Fri·Apr 27, 2018Friday·April 27, 2018

1. 01*

   Corrections of two-photon interactions in the fine and hyperfine structure of the P-energy levels of muonic hydrogen

   A.E. Dorokhov🇷🇺 · N.I. Kochelev🇨🇳 · A.P. Martynenko🇷🇺 · F.A. Martynenko🇷🇺 · A.E. Radzhabov🇨🇳

   In the framework of the quasipotential method in quantum electrodynamics we calculate corrections to the nuclear structure proportional to $r_N^2$ from two-photon exchange amplitudes in the fine and hyperfine structure of P-states in muonic hydrogen, as well as the photon-photon interaction amplitudes, leading to the exchange of the axial vector meson. In constructing the quasipotential of the muon-nucleus interaction, we use the method of projection operators on states of two particles with a definite spin and total angular momentum. Analytical calculation of the matrix elements is performed and contributions to the fine and hyperfine structure of the $2P_{1/2}$ and $2P_{3/2}$ levels are obtained.

   hep-phphysics.atom-phEPJA(2018)·17 citations
2. 02*

   Study on the PDF comparisons for quarkonium + $\gamma$ production at the LHC and FCC energies

   M.M. Machado🇧🇷 · G. Gil da Silveira🇧🇷

   The quarkonium plus photon production in coherent hadron-hadron interactions at the LHC is studied using the non-relativistic QCD factorization formalism. We investigate a set of kinematic distributions and compute the total cross sections for $J/\Psi +\gamma$ production. Our results demonstrate the feasibility of such process in the LHC kinematic regime and explore the possibilities for the Future Circular Collider, where higher event yields can be achieved.

   hep-ph0 citations
3. 03*

   Dimension-six electroweak top-loop effects in Higgs production and decay

   Eleni Vryonidou🇨🇭 · Cen Zhang🇨🇳

   We study the next-to-leading order electroweak corrections to Higgs processes from dimension-six top-quark operators in the Standard Model Effective Field Theory approach. We consider the major production channels, including $WH$, $ZH$, and VBF production at the LHC, and $ZH$, VBF production at future lepton colliders, as well as the major decay channels including $H\to \gamma \gamma ,\gamma Z,Wl\nu ,Zll,b\bar{b},\mu \mu ,\tau \tau$. The results show that within the current constraints, top-quark operators can shift the signal strength of the loop-induced processes, i.e. $H\to \gamma \gamma ,\gamma Z$, by factors of $\sim \mathcal{O}(1)-\mathcal{O}(10)$, and that of the tree-level processes, i.e. all remaining production and decay channels, by $\sim 5-10\%$ at the LHC, and up to $\sim 15\%$ at future lepton colliders. This implies that essentially all Higgs channels have started to become sensitive to top-quark couplings, and in particular, Higgs observables at high luminosity LHC as well as future lepton colliders, even below the $t\bar{t}$ threshold, will improve our knowledge of top-quark couplings. We derive the sensitivities of Higgs measurements to top-quark operators at the high luminosity LHC, using projections for both inclusive and differential measurements. We conclude that treating the dimension-six top-quark sector and the Higgs/electroweak sector separately may not continue to be a good strategy. A global analysis combining Higgs and top-quark measurements is desirable, and our calculation and implementation provide an automatic and realistic simulation tool for this purpose.

   hep-phhep-exJHEP(2018)·69 citations
4. 04*

   Long-Lived BLSSM Particles at the LHC

   W. Abdallah🇮🇳 · A. Hammad🇨🇭 · A. Kasem🇩🇪 · S. Khalil🇪🇬

   We investigate the collider signatures of neutral and charged Long-Lived Particles (LLPs), predicted by the Supersymmetric $B-L$ extension of the Standard Model (BLSSM), at the Large Hadron Collider (LHC). The BLSSM is a natural extension of the Minimal Supersymmetric Standard Model (MSSM) that can account for non-vanishing neutrino masses. We show that the lightest right-handed sneutrino can be the Lightest Supersymmetric Particle (LSP), while the Next-to-the LSP (NLSP) is either the lightest left-handed sneutrino or the left-handed stau, which are natural candidates for the LLPs. We analyze the displaced vertex signature of the neutral LLP (the lightest left-handed sneutrino), and the charged tracks associated with the charged LLP (the left-handed stau). We show that the production cross sections of our neutral and charged LLPs are relatively large, namely of order $\mathcal{O}(1)\mathrm{fb}$. Thus, probing these particles at the LHC is quite plausible. In addition, we find that the displaced di-lepton associated with the lightest left-handed sneutrino has a large impact parameter that discriminates it from other SM leptons. We also emphasize that the charged track associated with the left-handed stau has a large momentum with slow moving charged tracks, hence it is distinguished from the SM background and therefore it can be accessible at the LHC.

   hep-phPRD(2018)·11 citations
5. 05*

   Type II Seesaw with scalar dark matter in light of AMS-02, DAMPE and Fermi-LAT

   Tong Li🇦🇺 · Nobuchika Okada🇺🇸 · Qaisar Shafi🇺🇸

   The Standard Model (SM) supplemented by Type II Seesaw and a SM gauge-singlet scalar dark matter (DM) is a very simple framework to incorporate the observed neutrino oscillations and provide a plausible DM candidate. In this framework, the scalar DM naturally has a leptophilic nature with a pair annihilating mainly into the SM SU(2)${}_L$ triplet Higgs scalar of Type II Seesaw which, in turn, decay into leptons. In this work, we consider indirect signatures of this leptophilic DM and examine the spectrum of the cosmic ray electron/positron flux from DM pair annihilations in the Galactic halo. Given an astrophysical background spectrum of the cosmic ray electron/positron flux, we find that the contributions from DM annihilations can nicely fit the observed data from the AMS-02, DAMPE and Fermi-LAT collaborations, with a multi-TeV range of DM mass and a boost factor for the DM annihilation cross section of $\mathcal{O}(1000)$. The boost factor has a slight tension with the Fermi-LAT data for gamma-ray from dwarf spheroidal galaxies, which can be ameliorated with an enhanced local DM density by a factor of about 2.

   hep-phPRD(2018)·9 citations
6. 06*

   Heavy Mesons Photoproduction in Peripheral AA Collisions

   M. B. Gay Ducati🇧🇷 · S. Martins🇧🇷

   The exclusive photoproduction of the heavy vector mesons $\psi$'s and $Y$'s is investigated in peripheral lead-lead collisions for the energies available at the LHC, $\sqrt{s}=2.76$ TeV and $\sqrt{s}=5.02$ TeV. In order to evaluate the robustness of the light-cone color dipole formalism, previously tested in the ultraperipheral regime. It was calculated the rapidity distribution as well as the nuclear modification factor ($R_{AA}$) for the three centrality classes: 30%-50%, 50%-70% and 70%-90%. The transition from ultraperipheral to peripheral regime was carried out sophisticating the photon flux description and the photonuclear cross section, taking into account the effective interaction area. In our calculations, three scenarios were considered: (scenario 1) the direct application of the usual photon flux and of the photonuclear cross section without any relevant change in relation to the UPC's, (scenario 2) the application of an effective photon flux keeping the photonuclear cross section unchanged and (scenario 3) where it was also considered an effective photonuclear cross section. The results obtained from the three scenarios were compared with the ALICE measurements (only $J/\psi$ at the moment), showing a better agreement with the data in the more complete approach (scenario 3), mainly in the more central regions (30%-50% and 50%-70%) where the incertainty is smaller.

   hep-phPRD(2018)·32 citations
7. 07*

   $n$-$\bar{n}$ oscillations and the neutron lifetime

   George K. Leontaris🇬🇷 · John D. Vergados🇬🇷

   Neutron-antineutron oscillations are considered in the light of recently proposed particle models, which claim to resolve the neutron lifetime anomaly, indicating the existence of baryon violating $\Delta B=1$ interactions. Possible constraints are derived coming from the non-observation of neutron-antineutron oscillations, which can take place if the dark matter particle produced in neutron decay happens to be a Majorana fermion. It is shown that this can be realised in a simple MSSM extention where only the baryon number violating term $u^c{d}^c{d}^c$ is included whilst all other R-parity violating terms are prevented to avoid rapid proton decay. It is demostrated how this scenario can be implemented in a string motivated GUT broken to MSSM by fluxes.

   hep-phhep-exhep-thPRD(2019)·9 citations
8. 08*

   A first survey of the ghost-gluon vertex in the Gribov-Zwanziger framework

   B. W. Mintz🇧🇷 · L. F. Palhares🇧🇷 · S. P. Sorella🇧🇷 · A. D. Pereira🇩🇪

   As the restriction of the gauge fields to the Gribov region is taken into account, it turns out that the resulting gauge field propagators display a nontrivial infrared behavior, being very close to the ones observed in lattice gauge field theory simulations. In this work, we explore for the first time a higher correlation function in the presence of the Gribov horizon: the ghost-anti-ghost-gluon interaction vertex, at one-loop level. Our analytical results (within the so-called Refined Gribov Zwanziger theory) are fairly compatible with lattice YM simulations, as well as with solutions from the Schwinger-Dyson equations. This is an indication that the RGZ framework can provide a reasonable description in the infrared not only of gauge field propagators, but also of higher correlation functions, such as interaction vertices.

   hep-phhep-th1 citation
9. 09*

   Higgs boson $ZZ$ couplings in Higgs-strahlung at the ILC

   Taras V. Zagoskin🇺🇦 · Alexander Yu. Korchin🇺🇦

   We derive the fully differential cross section of the Higgs-strahlung process $f\bar{f}\to Z\to Z(\to f_Z{\bar{f}}_Z)X(\to f_X{\bar{f}}_X)$, where $f$, $f_Z$, and $f_X$ are arbitrary fermions and $X$ is a spin-zero particle with arbitrary couplings to $Z$ bosons and fermions. This process with $f=e$ and $X=h$ ($h$ denotes the Higgs boson) is planned to be measured at the ILC to put constraints on the couplings $g_1$, $g_2$, $g_3$ of the Higgs boson to $Z$ bosons. Using the obtained fully differential cross section, we define observables measurement of which yields the tightest constraints on the couplings. Explicit dependences of these observables on $g_i$ are derived.

   hep-phhep-exPRD(2018)·7 citations
10. 10*

    The automation of next-to-leading order electroweak calculations

    R. Frederix🇩🇪 · S. Frixione🇮🇹 · V. Hirschi🇨🇭 · D. Pagani🇩🇪 · H.-S. Shao🇫🇷 · M. Zaro🇳🇱

    We present the key features relevant to the automated computation of all the leading- and next-to-leading order contributions to short-distance cross sections in a mixed-coupling expansion, with special emphasis on the first subleading NLO term in the QCD+EW scenario, commonly referred to as NLO EW corrections. We discuss, in particular, the FKS subtraction in the context of a mixed-coupling expansion; the extension of the FKS subtraction to processes that include final-state tagged particles, defined by means of fragmentation functions; and some properties of the complex mass scheme. We combine the present paper with the release of a new version of MadGraph5_aMC@NLO, capable of dealing with mixed-coupling expansions. We use the code to obtain illustrative inclusive and differential results for the 13-TeV LHC.

    hep-phJHEP(2018)·561 citations
11. 11*

    The structure of generic anomalous dimensions and no-$\pi$ theorem for massless propagators

    P. A. Baikov🇷🇺 · K. G. Chetyrkin🇩🇪

    Extending an argument of [Baikov:2010hf] for the case of 5-loop massless propagators we prove a host of new exact model-independent relations between contributions proportional to odd and even zetas in generic \MSbar\ anomalous dimensions as well as in generic massless correlators. In particular, we find a new remarkable connection between coefficients in front of ${\zeta }_3$ and ${\zeta }_4$ in the 4-loop and 5-loop contributions to the QCD $\beta$-function respectively. It leads to a natural explanation of a simple mechanics behind mysterious cancellations of the $\pi$-dependent terms in one-scale Renormalization Group (RG) invariant Euclidian quantities recently discovered in \cite{Jamin:2017mul}. We give a proof of this no-$\pi$ theorem for a general case of (not necessarily scheme-independent) one-scale massless correlators. All $\pi$-dependent terms in the {\bf six-loop} coefficient of an anomalous dimension (or a $\beta$-function) are shown to be explicitly expressible in terms of lower order coefficients for a general one-charge theory. For the case of a scalar $O(n)$ ${\varphi }^4$ theory all our predictions for $\pi$-dependent terms in 6-loop anomalous dimensions are in full agreement with recent results of [Batkovich:2016jus],[Schnetz:2016fhy],[Kompaniets:2017yct].

    hep-phhep-thJHEP(2018)·40 citations
12. 12*

    CMB constraints on dark matter phenomenology via reheating in minimal plateau inflation

    Debaprasad Maity🇮🇳 · Pankaj Saha🇮🇳

    We consider the CMB constraints on reheating and dark matter parameter space for a specific plateau type inflationary model. The plateau inflationary models which are currently most favored models from data can be well approximated by a potential of the form $V(\varphi )\propto {\varphi }^n$ around $\varphi =0$. This fact makes it possible to study the reheating phase with general inflaton equation of state in a viable cosmological scenario. In addition, following our recent work[1], we generalize the connection between reheating and the present CMB data and the dark matter parameter space for general inflaton equation of state parameter.

    hep-phPhys.Dark Univ.(2019)·28 citations
13. 13*

    Evidence for maximality of strong interactions from LHC forward data

    E. Martynov🇺🇦 · B. Nicolescu🇷🇴

    It is important to check if the Froissaron-Maximal Odderon (FMO) approach is the only model in agreement with the LHC data. We therefore generalized the FMO approach by relaxing the ${\ln }^{2}s$ constraints both in the even-and odd-under-crossing amplitude. We show that, in spite of a considerable freedom of a large class of amplitudes, the best fits bring us back to the maximality of strong interaction. Moreover, if we leave Odderon Regge pole intercept ${\alpha }_O(0)$ completely free we find a very good solution for ${\alpha }_O(0)$ near -1 in agreement with the result of oddballs spectroscopy in QCD based on AdS/CFT correspondence.

    hep-phPLB(2018)·40 citations
14. 14*

    Higgs mode in $2+1$ dimensional $O(2)$ model

    Ji-Chong Yang🇨🇳 · Yu Shi🇨🇳

    We investigate the spectral functions of the Higgs mode in $O(2)$ model, which can be experimentally realized in a 2D Bose gas. Zero temperature limit is considered. Our calculation fully includes the 2-loop contributions. Peaks show up in the spectral functions of both the longitudinal and the scalar susceptibilities. Thus this model cannot explain the disappearance of the response at the weak interaction limit. Neither it can explain the similarity between the longitudinal and the scalar susceptibilities in the visibility of the Higgs mode. A possible lower peak at about $2m_{\sigma }$ is also noted.

    hep-phcond-mat.quant-gasInt.J.Mod.Phys.B(2021)·1 citation
15. 15*

    Searching for the QCD critical point via the rapidity dependence of cumulants

    Jasmine Brewer🇺🇸 · Swagato Mukherjee🇺🇸 · Krishna Rajagopal🇺🇸 · Yi Yin🇺🇸

    The search for a possible critical point in the QCD phase diagram is ongoing in heavy ion collision experiments at RHIC which scan the phase diagram by scanning the beam energy; a coming upgrade will increase the luminosity and extend the rapidity acceptance of the STAR detector. In fireballs produced in RHIC collisions, the baryon density depends on rapidity. By employing Ising universality together with a phenomenologically motivated freezeout prescription, we show that the resulting rapidity dependence of cumulant observables sensitive to critical fluctuations is distinctive. The dependence of the kurtosis (of the event-by-event distribution of the number of protons) on rapidity near mid-rapidity will change qualitatively if a critical point is passed in the scan. Hence, measuring the rapidity dependence of cumulant observables can enhance the prospect of discovering a critical point, in particular if it lies between two energies in the beam energy scan.

    hep-phnucl-exnucl-thPRC(2018)·57 citations
16. 16*

    Mirror Symmetry of quantum Yang-Mills vacua and cosmological implications

    Andrea Addazi🇨🇳 · Antonino Marcianò🇨🇳 · Roman Pasechnik🇸🇪 · George Prokhorov🇷🇺

    We find an argument related to the existence of a Z_2-symmetry for the renormalization group flow derived from the bare Yang-Mills Lagrangian, and show that the cancellation of the vacuum energy may arise motivated both from the renormalization group flow solutions and the effective Yang-Mills action. In the framework of the effective Savvidy's action, two Mirror minima are allowed, with exactly equal and hold opposite sign energy densities. At the cosmological level, we explore the stability of the electric and magnetic attractor solutions, both within and beyond the perturbation theory, and find that thanks to these latter the cancellation between the electric and the magnetic vacua components is achieved at macroscopic space and time separations. This implies the disappearance of the conformal anomaly in the classical limit of an effective Yang-Mills theory. In this picture, the tunneling probability from the Mirror vacua to the other vacua is exponentially suppressed in the quantum non-thermal state --- similarly to what happens for electroweak instantonic tunneling solutions. Specifically, we show that, in a dynamical Friedmann-Lemaître-Robertson-Walker (FLRW) cosmological background, the Nielsen-Olsen argument --- on the instability of uniform chromo-electric and chromo-magnetic Mirror vacua --- is subtly violated. The chromo-magnetic and chromo-electric uniform vacua are unstable only at asymptotic times, when the attractor to a zero energy density is already reached. The two vacua can safely decay into one anisotropic vacuum that has zero energy-density. We also discover a new surprising pattern of solitonic and anti-solitonic space-like solutions, which are sourced by the Yang-Mills dynamics in FLRW. We dub such non-perturbative configurations, which are directly related to dynamical cancellation mechanism of the vacuum energy, as {\it chronons}, or $\chi$-solutions.

    ↳ hep-thgr-qchep-phEPJC(2019)·14 citations
17. 17*

    Surface tension of quark droplets in compact stars and in the early universe

    A. G. Grunfeld🇦🇷 · G. Lugones🇧🇷

    We review the role of the surface tension of quark matter droplets in astrophysical conditions, focusing specifically on the thermodynamic conditions prevailing in cold neutron stars (NSs), in hot lepton rich proto NSs, and in early universe conditions. We analyze quark matter in chemical equilibrium under weak interactions, which is relevant for understanding the internal composition of hybrid stars, as well as just deconfined quark matter out of chemical equilibrium, which is the relevant thermodynamic state for describing the nucleation process of quark matter in NSs. We explore the role of temperature, density, trapped neutrinos, droplet size and magnetic fields within the multiple reflection expansion formalism (MRE). Quark matter is described within the frame of different effective models: the MIT bag model and the $SU(3{)}_f$ Nambu-Jona-Lasinio model (NJL), including color superconductivity, neutrino trapping and magnetic fields. We also analyze the deconfinement transition at vanishing chemical potential and finite temperature including the Polyakov loop. We explore some astrophysical consequences of our results.

    ↳ nucl-thhep-ph1 citation
18. 18*

    A comparison of the R_h=ct and LCDM cosmologies using the Cosmic Distance Duality Relation

    Fulvio Melia🇺🇸

    The cosmic distance duality (CDD) relation (based on the Etherington reciprocity theorem) plays a crucial role in a wide assortment of cosmological measurements. Attempts at confirming it observationally have met with mixed results, though the general consensus appears to be that the data do support its existence in nature. A common limitation with past approaches has been their reliance on a specific cosmological model, or on measurements of the luminosity distance to Type Ia SNe, which introduces a dependence on the presumed cosmology in spite of beliefs to the contrary. Confirming that the CDD is actually realized in nature is crucial because its violation would require exotic new physics. In this paper, we study the CDD using the observed angular size of compact quasar cores and a Gaussian Process reconstruction of the HII galaxy Hubble diagram---without pre-assuming any particular background cosmology. In so doing, we confirm at a very high level of confidence that the angular-diameter and luminosity distances do indeed satisfy the CDD. We then demonstrate the potential power of this result by utilizing it in a comparative test of two competing cosmological models---the R_h=ct universe and LCDM---and show that R_h=ct is favoured by the CDD data with a likelihood ~82.3% compared with ~17.7% for the standard model.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phMNRAS(2018)·44 citations
19. 19*

    On the Universality of the Chern-Simons Diffusion Rate

    Francesco Bigazzi🇮🇹 · Aldo L. Cotrone🇮🇹 · Flavio Porri🇮🇹

    We prove the universality of the Chern-Simons diffusion rate - a crucial observable for the chiral magnetic effect - in a large class of planar strongly correlated gauge theories with dual string description. When the effects of anomalies are suppressed, the diffusion rate is simply given in terms of temperature, entropy density and gauge coupling, with a universal numerical coefficient. We show that this result holds, in fact, for all the top-down holographic models where the calculation has been performed in the past, even in presence of magnetic fields and anisotropy. We also extend the check to further well known models for which the same computation was lacking. Finally we point out some subtleties related to the definition of the Chern-Simons diffusion rate in the presence of anomalies. In this case, the usual definition of the rate - a late time limit of the imaginary part of the retarded correlator of the topological charge density - would give an exactly vanishing result, due to its relation with a non-conserved charge correlator. We confirm this observation by explicit holographic computations on generic isotropic black hole backgrounds. Nevertheless, a non-trivial Chern-Simons relaxation time can in principle be extracted from a quasi-normal mode calculation.

    ↳ hep-thhep-phPRD(2018)·8 citations
20. 20*

    Probing Decoupling in Dark Sectors with the Cosmic Microwave Background

    Gongjun Choi🇺🇸 · Chi-Ting Chiang🇺🇸 · Marilena LoVerde🇺🇸

    The acoustic peaks in the angular power spectrum of cosmic microwave background (CMB) temperature and polarization anisotropies play an important role as a probe of the nature of new relativistic particles contributing to the radiation density in the early universe, parametrized by $\Delta N_{eff}$. The amplitude and phase of the acoustic oscillations provide information about whether the extra species are free-streaming particles, like neutrinos, or tightly-coupled, like the photons, during eras probed by the CMB. On the other hand, some extensions of the Standard Model produce new relativistic particles that decouple from their own non-gravitational interactions after neutrinos, but prior to photons. We study the signature of new relativistic species that decouple during this intermediate epoch. We argue that the decoupling species will cause a scale-dependent change in the amplitude and phase shift of the acoustic oscillations, different from the usual constant shifts on small scales. For intermediate decoupling times, the phase and amplitude shifts depend not only on $\Delta N_{eff}$ but the redshift $z_{dec,X}$ at which the new species decoupled. For $\Delta N_{eff}>0.334$, a Stage IV CMB experiment could determine $N_{eff}$ at the percent level and $z_{dec,X}$ at the $\sim 10\%$ level. For smaller values, $\Delta N_{eff}\sim 0.1$, constraints on $z_{dec,X}$ weaken but remain $\sim 20-50\%$ for $z_{dec,X}\sim \mathcal{O}(10^3-10^4)$. As an application, we study the contributions to $\Delta N_{eff}$ and determine the $z_{dec,X}$ values for simple implementations of the so-called $N$naturalness model.

    ↳ astro-ph.COhep-phJCAP(2018)·52 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.