HEP Phenomenology·hep-ph

Tue·Jul 3, 2018Tuesday·July 3, 2018

46 papers—27 primary·19 cross-listed·reconstructed*

01*
Mu-tau symmetry and the Littlest Seesaw
Stephen F. King🇬🇧 · Celso C. Nishi🇧🇷
Motivated by the latest neutrino oscillation data which is consistent with maximal atmospheric mixing and maximal leptonic CP violation, we review various results in $μτ$ symmetry, then include several new observations and clarifications, including identifying a new general form of neutrino mass matrix with $μτ$ symmetry. We then apply the new results to the neutrino mass matrix associated with the Littlest Seesaw model, and show that it approximately satisfies the new general form with $μτ$ symmetry, and that this is responsible for its approximate predictions of maximal atmospheric mixing and maximal CP violation in the lepton sector.
hep-phPLB(2018)·36 citations
02*
Beyond the Standard Model' 17
Dmitry Kazakov🇷🇺
We discuss the status of the SM - The principles - The Lagrangian - The problems - Open questions - The ways beyond. Then we consider possible physics beyond the SM - New symmetries (Gauge, SUSY, etc) - New particles (gauge, axion, superpartners) - New dimensions (extra, large, compact, etc) - New Paradigm (strings, branes, gravity). In conclusion, we formulate the first priority tasks for the future HEP program.
hep-phCERN Yellow Rep.School Proc.(2018)·4 citations
03*
Exotics at Our Home
Nikolay Achasov🇷🇺
I. Light Scalars as Four-quark States II. Isotensor Tensor Tensor E(1500-1600) State III. X(3872) State as Charmonium \chi_{c1}(2P) IV. Two-gluon Annihilation of Charmonium \chi_{c2}(2P) There are considered problems of the exotic states, in which the author with his collaborators has made clear physical predictions, considerable part of wich is supported by experement already
hep-phhep-exnucl-exEPJ Web Conf.(2018)·1 citation
04*
Model-independent sensibility studies for the anomalous dipole moments of the $ν_{τ}$ at the CLIC based $γ e^{-}$ colliders
A. A. Billur🇹🇷 · M. Koksal🇹🇷 · A. Gutierrez-Rodriguez🇲🇽 · M. A. Hernandez-Ruiz🇲🇽
To improve the theoretical prediction of the anomalous dipole moments of the $τ$ -neutrino, we have carried out a study through the process $γ e^{-} \to τ ν ˉ_{τ} ν_{e}$ , which represents an excellent and useful option in determination of these anomalous parameters. To study the potential of the process $γ e^{-} \to τ ν ˉ_{τ} ν_{e}$ , we apply a future high-energy and high-luminosity linear electron-positron collider, such as the CLIC, with $s = 380, 1500, 3000 G e V$ and $L = 10, 50, 100, 200, 500, 1000, 1500, 2000, 3000 f b^{- 1}$ , and we consider systematic uncertainties of $δ_{sy s} = 0, 5, 10%$ . With these elements, we present a comprehensive and detailed sensitivity study on the total cross-section of the process $γ e^{-} \to τ ν ˉ_{τ} ν_{e}$ , as well as on the dipole moments $μ_{ν_{τ}}$ and $d_{ν_{τ}}$ at the $95%$ C.L., showing the feasibility of such process at the CLIC at the $γ e^{-}$ mode with unpolarized and polarized electron beams.
hep-phPRD(2018)·10 citations
05*
Tests of the Standard Model in $B \to D ℓ ν_{ℓ}$ , $B \to D^{*} ℓ ν_{ℓ}$ and $B_{c} \to J / ψ ℓ ν_{ℓ}$
Thomas D. Cohen🇺🇸 · Henry Lamm🇺🇸 · Richard F. Lebed🇺🇸
A number of recent experimental measurements suggest the possibility of a breakdown of lepton ( $ℓ$ ) universality in exclusive $b \to c ℓ ν_{ℓ}$ semileptonic meson decays. We analyze the full differential decay rates for several such processes, and show how to extract combinations of the underlying helicity amplitudes that are completely independent of $m_{ℓ}$ . Ratios of these combinations for different $ℓ$ (as well as some combinations for a single value of $ℓ$ ) therefore equal unity in the Standard Model and provide stringent tests of lepton universality. Furthermore, the extractions assume the form of weighted integrals over the differential decay rates and therefore are useful even in situations where data in some regions of allowed phase space may be sparse.
hep-phhep-exPRD(2018)·20 citations
06*
Probing the Higgs Yukawa coupling to the top-quark at the LHC via single top + Higgs production
Vernon Barger🇺🇸 · Kaoru Hagiwara🇯🇵 · Ya-Juan Zheng🇯🇵
The conjoined production at the LHC of single top and Higgs boson via $t$ -channel weak boson exchange is ideal to probe the top-quark Yukawa coupling, due to a delicate cancellation between the amplitudes with the $h tt$ and the $hW W$ couplings. We find that the top quark is produced with $100%$ polarization in the leading order, and its quantum state is determined by the spin-vector direction in the $t$ -quark rest frame. We relate the spin direction to the four-momenta of the top, Higgs and a jet in the helicity amplitude framework. We identify a polarization asymmetry that is sensitive to CP violation, even after partial integration over the forward jet momentum. This CP violating asymmetry may be observed at the LHC via the component of the top-quark polarization that is perpendicular to the $t h$ scattering plane.
hep-phPRD(2019)·15 citations
07*
Probing the seesaw scale with gravitational waves
Nobuchika Okada🇺🇸 · Osamu Seto🇯🇵
The $U (1)_{B - L}$ gauge symmetry is a promising extension of the standard model of particle physics, which is supposed to be broken at some high energy scale. Associated with the $U (1)_{B - L}$ gauge symmetry breaking, right-handed neutrinos acquire their Majorana masses and then tiny light neutrino masses are generated through the seesaw mechanism. In this paper, we demonstrate that the first-order phase transition of the $U (1)_{B - L}$ gauge symmetry breaking can generate a large amplitude of stochastic gravitational wave (GW) radiation for some parameter space of the model, which is detectable in future experiments. Therefore, the detection of GWs is an interesting strategy to probe the seesaw scale which can be much higher than the energy scale of collider experiments.
hep-phastro-ph.COPRD(2018)·72 citations
08*
The effect of the scalar unparticle on the production of Higgs - radion at high energy colliders
D. V. Soa🇻🇳 · B. T. H. Giang🇻🇳
An attempt is made to present the influence of the scalar unparticle on some scattering processes in the Randall - Sundum model. The contribution of the scalar unparticle on the production of Higgs - radion at high energy colliders is studied in detail. We evaluate the production cross-sections in the electron-positron ( $e^{+} e^{-}$ ), photon-photon ( $γ γ$ ) and gluon-gluon ( $g g$ ) collisions, which depend strongly on the collision energy $s$ , the scaling dimension $d_{U}$ of the unparticle operator $O_{U}$ and the energy scale $Λ_{U}$ . Numerical evaluation shows that the cross - sections for the pair production of scalar particles are much larger than that of the associated production of the scalar particle with unparticle in the same condition
hep-phNPB(2018)·9 citations
09*
Effects of quantum statistics on relic density of Dark Radiation
Marek Olechowski🇵🇱 · Paweł Szczerbiak🇵🇱
The freeze-out of massless particles is investigated. The effects due to quantum statistics, Fermi-Dirac or Bose-Einstein, of all particles relevant for the process are analyzed. Solutions of appropriate Boltzmann equation are compared with those obtained using some popular approximate methods. As an application of general results the relic density of dark radiation in Weinberg's Higgs portal model is discussed.
hep-phEPJC(2018)·6 citations
10*
Peaks and cusps: anomalous thresholds and LHC physics
Giampiero Passarino (Turin U. & INFN, Turin)🇮🇹
The behavior of scattering amplitudes in the vicinity of a physical-region Landau singularity is considered. The impact on LHC processes is discussed.
hep-phhep-th17 citations
11*
Resumming subleading Sudakov logarithms in saturation regime
Jian Zhou🇨🇳
We investigate the scale dependence of transverse momentum dependent(TMD) gluon distribution in saturation regime. We found that in the Collins-2011 scheme, the scale dependence of small x gluon TMD is governed by the same renormalization group(RG) equation that holds at moderate or large $x$ . Following the standard procedure, one then can resum both double leading logarithm and single leading logarithm in saturation regime by jointly solving the Collins-Soper equation and the RG equation.
hep-phPRD(2019)·29 citations
12*
Light Dark Matter Showering under Broken Dark $U (1)$ -- Revisited
Junmou Chen🇰🇷 · Pyungwon Ko🇰🇷 · Hsiang-nan Li🇹🇼 · Jinmian Li🇰🇷 · Hiroshi Yokoya🇰🇷
It was proposed recently that different chiralities of the dark matter (DM) fermion under a broken dark U(1) gauge group can lead to distinguishable signatures at the LHC through shower patterns, which may reveal the mass origin of the dark sector. We study this subject further by examining the dark shower of two simplified models, the dubbed Chiral Model and the Vector Model. We derive a more complete set of collinear splitting functions with power corrections, specifying the helicities of the initial DM fermion and including the contribution from an extra degree of freedom, the dark Higgs boson. The dark shower is then implemented with these splitting functions, and the new features resulting from its correct modelling are emphasized. It is shown that the DM fermion chirality can be differentiated by measuring dark shower patterns, especially the DM jet energy profile, which is almost independent of the DM energy.
hep-phhep-exJHEP(2019)·11 citations
13*
Dark Matter Casts Light on the Early Universe
A. Arbey🇫🇷 · J. Ellis🇬🇧 · F. Mahmoudi🇫🇷 · G. Robbins🇫🇷
We show how knowledge of the cold dark matter (CDM) density can be used, in conjunction with measurements of the parameters of a scenario for beyond the Standard Model (BSM) physics, to provide information about the evolution of the Universe before Big Bang Nucleosynthesis (BBN). As examples of non-standard evolution, we consider models with a scalar field that may decay into BSM particles, and quintessence models. We illustrate our calculations using various supersymmetric models as representatives of classes of BSM scenarios in which the CDM density is either larger or smaller than the observed density when the early Universe is assumed to be radiation-dominated. In the case of a decaying scalar field, we show how the CDM density can constrain the initial scalar density and the reheating temperature after it decays in BSM scenarios that would yield overdense dark matter in standard radiation-dominated cosmology, and how the decays of the scalar field into BSM particles can be constrained in scenarios that would otherwise yield underdense CDM. We also show how the early evolution of the quintessence field can be constrained in BSM scenarios.
hep-phastro-ph.COJHEP(2018)·29 citations
14*
Muon g-2 and rare top decays in up-type specific variant axion models
Cheng-Wei Chiang🇹🇼 · Michihisa Takeuchi🇯🇵 · Po-Yan Tseng🇯🇵 · Tsutomu T. Yanagida🇯🇵
The invisible variant axion models (VAM's) offer a very attractive solution for the strong CP problem without the domain wall problem. We consider the up-type specific variant axion models and examine their compatibility with the muon $g - 2$ anomaly and the constraints from lepton flavor universality, several flavor observables, and top quark measurements. We find that the combined $χ^{2}$ fit favors the parameters $m_{A} \sim 15$ GeV and $tan β \sim 40$ , the same as the type-X 2HDM. Moreover, we find that there are no conflict with any flavor observables as long as the mixing angle $ρ_{u}$ is sufficiently small. In particular, a small nonzero mixing angle $ρ_{u} \sim π /100$ is slightly favored by the observed $B_{s} \to μμ$ branching ratio. The up-specific VAM predicts the flavor-violating top rare decay $t \to u A$ followed by $A \to τ τ$ , which would provide a smoking gun signature at the LHC. We show that current searches of $A$ already impose some constraints on the parameter space but are not sensitive to the most interesting light $m_{A}$ region. We propose an efficient search strategy that employs di-tau tagging using jet substructure information, and demonstrate that it can enhance the sensitivity on $B R (t \to u A)$ , especially in the light $m_{A}$ region. This model also predicts the flavor-violating decay of heavy Higgs bosons, such as $H \to t u$ , that would suppress the $H \to τ τ / μμ$ decays. We also examine the up-specific VAM with the muon-specific lepton sector and the down-type specific VAM's as interesting alternative scenarios.
hep-phhep-exPRD(2018)·11 citations
15*
A glimpse of heavy scales through the electroweak resonance theory
Joaquín Santos🇪🇸
The apparent absence of new heavy states at the LHC below the TeV scale points that there is a gap in the electroweak energy spectrum. This scenario is conveniently described through the electroweak effective theory, an effective description that contains the Standard Model fields and symmetries. A generic non-linear realization of the electroweak symmetry breaking pattern $S U (2)_{L} \otimes S U (2)_{R} \to S U (2)_{L + R}$ with a singlet Higgs is adopted, with no assumption about how it couples to the Standard Model. To seek for heavy particles, we formulate the electroweak resonance theory as the most general high-energy Lagrangian including both fermionic and $J^{P} = 0^{\pm}, 1^{\pm}$ bosonic heavy states, where all the resonances can form n-plets under the electroweak and the color group. An extended analysis of the imprints that the heavy states leave on the low-energy theory is performed, with an special emphasis on spin-1 fields and their formalism implementation. We study the phenomenology of the $P$ even purely bosonic sector of the resonance theory, where the low-energy predictions are refined with the assumption of very reasonable ultraviolet constraints.
hep-ph0 citations
16*
Anatomy of $B_{s} \to V V$ decays and effects of next-to-leading order contributions in the perturbative QCD factorization approach
Da-Cheng Yan🇨🇳 · Xin Liu🇨🇳 · Zhen-Jun Xiao🇨🇳
By employing the perturbative QCD (PQCD) factorization approach, we calculated the branching ratios, CP-violating asymmetries, the longitudinal and transverse polarization fractions and other physical observables of the thirteen charmless hadronic $B ˉ_{s}^{0} \to V V$ decays with the inclusion of all currently known next-to-leading order (NLO) contributions. We focused on the examination of the effects of all those currently known NLO contributions and found that: (a) for the measured decays $B ˉ_{s}^{0} \to ϕϕ, K^{* 0} ϕ, K ˉ^{* 0} K^{* 0}$ and $ρ^{0} ϕ$ , the NLO contributions can provide $\sim 20%$ to $\sim 40%$ enhancements to the leading order (LO) PQCD predictions of their CP-averaged branching ratios, and consequently the agreement between the PQCD predictions and the measured values are improved effectively after the inclusion of the NLO contributions; (b) for the measured decays, the NLO corrections to the LO PQCD predictions for $(f_{L}, f_{⊥})$ and $(ϕ_{∥}, ϕ_{⊥})$ are generally small in size, but the weak penguin annihilation contributions play an important role in understanding the data about their decay rates, $f_{L}$ and $f_{⊥}$ ; (c) the NLO PQCD predictions for above mentioned physical observables do agree with the measured ones and the theoretical predictions from the QCDF, SCET and FAT approaches; (d) for other considered $B_{s}^{0} \to V V$ decays, the NLO PQCD predictions for their decay rates and other physical observables are also basically consistent with the theoretical predictions from other popular approaches, future precision measurements could help us to test or examine these predictions.
hep-phhep-exNPB(2018)·34 citations
17*
W polarization in $e^{+} e^{-}$ , gluon-gluon and $γ γ \to W t b ˉ$ for testing the top quark mass structure and the presence of final interactions
Fernand M Renard🇫🇷
We analyze the $W t b ˉ$ production processes and especially the rate of longitudinal $W$ polarization sensitive to a possible top quark mass scale dependence and to the presence of strong final state $W t$ interactions for example generated by a dark matter environment. We give illustrations for the three processes $e^{+} e^{-}$ , gluon-gluon and $γ γ \to W t b ˉ$ .
hep-ph8 citations
18*
Indirect search for color octet electron at PWFA-LC
A. N. Akay🇹🇷 · U. Kaya🇹🇷 · S. Turkoz🇹🇷
Indirect search for color octet electron at Plasma Wake Field Accelerator- Linear Collider (PWFA-LC) has been considered. It is shown that color octet electron masses can be probed up to 17.7 TeV at PWFA-LC with three years integrated luminosity. In addition, the compositeness scale can be probed up to 38.5 TeV.
hep-phhep-ex0 citations
19*
Systematic classification of three-loop realizations of the Weinberg operator
Ricardo Cepedello🇪🇸 · Renato M. Fonseca🇨🇿 · Martin Hirsch🇪🇸
We study systematically the decomposition of the Weinberg operator at three-loop order. There are more than four thousand connected topologies. However, the vast majority of these are infinite corrections to lower order neutrino mass diagrams and only a very small percentage yields models for which the three-loop diagrams are the leading order contribution to the neutrino mass matrix. We identify 73 topologies that can lead to genuine three-loop models with fermions and scalars, i.e. models for which lower order diagrams are automatically absent without the need to invoke additional symmetries. The 73 genuine topologies can be divided into two sub-classes: Normal genuine ones (44 cases) and special genuine topologies (29 cases). The latter are a special class of topologies, which can lead to genuine diagrams only for very specific choices of fields. The genuine topologies generate 374 diagrams in the weak basis, which can be reduced to only 30 distinct diagrams in the mass eigenstate basis. We also discuss how all the mass eigenstate diagrams can be described in terms of only five master integrals. We present some concrete models and for two of them we give numerical estimates for the typical size of neutrino masses they generate. Our results can be readily applied to construct other $d = 5$ neutrino mass models with three loops.
hep-phJHEP(2018)·53 citations
20*
Exploring the Quark-Gluon Vertex with Slavnov-Taylor Identities and Lattice Simulations
Orlando Oliveira🇵🇹 · T. Frederico🇧🇷 · W. de Paula🇧🇷 · J. P. B. C de Melo🇧🇷
The soft gluon limit of the longitudinal part of the quark-gluon vertex is studied by resorting to non-perturbative approaches to Quantum Chromodynamics (QCD). Based on a Slavnov-Taylor identity (STI), the longitudinal form factors is expressed in terms of the quark-ghost kernel, the quark self energy and the quark wave function. An exact relation between the non-vanishing longitudinal form factors is derived for the soft gluon limit and explored to understand the behaviour of the vertex. Within a Ball-Chiu vertex, the form factor $λ_{1}$ was analysed using recent lattice simulations for full QCD for the soft gluon limit. The lattice data shows that the gluon propagator resumes the momentum dependence of such component of the vertex. This connection is understood via a fully dressed one-loop Bethe-Salpeter equation. The behaviour of the remaining longitudinal form factors $λ_{2} (p^{2})$ and $λ_{3} (p^{2})$ is investigated combining both the information of lattice simulations and the derived relations based on the STI.
hep-phhep-lathep-thEPJC(2018)·38 citations
21*
The $Ω (2012)$ as a hadronic molecule
M. Pavon Valderrama🇨🇳
Recently the Belle collaboration has discovered a narrow $S = - 3$ baryon, the $Ω (2012)$ . We explore the possibility that the $Ω (2012)$ is a $Ξ (1530) K ˉ$ molecule, where the binding mechanism is the coupled channel dynamics with the $Ω η$ channel. The characteristic signature of a molecular $Ω (2012)$ will be its decay into the three body channel $Ξ π K ˉ$ , for which we expect a partial decay width of $2 - 3 MeV$ . The partial decay width into the $Ξ K ˉ$ channel should lie in the range of $1 - 11 MeV$ , a figure compatible with experiment and which we have deduced from the assumption that the coupling involved in this decay is of natural size. For comparison purposes the decay of a purely compact $Ω (2012)$ into the $Ξ K ˉ$ and $Ξ π K ˉ$ channels is of the same order of magnitude as and one order of magnitude smaller than in the molecular scenario, respectively. This comparison indicates that the current experimental information is insufficient to distinguish between a compact and a molecular $Ω (2012)$ and further experiments will be required to determine its nature. A molecular $Ω (2012)$ will also imply the existence of two- and three-body molecular partners. The two-body partners comprise two $Λ$ hyperons located at $1740$ and $1950 MeV$ respectively, the first of which might correspond to the $Λ (1800)$ while the second to the $Λ (2000)$ or the $Λ (2050)$ . The three-body partners include a $Ξ (1530) K K ˉ$ and a $Ξ (1530) η K ˉ$ molecule, with masses of $M = 2385 - 2445 MeV$ and $M = 2434 - 2503 MeV$ respectively. We might be tempted to identify the first with the $Ξ (2370)$ and the latter with the $Ω (2470)$ listed in the PDG.
hep-phhep-exhep-latnucl-thPRD(2018)·55 citations
22*
Renormalization of the multi-Higgs-doublet Standard Model and one-loop lepton mass corrections
Walter Grimus🇦🇹 · Maximilian Löschner🇦🇹
Motivated by models for neutrino masses and lepton mixing, we consider the renormalization of the lepton sector of a general multi-Higgs-doublet Standard Model with an arbitrary number of right-handed neutrino singlets. We propose to make the theory finite by $\mbox M S$ renormalization of the parameters of the unbroken theory. However, using a general $R_{ξ}$ gauge, in the explicit one-loop computations of one-point and two-point functions it becomes clear that---in addition---a renormalization of the vacuum expectation values (VEVs) is necessary. Moreover, in order to ensure vanishing one-point functions of the physical scalar mass eigenfields, finite shifts of the tree-level VEVs, induced by the finite parts of the tadpole diagrams, are required. As a consequence of our renormalization scheme, physical masses are functions of the renormalized parameters and VEVs and thus derived quantities. Applying our scheme to one-loop corrections of lepton masses, we perform a thorough discussion of finiteness and $ξ$ -independence. In the latter context, the tadpole contributions figure prominently.
hep-phJHEP(2018)·20 citations
23*
The KSVZ Axion Model with Quasi-Degenerate Minima: A Unified Model for Dark Matter and Dark Energy
Amy Lloyd-Stubbs🇬🇧 · John McDonald🇬🇧
We consider the possibility that dark matter and dark energy can be explained by the minimal KSVZ axion model. This is possible if the lowest energy metastable minimum of the scalar potential has zero energy density, which is possible in theoretical models of vacuum energy cancellation based on spacetime averaging and in models based on energy parity. Dark energy is then understood as being due to the energy density of the metastable electroweak vacuum relative to a second quasi-degenerate metastable minimum. The requirement of quasi-degenerate minima is a non-trivial condition which completely determines the form of the potential for a given value of the axion decay constant, $f_{a}$ , and the PQ scalar self-coupling, $λ_{ϕ}$ . The existence of the second quasi-degenerate minimum imposes a new lower bound on the axion decay constant, $f_{a} \geq 2.39 \times 1 0^{10} λ_{ϕ}^{- 1/4}$ GeV. If the PQ symmetry is broken after inflation then the lower bound on $f_{a}$ implies a lower bound on the amount of axion dark matter, $Ω_{a} / Ω_{d m} \geq (0.28 - 0.46) λ_{ϕ}^{- 0.291}$ , where the range is due to the uncertainty in the amount of axion dark matter produced by vacuum realignment, cosmic strings and domain walls, therefore at least 30 $%$ of dark matter must be due to axions if $λ_{ϕ} ≲ 1$ . When axions constitute all of the dark matter and the PQ symmetry is broken after inflation, $f_{a}$ , and so the form of the scalar potential, is completely fixed for a given value of $λ_{ϕ}$ , with only a weak dependence on $λ_{ϕ}$ . This will allow the inflation and post-inflation evolution of the model to be quantitatively studied for a given inflation model and dimensionally natural values of $λ_{ϕ}$ .
hep-phastro-ph.COPRD(2019)·6 citations
24*
Systematics of azimuthal anisotropy harmonics in proton-nucleus collisions at the LHC from the Color Glass Condensate
Mark Mace🇺🇸 · Vladimir V. Skokov🇺🇸 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸
Simple power counting arguments in the dilute-dense framework of the Color Glass Condensate (CGC) Effective Field Theory predict that even and odd azimuthal anisotropy harmonics of two-particle correlations in proton-nucleus collisions at the LHC will respectively satisfy v^2_{2n} ~ N_{ch}^0 and v^2_{2n+1} ~ N_{ch}, where N_{ch} denotes the number of charged particles. We show that these expectations are borne out qualitatively, and even quantitatively, within systematic uncertainties, for v_2 and v_4 in comparisons with data from the ATLAS collaboration. We also observe that ATLAS data for the v_3 azimuthal harmonic are in excellent agreement with our qualitative expectation; quantitative comparisons are numerically challenging at present. The lessons from this study fully complement those gained by the recent comparison of the CGC dilute-dense framework [arXiv:1805.09342] to data from the PHENIX collaboration on small system collisions at RHIC.
hep-phnucl-exnucl-thPLB(2019)·65 citations
25*
Low-Temperature Enhancement of Semi-annihilation and the AMS-02 Positron Anomaly
Yi Cai🇨🇳 · Andrew Spray🇰🇷
Semi-annihilation is a generic feature of particle dark matter that is most easily probed by cosmic ray experiments. We explore models where the semi-annihilation cross section is enhanced at late times and low temperatures by the presence of an s-channel resonance near threshold. The relic density is then sensitive to the evolution of the dark matter temperature, and we compute expressions for the associated Boltzmann equation valid in general semi-annihilating models. At late times, a self-heating effect warms the dark matter, allowing number-changing processes to remain effective long after kinetic decoupling of the dark and visible sectors. This allows the semi-annihilation signal today to be enhanced by up to five orders of magnitude over the thermal relic cross section. As a case study, we apply this to a dark matter explanation of the positron excess seen by AMS-02. We see that unlike annihilating dark matter, our model has no difficulty fitting the data while also giving the correct relic density. However, constraints from the CMB and $γ$ -rays from the galactic centre do restrict the preferred regions of parameter space.
hep-phJHEP(2018)·12 citations
26*
Unitarity-Safe Models of Non-Minimal Inflation in Supergravity
C. Pallis🇬🇷
We show that models of chaotic inflation based on the phi^p potential and a linear non-minimal coupling to gravity, fR=1+cR phi, can be done consistent with data in the context of Supergravity, retaining the perturbative unitarity up to the Planck scale, if we employ logarithmic Kahler potentials with prefactors -p(1+n) or -p(n+1)-1, where -0.035<= n<=0.007 for p=2 or -0.0145<= n<=0.006 for p=4. Focusing, moreover, on a model employing a gauge non-singlet inflaton, we show that a solution to the mu problem of MSSM and baryogenesis via non-thermal leptogensesis can be also accommodated.
hep-phastro-ph.COhep-thEPJC(2018)·10 citations
27*
Possibility of observing charged Higgs in the single top production via its $τ$ lepton decay at LHC
Ijaz Ahmed🇩🇰 · Nadia Kausar🇩🇰 · Mahpara Ghazanfar🇩🇰
Single top quark production through weak interactions is considered to be an important source of charged Higgs in the Minimal Super Symmetric Standard Model. In the s-channel single top production having largest cross-section may appear as a propagator in the form of heavy resonance state decaying to a pair of top and bottom quark. The process under investigation is $pp \to H^{\pm} \to t b \to b b ˉ W^{\pm} \to b b ˉ τ^{\pm} ν_{τ}$ , where top quark exclusively decays into a pair of bottom quark and W boson while W boson subsequently decays to $τ$ jet and neutrino. So the final state is characterized by the presence of two b jets, hadronic $τ$ decay and missing transverse energy. Within the presence of QCD multijet and electroweak background events at LHC, it has been demonstrated that the charged Higgs signal observability is possible within the available MSSM parameter space (tan $β$ , $m_{H^{\pm}})$ respecting all experimental and theoretical constraints. In order to show the observability potential of charged Higgs, the exclusion curves at 95 $%$ confidence level and 5 $σ$ contours are plotted at different integrated luminosities with $s =$ 14 TeV.
hep-ph2 citations
28*
Massive Boson Superradiant Instability of Black Holes: Nonlinear Growth, Saturation, and Gravitational Radiation
William E. East🇨🇦
We study the superradiant instability of a massive boson around a spinning black hole in full general relativity without assuming spatial symmetries. We focus on the case of a rapidly spinning black hole in the presence of a vector boson with a Compton wavelength comparable to the black hole radius, which is the regime where relativistic effects are maximized. We follow the growth of the boson cloud through superradiance into the nonlinear regime as it spins down the black hole, reaches a maximum energy, and begins to dissipate through the emission of gravitational waves. We find that the superradiant instability can efficiently convert a significant fraction of a black hole's rotational energy into gravitational radiation.
↳ gr-qcastro-ph.HEhep-phPRL(2018)·135 citations
29*
Topology classification with deep learning to improve real-time event selection at the LHC
Thong Q. Nguyen🇺🇸 · Daniel Weitekamp III🇺🇸 · Dustin Anderson🇺🇸 · Roberto Castello🇨🇭 · Olmo Cerri🇺🇸 · Maurizio Pierini🇨🇭 · Maria Spiropulu🇺🇸 · Jean-Roch Vlimant🇺🇸
We show how event topology classification based on deep learning could be used to improve the purity of data samples selected in real time at at the Large Hadron Collider. We consider different data representations, on which different kinds of multi-class classifiers are trained. Both raw data and high-level features are utilized. In the considered examples, a filter based on the classifier's score can be trained to retain ~99% of the interesting events and reduce the false-positive rate by as much as one order of magnitude for certain background processes. By operating such a filter as part of the online event selection infrastructure of the LHC experiments, one could benefit from a more flexible and inclusive selection strategy while reducing the amount of downstream resources wasted in processing false positives. The saved resources could be translated into a reduction of the detector operation cost or into an effective increase of storage and processing capabilities, which could be reinvested to extend the physics reach of the LHC experiments.
↳ hep-excs.LGhep-phphysics.data-anComput.Softw.Big Sci.(2019)·35 citations
30*
Anomaly matching, (axial) Schwinger models, and high-T super Yang-Mills domain walls
Mohamed M. Anber🇺🇸 · Erich Poppitz🇨🇦
We study the discrete chiral- and center-symmetry 't Hooft anomaly matching in the charge- $q$ two-dimensional Schwinger model. We show that the algebra of the discrete symmetry operators involves a central extension, implying the existence of $q$ vacua, and that the chiral and center symmetries are spontaneously broken. We then argue that an axial version of the $q$ $=$ $2$ model appears in the worldvolume theory on domain walls between center-symmetry breaking vacua in the high-temperature $S U (2)$ $N$ $=$ $1$ super-Yang-Mills theory and that it inherits the discrete 't Hooft anomalies of the four-dimensional bulk. The Schwinger model results suggest that the high-temperature domain wall exhibits a surprisingly rich structure: it supports a non-vanishing fermion condensate and perimeter law for spacelike Wilson loops, thus mirroring many properties of the strongly coupled four-dimensional low-temperature theory. We also discuss generalizations to theories with multiple adjoint fermions and possible lattice tests.
↳ hep-thhep-lathep-phJHEP(2018)·63 citations
31*
Light-by-Light Scattering in a Photon-Photon Collider
T. Takahashi🇯🇵 · G. An🇨🇳 · Y. Chen🇨🇳 · W. Chou🇨🇳 · Y. Huang🇨🇳 · W. Liu🇨🇳 · W. Lu🇨🇳 · J. Lv🇨🇳 · G. Pei🇨🇳 · S. Pei🇨🇳 · C. P. Shen🇨🇳 · B. Sun🇨🇳 · C. Zhang🇨🇳 · C. Zhang🇨🇳
We studied the feasibility of observing light-by-light scattering in a photon-photon collider based on an existing accelerator complex and a commercially available laser system. We investigated the statistical significance of the signal over the QED backgrounds through a Monte Carlo simulation with a detector model. The study showed that light-by-light scattering can be observed with a statistical significance of 8 to 10 sigma in a year of operation, depending on the operating conditions.
↳ hep-exhep-phphysics.ins-detEPJC(2018)·17 citations
32*
Lattice QCD study of doubly-charmed strange baryons
Nilmani Mathur🇮🇳 · M. Padmanath🇩🇪
We present the energy spectra of the low lying doubly-charmed baryons using lattice quantum chromodynamics. We precisely predict the ground state mass of the charmed-strange Omega(cc) (1/2+) baryon to be 3712(11)(12) MeV which could well be the next doubly-charmed baryon to be discovered at the LHCb experiment at CERN. We also predict masses of other doubly-charmed strange baryons with quantum numbers 3/2+, 1/2-, and 3/2-.
↳ hep-lathep-exhep-phPRD(2019)·59 citations
33*
Robust Constraint on Lorentz Violation Using Fermi-LAT Gamma-Ray Burst Data
John Ellis🇬🇧 · Rostislav Konoplich🇺🇸 · Nikolaos E. Mavromatos🇬🇧 · Linh Nguyen🇺🇸 · Alexander S. Sakharov🇺🇸 · Edward K. Sarkisyan-Grinbaum🇨🇭
Models of quantum gravity suggest that the vacuum should be regarded as a medium with quantum structure that may have non-trivial effects on photon propagation, including the violation of Lorentz invariance. Fermi Large Area Telescope (LAT) observations of gamma-ray bursts (GRBs) are sensitive probes of Lorentz invariance, via studies of energy-dependent timing shifts in their rapidly-varying photon emissions. In this paper we analyze the Fermi-LAT measurements of high-energy gamma rays from GRBs with known redshifts, allowing for the possibility of energy-dependent variations in emission times at the sources as well as a possible non-trivial refractive index in vacuo for photons. We use statistical estimators based on the irregularity, kurtosis and skewness of bursts that are relatively bright in the 100 MeV to multi-GeV energy band to constrain possible dispersion effects during propagation. We find that the energy scale characterizing a linear energy dependence of the refractive index should exceed a few $\times 1 0^{17}$ GeV, and we estimate the sensitivity attainable with additional future sources to be detected by Fermi-LAT.
↳ astro-ph.HEgr-qchep-phPRD(2019)·81 citations
34*
Transversity parton distribution functions from lattice QCD
Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Karl Jansen🇩🇪 · Aurora Scapellato🇨🇾 · Fernanda Steffens🇩🇪
We present the first direct calculation of the transversity parton distribution function within the nucleon from lattice QCD. The calculation is performed using simulations with the light quark mass fixed to its physical value and at one value of the lattice spacing. Novel elements of the calculations are non-perturbative renormalization and extraction of a formula for the matching to light-cone PDFs. Final results are presented in the $MS$ scheme at a scale of $2$ GeV.
↳ hep-lathep-exhep-phnucl-ex+1PRD(2018)·165 citations
35*
The QCD $β$ -function On The String Worldsheet
Sergei Dubovsky🇺🇸
We consider confining strings in pure gluodynamics and its extensions with adjoint (s)quarks. We argue that there is a direct map between the set of bulk fields and the worldsheet degrees of freedom. This suggests a close link between the worldsheet $S$ -matrix and parton scattering amplitudes. We report an amusing relation between the Polchinski--Strominger amplitude responsible for the breakdown of integrability on the string worldsheet and the Yang--Mills $β$ -function \[ b_0={D_{cr}-D_{ph}\over 6}\;. \] Here $b_{0} = 11/3$ is the one-loop $β$ -function coefficient in the pure Yang--Mills theory, $D_{cr} = 26$ is the critical dimension of bosonic strings and $D_{p h} = 4$ is the dimensionality of the physical space-time we live in. A natural extension of this relation continues to hold in the presence of adjoint (s)quarks, connecting two of the most celebrated anomalies---the scale anomaly in quantum chromodynamics (QCD) and the Weyl anomaly in string theory.
↳ hep-thhep-lathep-phPRD(2018)·15 citations
36*
Holographic Magnetized Chiral Density Wave
Yanyan Bu🇨🇳 · Shu Lin🇨🇳
We explore the end point of the helical instability in finite density, finite magnetic field background discussed by Kharzeev and Yee [1]. The nonlinear solution is obtained and identified with the (magnetized) chiral density wave phase in literature. We find there are two branches of solutions, which match with the two unstable modes in [1]. At large chemical potential and magnetic field, the magnetized chiral density wave can be thermodynamically preferred over chirally symmetric phase and chiral symmetry breaking phase. Interestingly, we find an exotic state with vanishing chemical potential at large magnetic field. We also attempt to clarify the role of anomalous charge in holographic model.
↳ hep-thhep-phnucl-thCPC(2018)·8 citations
37*
Dipion photoproduction and the $Q^{2}$ evolution of the shape of the gold nucleus
Spencer R. Klein (for the STAR Collabortion)🇺🇸
Coherent photoproduction of vector mesons is sensitive to the shape of the target nucleus, as probed at four-momentum scale $Q^{2} \propto (M_{V} /2)^{2}$ . Previously STAR presented a high-statistics measurement of $d σ_{c} / d t$ for coherent $π^{+} π^{-}$ photoproduction in ultra-peripheral gold-gold collisions, and made a two-dimensional Fourier-Bessel (Hanckel) transformation to give the transverse distribution of interactions in the nucleus. Here, we study how $d σ_{c} / d t$ evolves with $Q^{2}$ . We divide the $π^{+} π^{-}$ signal into three different mass ( $Q^{2}$ ) bins to measure how $d σ_{c} / d t$ evolves with dipion mass. Furthermore, we find that the depth of the first diffractive minimum varies with pair mass. We perform a two-dimensional Fourier-Bessel transform to see how the effective transverse distribution of the interactions changes with decreasing pair mass. In the lowest mass bin, the nuclear profile is broader, which is consistent with expectations from saturation models.
↳ nucl-exhep-phPoS(2018)·9 citations
38*
Primordial Black Holes from Affleck-Dine Mechanism
Fuminori Hasegawa🇯🇵 · Masahiro Kawasaki🇯🇵
The recent observations of the gravitational waves (GWs) by LIGO-Virgo collaboration infer the increasing possibility of the primordial black holes (PBHs). Recently it was pointed out that sufficient PBHs are produced by the Affleck-Dine mechanism where inhomogeneous baryogenesis takes place due to change of the Hubble induced mass during and after inflation and forms high baryon bubbles (HBBs). The produced HBBs have large density contrasts through the QCD phase transition or stable Q-ball formation, which leads to formation of the LIGO PBHs. Furthermore, in this model stringent constraints from CMB $μ$ -distortion and pulsar timing array (PTA) experiments are completely absent. In this paper, we study the model in full details based on gravity and gauge mediated supersymmetry breaking scenarios and show that the model can explain the current GWs events evading observational constraints.
↳ astro-ph.COhep-phJCAP(2019)·25 citations
39*
A Fixed-Target Programme at the LHC: Physics Case and Projected Performances for Heavy-Ion, Hadron, Spin and Astroparticle Studies
C. Hadjidakis🇫🇷 · D. Kikoła🇵🇱 · J.P. Lansberg🇫🇷 · L. Massacrier🇫🇷 · M.G. Echevarria🇮🇹 · A. Kusina🇵🇱 · I. Schienbein🇫🇷 · J. Seixas🇵🇹 · H.S. Shao🇫🇷 · A. Signori🇺🇸 · B. Trzeciak🇳🇱 · S.J. Brodsky🇺🇸 and 20 other authors
We review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target program using the multi-TeV proton and ion LHC beams. We also provide a detailed account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed.
↳ hep-exhep-phnucl-exnucl-thPhys.Rept.(2021)·130 citations
40*
Strong Dynamics and Natural Inflation
Gary Shiu🇺🇸 · Wieland Staessens🇪🇸
We continue our investigation of the 4d effective field theory for closed string axions in Type II compactifications with D-branes. The inclusion of Stückelberg couplings for the axions requires the presence of chiral fermions at D-brane intersections, whose interactions at strong non-Abelian gauge coupling induce mass terms for the axions and scalar chiral condensate excitations, dubbed infladrons. The set-up allows for a realization of natural-like inflation with a closed string axion as inflaton and a flattened scalar potential due to the back-reaction of the more massive infladrons. We further point out that this large field inflationary model is not compromised by axionic wormhole corrections.
↳ hep-thastro-ph.COhep-phPRD(2018)·8 citations
41*
Euclidean correlators at imaginary spatial momentum and their relation to the thermal photon emission rate
Harvey B. Meyer🇩🇪
The photon emission rate of a thermally equilibrated system is determined by the imaginary part of the in-medium retarded correlator of the electromagnetic current transverse to the spatial momentum of the photon. In a Lorentz-covariant theory, this correlator can be parametrized by a scalar function $G_{R} (u \cdot K, K^{2})$ , where $u$ is the fluid four-velocity and $K$ corresponds to the momentum of the photon. We propose to compute the analytic continuation of $G_{R} (u \cdot K, K^{2})$ at fixed, vanishing virtuality $K^{2}$ , to imaginary values of the first argument, $u \cdot K = i ω_{n}$ . At these kinematics, the retarded correlator is equal to the Euclidean correlator $G_{E} (ω_{n}, k = i ω_{n})$ , whose first argument is the Matsubara frequency and the second is the spatial momentum. The Euclidean correlator, which is directly accessible in lattice QCD simulations, must be given an imaginary spatial momentum in order to realize the photon on-shell condition. Via a once-subtracted dispersion relation that we derive in a standard way at fixed $K^{2} = 0$ , the Euclidean correlator with imaginary spatial momentum is related to the photon emission rate. The relation allows for a more direct probing of the real-photon emission rate of the quark-gluon plasma in lattice QCD than the dispersion relations which have been used so far, the latter being at fixed spatial photon momentum $k$ and thus involving all possible virtualities of the photon.
↳ hep-lathep-phEPJA(2018)·17 citations
42*
Probing the Universe through the Stochastic Gravitational Wave Background
Sachiko Kuroyanagi🇯🇵 · Takeshi Chiba🇯🇵 · Tomo Takahashi🇯🇵
Stochastic gravitational wave backgrounds, predicted in many models of the early universe and also generated by various astrophysical processes, are a powerful probe of the Universe. The spectral shape is key information to distinguish the origin of the background since different production mechanisms predict different shapes of the spectrum. In this paper, we investigate how precisely future gravitational wave detectors can determine the spectral shape using single and broken power-law templates. We consider the detector network of Advanced-LIGO, Advanced-Virgo and KAGRA and the space-based gravitational-wave detector DECIGO, and estimate the parameter space which could be explored by these detectors. We find that, when the spectrum changes its slope in the frequency range of the sensitivity, the broken power-law templates dramatically improve the $χ^{2}$ fit compared with the single power-law templates and help to measure the shape with a good precision.
↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·121 citations
43*
Nuclear beta decays and CKM unitarity
J.C. Hardy🇺🇸 · I.S. Towner🇺🇸
Nuclear beta decays between (J^pi,T) = (0^+,1) analog states yield the best value for the Vud element of the Cabibbo-Kobayashi-Maskawa matrix. Current world data establish the corrected Ft values of 14 separate superallowed transitions to a precision of order 0.1% or better. The validity of the small theoretical correction terms is confirmed by excellent consistency among the 14 Ft values and by recent measurements that compare pairs of mirror superallowed transitions. With consistency established, the results now yield |Vud| = 0.97420(21). This value is consistent with the considerably less precise results obtained from beta decays of the neutron, the pion and T=1/2 mirror nuclei, which are hampered by experimental challenges.
↳ nucl-exhep-phnucl-th26 citations
44*
Is the Big Rip unreachable?
Konstantinos Dimopoulos🇬🇧
I investigate the repercussions of particle production when the Universe is dominated by a hypothetical phantom substance. I show that backreaction due to particle production prevents the density from shooting to infinity at a Big Rip, but instead forces it to stabilise at a large constant value. Afterwards there is a period of de-Sitter inflation. I speculate that this might lead to a cyclic Universe.
↳ gr-qcastro-ph.COhep-phhep-thPLB(2018)·8 citations
45*
Lattice QCD Method To Study Hadron Mass Is Not Correct
Gouranga C Nayak🇺🇸
Since the numerical path integration in the lattice QCD involves quark and gluon fields (not hadron fields) the lattice QCD cannot calculate any hadronic observable. Because of this reason the hadronic properties are extracted in the lattice QCD method by inserting complete set of hadron states $\sum_{n} ∣ n >< n ∣ = 1$ in between the partonic operators by assuming $H_{QCD} ∣ n >= E_{n} ∣ n >$ where $E_{n}$ is the energy of the hadron. However, in this paper we find $H_{QCD} ∣ n > \neq = E_{n} ∣ n >$ because the QCD hamiltonian $H_{QC D}$ is unphysical but the $E_{n}$ and $∣ n >$ of the hadron are physical. We show that this is consistent with $E_{QCD} (t) =< n ∣ H_{QC D} ∣ n > \neq = E_{n}$ due to non-zero energy flux $E_{flux} (t)$ in QCD because of confinement involving non-perturbative QCD. Hence we find that the lattice QCD method to study hadron mass is not correct.
↳ hep-lathep-phnucl-th2 citations
46*
Some remarks on the current issues in nucleon spin structure study
Israel Weimin Sun🇨🇳
I give some personal remarks on some current issues in the nucleon spin structure study. At an elementary level I propose a new angular momentum separation for the massless Dirac field in a free theory which mimics the usual free photon angular momentum separation pattern in Coulomb gauge. In connection with this construction I introduce a somewhat idiosyncratic formalism in a free massless Dirac theory which I call "dressed axial $U (1)_{A}$ symmetry". I show that this new "fermion spin operator", which is more correctly called "helicity vector operator", can be incorporated into this new symmetry pattern in a natural way. This set of "dressed axial vector current" and its corresponding charges show an interesting internal structure and may be useful in a broader physical context. I then discuss the case of the QED model with a massless Dirac fermion. In the case of covariant quantization, I give a new and correct proof that the additional term in the total angular momentum operator stemming from the gauge-fixing term does not contribute at the level of physical matrix elements, which is discussed in the relevant literature. At the level of asymptotic fields I construct the helicity vector operator of the QED theory which actually coincides with the usual projection of the total angular momentum operator when acting on a beam of collinearly moving free particles. I then consider the QCD model with only two massless light quarks. In this context I discuss the approximate concept of "asymptotic quark and gluon fields" which is relevant to the usual parton model picture and propose to use the asymptotic "quark helicity vector" operator to describe the quark helicity contribution to an IMF proton. Finally, I give some remarks on the concept of IMF itself, which show that this very concept should be understood with some reservation from a rigorous mathematical consideration.
↳ physics.gen-phhep-ph0 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.