Thu·Feb 27, 2020Thursday·February 27, 2020

1. 01*

   Flavour anomalies from a split dark sector

   Luc Darmé🇮🇹 · Marco Fedele🇪🇸 · Kamila Kowalska🇵🇱 · Enrico Maria Sessolo🇵🇱

   We investigate solutions to the flavour anomalies in $B$ decays based on loop diagrams of a "split" dark sector characterised by the simultaneous presence of heavy particles at the TeV scale and light particles around and below the $B$-meson mass scale. We show that viable parameter space exists for solutions based on penguin diagrams with a vector mediator, while minimal constructions relying on box diagrams are in strong tension with the constraints from the LHC, LEP, and the anomalous magnetic moment of the muon. In particular, we highlight a regime where the mediator lies close to the $B$-meson mass, naturally realising a resonance structure and a $q^2$-dependent effective coupling. We perform a full fit to the relevant flavour observables and analyse the constraints from intensity frontier experiments. Besides new measurements of the anomalous magnetic moment of the muon, we find that decays of the $B$ meson, $B_s$-mixing, missing energy searches at Belle-II, and LHC searches for top/bottom partners can robustly test these scenarios in the near future.

   hep-phhep-exJHEP(2020)·23 citations
2. 02*

   Heavy Quark Energy Loss in the Quark-Gluon Plasma in the Moller theory

   B. Blok (Technion)🇮🇱

   We study the energy loss of a heavy quark propagating in the Quark-Gluon Plasma (QGP) in the framework of the Moller theory, including possible large Coulomb logarithms as a perturbation to BDMPSZ bremsstrahlung, described in the Harmonic Oscillator (HO) approximation. We derive the analytical expression that describes the energy loss in the entire emitted gluon frequency region. In the small frequencies region, for angles larger than the dead cone angle, the energy loss is controlled by the BDMPSZ mechanism, while for larger frequencies it is described by N=1 term in the GLV opacity expansion. We estimate corresponding quenching rates for different values of the heavy quark path and different $m/E$ ratios.

   hep-phhep-exnucl-exnucl-thEPJC(2020)·5 citations
3. 03*

   Enhanced $\Gamma (p\to K^0{\mu }^{+})/\Gamma (p\to K^{+}{\bar{\nu }}_{\mu })$ as a Signature of Minimal Renormalizable SUSY $SO(10)$ GUT

   Naoyuki Haba🇯🇵 · Yukihiro Mimura🇯🇵 · Toshifumi Yamada🇯🇵

   The ratio of the partial widths of some dimension-5 proton decay modes can be predicted without detailed knowledge of SUSY particle masses, and thus allows us to experimentally test various SUSY GUT models without discovering SUSY particles. In this paper, we study the ratio of the partial widths of the $p\to K^0{\mu }^{+}$ and $p\to K^{+}{\bar{\nu }}_{\mu }$ decays in the minimal renormalizable SUSY $SO(10)$ GUT, under only a plausible assumption that the 1st and 2nd generation left-handed squarks are mass-degenerate. In the model, we expect that the Wilson coefficients of dimension-5 operators responsible for these modes are on the same order and that the ratio of $p\to K^0{\mu }^{+}$ and $p\to K^{+}{\bar{\nu }}_{\mu }$ partial widths is $O(0.1)$. Hence, we may be able to detect both $p\to K^0{\mu }^{+}$ and $p\to K^{+}{\bar{\nu }}_{\mu }$ decays at Hyper-Kamiokande, thereby gaining a hint for the minimal renormalizable SUSY $SO(10)$ GUT. Moreover, since this partial width ratio is quite suppressed in the minimal $SU(5)$ GUT, it allows us to distinguish the minimal renormalizable SUSY $SO(10)$ GUT from the minimal $SU(5)$ GUT. In the main body of the paper, we perform a fitting of the quark and lepton masses and flavor mixings with the Yukawa couplings of the minimal renormalizable $SO(10)$ GUT, and derive a concrete prediction for the partial width ratio based on the fitting results. We find that the partial width ratio generally varies in the range 0.05-0.6, confirming the above expectation.

   hep-phPTEP(2020)·7 citations
4. 04*

   Identifying the ${\Lambda }_b(6146{)}^0$ and ${\Lambda }_b(6152{)}^0$ as $D$-wave bottom baryons

   Qiang Mao🇨🇳 · Hua-Xing Chen🇨🇳 · Hui-Min Yang🇨🇳

   We study the ${\Lambda }_b(6146{)}^0$ and ${\Lambda }_b(6152{)}^0$ recently observed by LHCb using the method of QCD sum rules within the framework of heavy quark effective theory. Our results suggest that they can be interpreted as $D$-wave bottom baryons of $J^P=3/2^{+}$ and $5/2^{+}$ respectively, both of which contain two $\lambda$-mode excitations. We also investigate other possible assignments containing $\rho$-mode excitations. We predict masses of their strangeness partners to be $m_{{\Xi }_b(3/2^{+})}=6.26_{-0.14}^{+0.11}$ GeV and $m_{{\Xi }_b(5/2^{+})}=6.26_{-0.14}^{+0.11}$ GeV with the mass splitting $\Delta M=4.5_{-1.5}^{+1.9}$ MeV, and propose to search for them in future LHCb and CMS experiments.

   hep-phhep-exhep-latUniverse(2020)·11 citations
5. 05*

   Composite Higgs Bosons and Mini Black Holes

   Christopher T. Hill🇺🇸

   Pairs of standard model fermions can annihilate to produce mini black holes with gauge quantum numbers of the Higgs boson at $M_{Planck}$. This leads to a Nambu-Jona-Lasinio model at the Planck scale with strong coupling which binds fermion pairs into Higgs fields. At critical coupling the renormalization group dresses these objects, which then descend in scale to emerge as OBSERVABLE boundstate Higgs bosons at low energies, and we obtain the multi-Higgs spectrum of a "scalar democracy." The observed Higgs boson is a gravitationally bound $\bar{t}t$ composite. Sequential states may be seen at the LHC, and/or its upgrades.

   hep-phgr-qchep-th3 citations
6. 06*

   IFI and ISR Effects for Z/${\gamma }^{\ast }$ Drell-Yan Observables using $\mathcal{KK}$MC-hh

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

   Continuing with our investigations of the expected sizes of multiple photon radiative effects in heavy gauge boson production with decay to charged lepton pairs in the context of the precision physics of the LHC, using \KK{MC}-hh 4.22 we consider IFI and ISR effects for specific Z/${\gamma }^{\ast }$ Drell-Yan observables measured by the ATLAS and CMS Collaborations. With this version of \KK{MC}-hh, we have coherent exclusive exponentiation (CEEX) electroweak (EW) exact $\mathcal{O}({\alpha }^{2}L)$ corrections in a hadronic MC and control over the corresponding EW initial-final interference (IFI) effects as well. Specifically, we illustrate the interplay between cuts of the type used in the measurement of $A_{FB}$ and $A_4$ at the LHC and the sizes of the expected responses of the attendant higher order corrections. We find that there are per cent to per mille level effects in the initial-state radiation, fractional per mille level effects in the IFI and per mille level effects in the over-all $\mathcal{O}({\alpha }^{2}L)$ corrections that any treatment of EW corrections at the per mille level should consider. Our results are applicable to current LHC experimental data analyses.

   hep-ph13 citations
7. 07*

   Chiral perturbation theory for nonzero chiral imbalance

   Domènec Espriu🇪🇸 · Angel Gómez Nicola🇪🇸 · Andrea Vioque-Rodríguez🇪🇸

   We construct the most general low-energy effective lagrangian including local parity violating terms parametrized by an axial chemical potential or chiral imbalance ${\mu }_5$, up to $\mathcal{O}(p^4)$ order in the chiral expansion for two light flavours. For that purpose, we work within the Chiral Perturbation Theory framework where only pseudo-NGB fields are included, following the external source method. The $\mathcal{O}(p^2)$ lagrangian is only modified by constant terms, while the $\mathcal{O}(p^4)$ one includes new terms proportional to ${\mu }_5^2$ and new low-energy constants (LEC), which are renormalized and related to particular observables. In particular, we analyze the corrections to the pion dispersion relation and observables related to the vacuum energy density, namely the light quark condensate, the chiral and topological susceptibilities and the chiral charge density, providing numerical determinations of the new LEC when possible. In particular, we explore the dependence of the chiral restoration temperature $T_c$ with ${\mu }_5$. An increasing $T_c({\mu }_5)$ is consistent with our fits to lattice data of the ChPT-based expressions. Although lattice uncertainties are still large and translate into the new LEC determination, a consistent physical description of those observables emerges from our present work, providing a theoretically robust model-independent framework for further study of physical systems where parity-breaking effects may be relevant, such as heavy-ion collisions.

   hep-phJHEP(2020)·20 citations
8. 08*

   Searching Inert Scalars at Future e${}^{+}$e${}^{-}$ Colliders

   Aleksander Filip Zarnecki🇵🇱 · Jan Kalinowski🇵🇱 · Jan Klamka🇵🇱 · Pawel Sopicki🇵🇱 · Wojciech Kotlarski🇩🇪 · Tania Robens🇭🇷 · Dorota Sokolowska🇧🇷

   The Inert Doublet Model (IDM) is one of the simplest extensions of the Standard Model (SM), providing a dark matter candidate. It is a two Higgs doublet model with a discrete $Z_2$ symmetry, that prevents the scalars of the second doublet (inert scalars) from coupling to the SM fermions and makes the lightest of them stable. We study a large number of IDM scenarios, which are consistent with current constraints on direct detection and relic density of dark matter, as well as with all collider and low-energy limits. We propose a set of benchmark points with different kinematic features, that promise detectable signals at future $e^{+}{e}^{-}$ colliders. Two inert scalar pair-production processes are considered, $e^{+}{e}^{-}\to AH$ and $e^{+}{e}^{-}\to H^{+}{H}^{-}$, followed by decays of $A$ and $H^{\pm }$ into final states which always include the lightest and stable neutral scalar dark matter candidate $H$. Significance of the expected observations is studied for different benchmark models and different running scenarios, for centre-of-mass energies from 250 GeV up to 3 TeV. For low mass scenarios, high significance can be obtained for the signal signatures with two muons or an electron and a muon in the final state. For high mass scenarios, which are only accessible at high energy stages of CLIC, the significance is too low for the leptonic signature and the semi-leptonic final state has to be used as the discovery channel. Results presented for this channel are based on the fast simulation of the CLIC detector response with the DELPHES package.

   hep-ph14 citations
9. 09*

   Scalar spectrum in a graviton soft wall model

   Matteo Rinaldi🇮🇹 · Vicente Vento🇪🇸

   In this study we present a unified phenomenological analysis of the scalar glueball and scalar meson spectra within an AdS/QCD framework in the bottom up approach. For this purpose we generalize the recently developed graviton soft-wall (GSW) model, which has shown an excellent agreement with the lattice QCD glueball spectrum, to a description of glueballs and mesons with a unique energy scale. In this scheme, dilatonic effects, are incorporated in the metric as a deformation of the AdS space. We apply the model also to the heavy meson spectra with success. We obtain quadratic mass equations for all scalar mesons while the glueballs satisfy an almost linear mass equation. Besides their spectra, we also discuss the mixing of scalar glueball and light scalar meson states within a unified framework: the GSW model. To this aim, the light-front holographic approach, which connects the mode functions of AdS/QCD to the light-front wave functions, is applied. This relation provides the probabilistic interpretation required to properly investigate the mixing conditions.

   hep-phnucl-thJ.Phys.G(2020)·20 citations
10. 10*

    Shear transport far from equilibrium via holography

    Michael F. Wondrak🇩🇪 · Matthias Kaminski🇺🇸 · Marcus Bleicher🇩🇪

    In heavy-ion collisions, the quark-gluon plasma is produced far from equilibrium. This regime is currently inaccessible by quantum chromodynamics (QCD) computations. We calculate shear transport and entropy far from equilibrium in a holographic model, defining a time-dependent ratio of shear viscosity to entropy density, $\eta /s$. Large deviations of up to 60% from its near-equilibrium value, $1/4\pi$, are found for realistic situations at the Large Hadron Collider. We predict the far-from-equilibrium time-dependence of $\eta /s$ to substantially affect the evolution of the QCD plasma and to impact the extraction of QCD properties from flow coefficients in heavy-ion collision data.

    hep-phhep-thnucl-thPLB(2020)·20 citations
11. 11*

    Novel approach to neutron electric dipole moment search using weak measurement

    Daiki Ueda🇯🇵 · Teppei Kitahara🇮🇱

    We propose a novel approach in a search for the neutron electric dipole moment (EDM) by taking advantage of signal amplification in a weak measurement, known as weak value amplification. Considering an analogy to the weak measurement that can measure the spin magnetic moment interaction, we examine an experimental setup with a polarized neutron beam through an external electric field with spatial gradient, where the signal is sensitive to the EDM interaction. In particular, a dedicated analysis of effects from impurities in pre- and post-selections is performed. We show that the weak value amplification occurs where the signal is enhanced by up to two orders of magnitude, and demonstrate a potential sensitivity of the proposed setup to the neutron EDM.

    hep-phhep-exquant-phJ.Phys.B(2021)·2 citations
12. 12*

    New Constraints on Millicharged Particles from Cosmic-ray Production

    Ryan Plestid🇺🇸 · Volodymyr Takhistov🇺🇸 · Yu-Dai Tsai🇺🇸 · Torsten Bringmann🇳🇴 · Alexander Kusenko🇺🇸 · Maxim Pospelov🇺🇸

    We study the production of exotic millicharged particles (MCPs) from cosmic ray-atmosphere collisions which constitutes a permanent MCP production source for all terrestrial experiments Our calculation of the MCP flux can be used to reinterpret existing limits from experiments such as MACRO and Majorana on an ambient flux of ionizing particles. Large-scale underground neutrino detectors are particularly favorable targets for the resulting MCPs. Using available data from the Super-K experiment, we set new limits on MCPs, which are the best in sensitivity reach for the mass range $0.1\lesssim m_{\chi }\lesssim 0.5$ GeV, and which are competitive with accelerator-based searches for masses up to 1.5 GeV. Applying these constraints to models where a sub-dominant component of dark matter (DM) is fractionally charged allows us to probe parts of the parameter space that are challenging for conventional direct-detection DM experiments, independently of any assumptions about the DM abundance. These results can be further improved with the next generation of large-scale neutrino detectors.

    hep-phastro-ph.COhep-exPRD(2020)·117 citations
13. 13*

    Higgs Inflation as Nonlinear Sigma Model and Scalaron as its $\sigma$-meson

    Yohei Ema🇩🇪 · Kyohei Mukaida🇩🇪 · Jorinde van de Vis🇩🇪

    We point out that a model with scalar fields with a large nonminimal coupling to the Ricci scalar, such as Higgs inflation, can be regarded as a nonlinear sigma model (NLSM). With the inclusion of not only the scalar fields but also the conformal mode of the metric, our definition of the target space of the NLSM is invariant under the frame transformation. We show that the $\sigma$-meson that linearizes this NLSM to be a linear sigma model (LSM) corresponds to the scalaron, the degree of freedom associated to the $R^2$ term in the Jordan frame. We demonstrate that quantum corrections inevitably induce this $\sigma$-meson in the large-$N$ limit, thus providing a frame independent picture for the emergence of the scalaron. The resultant LSM only involves renormalizable interactions and hence its perturbative unitarity holds up to the Planck scale unless it hits a Landau pole, which is in agreement with the renormalizability of quadratic gravity.

    hep-phastro-ph.COgr-qchep-thJHEP(2020)·44 citations
14. 14*

    Small-mass naked singularities censored by the Higgs field

    Naritaka Oshita🇨🇦

    We investigate a vacuum decay around an over-spinning naked singularity by using the Israel junction condition. We found that if the Higgs field develops the second minimum at higher energy scale, a spinning small-mass naked singularity could cause the vacuum decay around it within the cosmic age. An event horizon may form around the singularity due to the angular momentum transport from the singularity to a vacuum bubble wall. The newly formed event horizon leads to the increase of Bekenstein-Hawking entropy, which contributes to the enhancement of the vacuum decay rate. We conclude that small-mass naked singularities may be hidden by the event horizon within the cosmological time.

    ↳ hep-thgr-qchep-phClass.Quant.Grav.(2020)·4 citations
15. 15*

    Reconstructing particle number distributions with convoluting volume fluctuations

    ShinIchi Esumi🇯🇵 · Kana Nakagawa🇯🇵 · Toshihiro Nonaka🇯🇵

    We propose methods to reconstruct particle distributions with and without considering initial volume fluctuations. This approach enables us to correct for detector efficiencies and initial volume fluctuations simultaneously. Our study suggests such a tool could investigate the possible bimodal structure of net-proton distribution in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$7.7 GeV a signature of first-order phase transition and critical point [arXiv:1804.04463,arXiv:1811.04456].

    ↳ physics.data-anhep-phnucl-exNucl.Instrum.Meth.A(2021)·14 citations
16. 16*

    Chiral Radiation Transport Theory of Neutrinos

    Naoki Yamamoto🇯🇵 · Di-Lun Yang🇯🇵

    We construct the chiral radiation transport equation for left-handed neutrinos in the context of radiation hydrodynamics for core-collapse supernovae. Based on the chiral kinetic theory incorporating quantum corrections due to the chirality of fermions, we derive a general relativistic form of the chiral transfer equation with collisions. We show that such quantum corrections explicitly break the spherical symmetry and axisymmetry of the system. In the inertial frame, in particular, we find that the so-called side jump leads to quantum corrections in the collisions between neutrinos and matter. We also derive analytic forms of such corrections in the emission and absorption rates for the neutrino absorption process. These corrections result in the generation of kinetic helicity and cross helicity of matter, which should then modify the subsequent evolution of matter. This theoretical framework can be applied to investigate the impacts of the chirality of neutrinos on the evolution of core-collapse supernovae.

    ↳ astro-ph.HEhep-phnucl-thApJ(2020)·36 citations
17. 17*

    Combined analysis of AMS-02 (Li,Be,B)/C, N/O, 3He, and 4He data

    Nathanael Weinrich🇫🇷 · Yoann Génolini🇩🇰 · Mathieu Boudaud🇪🇸 · Laurent Derome🇫🇷 · David Maurin🇫🇷

    The AMS-02 experiment measured several secondary-to-primary ratios enabling a detailed study of Galactic cosmic-ray transport. We constrain previously derived benchmark scenarios (based on AMS-02 B/C data only) using other secondary-to-primary ratios, to test the universality of transport and the presence of a low-rigidity diffusion break. We use the 1D thin disc/thick halo propagation model of USINE and a ${\chi }^2$ minimisation accounting for a covariance matrix of errors (AMS-02 systematics) and nuisance parameters (cross-sections and solar modulation uncertainties). The combined analysis of AMS-02 Li/C, Be/C, and B/C strengthens the case for a diffusion slope of $\delta =0.50\pm 0.03$ with a low-rigidity break or upturn of the diffusion coefficient at GV rigidities. Our simple model can successfully reproduce all considered data (Li/C, Be/C, B/C, N/O, and 3He/4He), although several issues remain: (i) the quantitative agreement depends on the assumptions made on the not well constrained correlation lengths of AMS-02 data systematics; (ii) combined analyses are very sensitive to production cross sections, and we find post-fit values differing by $\sim 5-15\%$ from their most likely values (roughly within currently estimated nuclear uncertainties); (iii) two very distinct regions of the parameter space remain viable, either with reacceleration and convection, or with purely diffusive transport. To take full benefit of combined analyses of AMS-02 data, better nuclear data and a better handle on energy correlations in the data systematic are required. AMS-02 data on heavier species are eagerly awaited to further explore cosmic-ray propagation scenarios.

    ↳ astro-ph.HEhep-phAstron.Astrophys.(2020)·83 citations
18. 18*

    Measurement of the charge separation along the magnetic field with Signed Balance Function in 200 GeV Au + Au collisions at STAR

    Yufu Lin (for the STAR Collaboration)🇨🇳

    Experimental searches for Chiral Magnetic Effect (CME) in heavy-ion collisions have been going on for a decade, and so far there is no conclusive evidence for its existence. Recently, the Signed Balance Function (SBF), based on the idea of examining the momentum ordering of charged pairs along the in- and out-of-plane directions, has been proposed as a probe of CME. In this approach, a pair of observables is invoked: one is $r_{\mathrm{rest}}$, the out-of-plane to in-plane ratio of $\Delta B$ measured in pair's rest frame, where $\Delta B$ is the difference between signed balance functions; The other is a double ratio, $R_{\mathrm{B}}=r_{\mathrm{rest}}/r_{\mathrm{lab}}$, where $r_{\mathrm{lab}}$ is a measurement similar to $r_{\mathrm{rest}}$ but measured in the laboratory frame. These two observables give opposite responses to the CME-driven charge separation compared to the background correlations arising from resonance flow and global spin alignment. Both $r_{\mathrm{rest}}$ and $R_{\mathrm{B}}$ being larger than unity can be regarded as a case in favor of the existence of CME. It is found experimentally that $r_{\mathrm{rest}}$, $r_{\mathrm{lab}}$ and $R_{\mathrm{B}}$ are larger than unity in Au+Au collisions at 200 GeV, and larger than realistic model calculations with no CME implemented. These findings are difficult to be explained by a background-only scenario.

    ↳ nucl-exhep-exhep-phnucl-thNPA(2021)·8 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.