳 · Lata Thakur🇮🇳 · Hiranmaya Mishra🇮🇳

    We study the effect of a strong constant magnetic field, generated in relativistic heavy ion collisions, on the heavy quark complex potential. We work in the strong magnetic field limit with the lowest Landau level approximation. We find that the screening of the real part of the potential increases with the increase in the magnetic field. Therefore, we expect less binding of the $Q\bar{Q}$ pair in the presence of a strong magnetic field. The imaginary part of the potential increases in magnitude with the increase in the magnetic field, leading to an increase of the width of the quarkonium state with the magnetic field. All of these effects result in the early dissociation of $Q\bar{Q}$ states in a magnetized hot quark-gluon plasma medium.

    hep-phPRD(2018)·85 citations
21. 21*

    Non-minimal $331$ model for Lepton Flavour Universality Violation in $b\to s\ell \ell$ decays

    Sébastien Descotes-Genon🇫🇷 · Marta Moscati🇩🇪 · Giulia Ricciardi🇮🇹

    331 models constitute an extension of the Standard Model (SM) obtained by enlarging the SM gauge group $SU(3{)}_{\text{C}}\times SU(2{)}_{\text{L}}\times U(1{)}_Y$ to the group $SU(3{)}_{\text{C}}\times SU(3{)}_{\text{L}}\times U(1{)}_X$. We investigate how a non-minimal 331 model may embed lepton flavour universality violating contributions to $b\to s\ell \ell$ processes without introducing lepton flavour violation, as suggested by the recent LHCb measurements of the ratios $R_K$ and $R_{K^{\ast }}$. We discuss the model-independent scenarios of New Physics in $b\to s\ell \ell$ currently favoured by the data that could be accommodated by this model and consider a few phenomenological constraints on this model.

    hep-phPRD(2018)·32 citations
22. 22*

    Cosmic Archaeology with Gravitational Waves from Cosmic Strings

    Yanou Cui🇺🇸 · Marek Lewicki🇬🇧 · David E. Morrissey🇨🇦 · James D. Wells🇺🇸

    Cosmic strings are generic cosmological predictions of many extensions of the Standard Model of particle physics, such as a $U(1{)}^{\prime }$ symmetry breaking phase transition in the early universe or remnants of superstring theory. Unlike other topological defects, cosmic strings can reach a scaling regime that maintains a small fixed fraction of the total energy density of the universe from a very early epoch until today. If present, they will oscillate and generate gravitational waves with a frequency spectrum that imprints the dominant sources of total cosmic energy density throughout the history of the universe. We demonstrate that current and future gravitational wave detectors, such as LIGO and LISA, could be capable of measuring the frequency spectrum of gravitational waves from cosmic strings and discerning the energy composition of the universe at times well before primordial nucleosynthesis and the cosmic microwave background where standard cosmology has yet to be tested. This work establishes a benchmark case that gravitational waves may provide an unprecedented, powerful tool for probing the evolutionary history of the very early universe.

    hep-phastro-ph.COPRD(2018)·160 citations
23. 23*

    Probing the time structure of the quark-gluon plasma with top quarks

    Liliana Apolinário🇵🇹 · José Guilherme Milhano🇵🇹 · Gavin P. Salam🇨🇭 · Carlos A. Salgado🇪🇸

    The tiny droplets of Quark Gluon Plasma (QGP) created in high-energy nuclear collisions experience fast expansion and cooling with a lifetime of a few $\text{fm}/c$. Despite the information provided by probes such as jet quenching and quarkonium suppression, and the excellent description by hydrodynamical models, direct access to the time evolution of the system remains elusive. We point out that the study of hadronically-decaying $W$ bosons, notably in events with a top-antitop quark pair, can provide key novel insight, into the time structure of the QGP. This is because of a unique feature, namely a time delay between the moment of the collision and that when the $W$-boson decay products start interacting with the medium. Furthermore, the length of the time delay can be constrained by selecting specific reconstructed top-quark momenta.

    hep-phhep-exnucl-exnucl-thPRL(2018)·90 citations
24. 24*

    Heavy Higgs of the Twin Higgs Models

    Aqeel Ahmed🇩🇪

    Twin Higgs models are the prime illustration of neutral naturalness, where the new particles of the twin sector, gauge singlets of the Standard Model (SM), ameliorate the little hierarchy problem. In this work, we analyse phenomenological implications of the heavy Higgs of the Mirror Twin Higgs and Fraternal Twin Higgs models, when electroweak symmetry breaking is linearly realized. The most general structure of twin Higgs symmetry breaking, including explicit soft and hard breaking terms in the scalar potential, is employed. The direct and indirect searches at the LHC are used to probe the parameter space of Twin Higgs models through mixing of the heavy Higgs with the SM Higgs and decays of the heavy Higgs to the SM states. Moreover, for the Fraternal Twin Higgs, we study the production and decays of twin glueball and bottomonium states to the SM light fermions, which have interesting signatures involving displaced vertices and are potentially observable at the colliders.

    hep-phJHEP(2018)·43 citations
25. 25*

    Model independent analysis of semileptonic $B$ decays to $D^{\ast \ast }$ for arbitrary new physics

    Florian U. Bernlochner🇩🇪 · Zoltan Ligeti🇺🇸 · Dean J. Robinson🇺🇸

    We explore semileptonic $B$ decays to the four lightest excited charm mesons, $D^{\ast \ast }=\{D_0^{\ast },D_1^{\ast },$ $D_1,D_2^{\ast }\}$, for nonzero charged lepton mass and for all $b\to c\ell \bar{\nu }$ four-Fermi interactions, including calculation of the $\mathcal{O}({\Lambda }_{\text{QCD}}/m_{c,b})$ and $\mathcal{O}({\alpha }_s)$ corrections to the heavy quark limit for all form factors. In the heavy quark limit some form factors are suppressed at zero recoil, therefore, the $\mathcal{O}({\Lambda }_{\text{QCD}}/m_{c,b})$ corrections can be very important. The $D^{\ast \ast }$ rates exhibit sensitivities to new physics in $b\to c\tau \bar{\nu }$ mediated decays complementary to the $D$ and $D^{\ast }$ modes. Since they are also important backgrounds to $B\to D^{(\ast )}\tau \bar{\nu }$, the correct interpretation of future semitauonic $B\to D^{(\ast )}$ rate measurements requires consistent treatment of both the $D^{\ast \ast }$ backgrounds and the signals. Our results allow more precise and more reliable calculations of these $B\to D^{\ast \ast }\ell \bar{\nu }$ decays, and are systematically improvable by better data on the $e$ and $\mu$ modes. As an example, we show that the $D^{\ast \ast }$ rates are more sensitive to a new $\bar{c}{\sigma }_{\mu \nu }b$ tensor interaction than the $D^{(\ast )}$ rates.

    hep-phPRD(2018)·67 citations
26. 26*

    The balance of attractive and repulsive hadronic interactions: the influence of hadronic spectrum and excluded volume effects on lattice thermodynamics and consequences on experiments

    Paolo Alba

    Repulsive hadronic interactions play a relevant role in the QCD dynamics, attractive ones being represented by resonance formation. In this study we propose different schemes in order to parameterise repulsive interactions, then being able to extract effective sizes of hadrons from fits to lattice QCD simulations. We find that allowing a difference between the strange and light sectors, strange particles are systematically smaller than light ones with equal mass. The very simple implementation of repulsive interactions would in principle allow to extract precise information about all hadronic species once corresponding lattice observables, sensitive to the species of interest, are provided. With the parameterisation which best reproduces lattice data there is also a good description of experimental yields measured by ALICE and STAR experiments.

    ↳ nucl-thhep-lathep-phPRC(2019)·15 citations
27. 27*

    Possible origin of shoulder in the reactor antineutrino spectrum

    Ajit Kumar Mohanty🇮🇳

    The re-analysis of measured ${}^{238}U$ integrated electron spectrum reveals a shape mismatch with respect to the so called ab initio calculation and the ratio resembles well with the recently observed reactor antineutrino shoulder or bump around 5 MeV prompt energy when plotted in a reduced scale where the first two moments (area and average) of the spectrum are made identical (KNO type scaling). However, such bumps are not seen in case of other actinides like ${}^{235}U$ and ${}^{239,241}Pu$ isotopes. Since the magnitude of the bump in ${}^{238}U$ is comparable with the experimental observations, ${}^{238}U$ can not be the only source of anomaly unless similar contributions come from other uranium and plutonium isotopes as well. Therefore, it is strongly conjectured that the integrated electron spectra of uranium and plutonium isotopes particularly in the $6$ MeV to $8$ MeV energy range may have additional contributions coming from the harder part of the reactor neutron spectrum which may not be present in the thermal measurements.

    ↳ nucl-thhep-ph2 citations
28. 28*

    Chiral phase transition of three flavor QCD with nonzero magnetic field using standard staggered fermions

    Akio Tomiya🇨🇳 · Heng-Tong Ding🇨🇳 · Swagato Mukherjee🇺🇸 · Christian Schmidt🇩🇪 · Xiao-Dan Wang🇨🇳

    Lattice simulations for (2+1)-flavor QCD with external magnetic field demonstrated that the quark mass is one of the important parameters responsible for the (inverse) magnetic catalysis. We discuss the dependences of chiral condensates and susceptibilities, the Polyakov loop on the magnetic field and quark mass in three degenerate flavor QCD. The lattice simulations are performed using standard staggered fermions and the plaquette action with spatial sizes Ns = 16 and 24 and a fixed temporal size Nt = 4. The value of the quark masses are chosen such that the system undergoes a first order chiral phase transition and crossover with zero magnetic field. We find that in light mass regime, the quark chiral condensate undergoes magnetic catalysis in the whole temperature region and the phase transition tend to become stronger as the magnetic field increases. In crossover regime, deconfinement transition temperature is shifted by the magnetic field when quark mass ma is less than 0.4. The lattice cutoff effects are also discussed.

    ↳ hep-lathep-phnucl-thEPJ Web Conf.(2018)·8 citations
29. 29*

    Out-of-equilibrium chiral and $U_A(1)$ symmetry breaking in electromagnetic fields

    Xingyu Guo🇨🇳 · Pengfei Zhuang🇨🇳

    We systematically study quantum effect on chiral and $U_A(1)$ symmetry breaking under external electromagnetic fields in the frame of equal-time Wigner function formalism. We derive the transport and constraint equations for the quark distribution functions and the chiral and pion condensates in a Nambu--Jona-Lasinio model. By taking semi-classical expansion of the equations, chiral symmetry is broken at classical level, while $U_A(1)$ symmetry breaking happens only at quantum level. Beyond quasi-particle approximation, the quark off-shell effect leads to strong oscillation for the chiral and pion condensates.

    ↳ hep-thhep-phPRD(2018)·15 citations
30. 30*

    Quantum-gravity predictions for the fine-structure constant

    Astrid Eichhorn🇩🇪 · Aaron Held🇩🇪 · Christof Wetterich🇩🇪

    Asymptotically safe quantum fluctuations of gravity can uniquely determine the value of the gauge coupling for a large class of grand unified models. In turn, this makes the electromagnetic fine-structure constant calculable. The balance of gravity and matter fluctuations results in a fixed point for the running of the gauge coupling. It is approached as the momentum scale is lowered in the transplanckian regime, leading to a uniquely predicted value of the gauge coupling at the Planck scale. The precise value of the predicted fine-structure constant depends on the matter content of the grand unified model. It is proportional to the gravitational fluctuation effects for which computational uncertainties remain to be settled.

    ↳ hep-thgr-qchep-phPLB(2018)·71 citations
31. 31*

    High baryon and energy densities achievable in heavy-ion collisions at $\sqrt{s_{NN}}=$ 39 GeV

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Baryon and energy densities, which are reached in central Au+Au collisions at collision energy of $\sqrt{s_{NN}}=39$ GeV, are estimated within the model of three-fluid dynamics. It is shown that the initial thermalized mean proper baryon and energy densities in a sizable central region approximately are $n_B/n_0\approx$ 10 and $\epsilon \approx$ 40 GeV/fm${}^3$, respectively. The study indicates that the deconfinement transition at the stage of interpenetration of colliding nuclei makes the system quite opaque. The final fragmentation regions in these collisions are formed not only by primordial fragmentation fireballs, i.e. the baryon-rich matter passed through the interaction region (containing approximately 30\% of the total baryon charge), but also by the baryon-rich regions of the central fireball pushed out to peripheral rapidities by the subsequent almost one-dimensional expansion of the central fireball along the beam direction.

    ↳ nucl-thhep-exhep-phPRC(2018)·10 citations
32. 32*

    Bulk viscous corrections to screening and damping in the deconfined phase at high temperature

    Adrian Dumitru🇺🇸

    Non-equilibrium corrections in a hot QCD medium modify the "hard thermal loops" (HTL) which determine the resummed propagators for gluons with soft momenta as well as the Debye screening and Landau damping mass scales. We focus on bulk viscous corrections to a thermal fixed point. The screening and damping mass scales are sensitive to the bulk pressure and perhaps to (pseudo-) critical dynamical scaling of the bulk viscosity in the vicinity of a second-order critical point. This would affect the properties of quarkonium bound states in the deconfined phase.

    ↳ nucl-thhep-phPoS(2018)·0 citations
33. 33*

    Combination of KLOE $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma (\gamma ))$ measurements and determination of $a_{\mu }^{{\pi }^{+}{\pi }^{-}}$ in the energy range $0.10<s<0.95$ GeV${}^2$

    The KLOE-2 Collaboration: A. Anastasi · D. Babusci · M. Berlowski · C. Bloise · F. Bossi · P. Branchini · A. Budano · L. Caldeira Balkeståhl · B. Cao · F. Ceradini · P. Ciambrone · F. Curciarello and 52 other authors

    The three precision measurements of the cross section $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma (\gamma ))$ using initial state radiation by the KLOE collaboration provide an important input for the prediction of the hadronic contribution to the anomalous magnetic moment of the muon. These measurements are correlated for both statistical and systematic uncertainties and, therefore, the simultaneous use of these measurements requires covariance matrices that fully describe the correlations. We present the construction of these covariance matrices and use them to determine a combined KLOE measurement for $\sigma (e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\gamma (\gamma ))$. We find, from this combination, a two-pion contribution to the muon magnetic anomaly in the energy range $0.10<s<0.95$ GeV${}^2$ of $a_{\mu }^{{\pi }^{+}{\pi }^{-}}=(489.8\pm 1.7_{\mathrm{stat}}\pm 4.8_{\mathrm{sys}})\times 10^{-10}$.

    ↳ hep-exhep-phJHEP(2018)·190 citations
34. 34*

    Constraining a Thin Dark Matter Disk with Gaia

    Katelin Schutz🇺🇸 · Tongyan Lin🇺🇸 · Benjamin R. Safdi🇺🇸 · Chih-Liang Wu🇺🇸

    If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy that is coplanar with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including periodic comet impacts. Using the first data release from the $Gaia$ space observatory, we search for a dark disk via its effect on stellar kinematics in the Milky Way. Our new limits disfavor the presence of a thin dark matter disk, and we present updated measurements on the total matter density in the Solar neighborhood.

    ↳ astro-ph.GAhep-phPRL(2018)·104 citations
35. 35*

    Directed flow in heavy-ion collisions and its implications for astrophysics

    Yuri B. Ivanov🇷🇺

    Analysis of directed flow ($v_1$) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies $\sqrt{s_{NN}}$ = 2.7--39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. The crossover EoS is unambiguously preferable for the description of experimental data at lower collision energies $\sqrt{s_{NN}}\le$ 20 GeV. However, at higher collision energies $\sqrt{s_{NN}}\ge$ 20 GeV the purely hadronic EoS again becomes advantageous. This indicates that the deconfinement EoS in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. The latter finding is in agreement with that discussed in astrophysics in connection with existence of hybrid stars with masses up to about two solar masses.

    ↳ nucl-thastro-ph.HEhep-phnucl-exUniverse(2017)·6 citations
36. 36*

    Electromagnetic transition form factors of the Roper resonance in baryon chiral perturbation theory

    Mishiko Gelenava🇬🇪

    We consider the electromagnetic transition form factors of the Roper resonance in the framework of an effective field theory of pions, nucleons and delta and Roper resonances as explicit degrees of freedom. Due to the lack experimental data in the region of applicability of low energy effective field theory we fit available free coupling constants and compare obtained results compare to the predictions of a theoretical model.

    ↳ nucl-thhep-phEPJA(2018)·7 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.