Wed·May 20, 2020Wednesday·May 20, 2020

1. 01*

   $\rho -\omega$ mixing contribution to the measured $CP$ asymmetry of $B^{\pm }\to \omega K^{\pm }$

   Zhen-Hua Zhang🇨🇳 · Sheng Yang🇨🇳 · Xin-Heng Guo🇨🇳

   We study the $CP$ asymmetry of $B^{\pm }\to \omega K^{\pm }$ with the inclusion of the $\rho -\omega$ mixing mechanism. It is shown that the $CP$ asymmetry of $B^{\pm }\to \omega K^{\pm }$ experimentally measured ($A_{CP}^{\text{exp}}$) and conventionally defined ($A_{CP}^{\text{con}}$) are in fact different, which relation can be illustrated as $A_{CP}^{\text{exp}}=A_{CP}^{\text{con}}+\Delta A_{CP}^{\rho \omega }$, with $\Delta A_{CP}^{\rho \omega }$ the $\rho -\omega$ mixing contribution to $A_{CP}^{\text{exp}}$. $A_{CP}^{\text{exp}}$ is in fact the regional $CP$ asymmetry of $B^{\pm }\to {\pi }^{+}{\pi }^{-}{\pi }^0{K}^{\pm }$ when the invariant mass of the three pions lies in the vicinity of the $\omega$ resonance. The numerical value of $\Delta A_{CP}^{\rho \omega }$ is extracted from the experimental data of $B^{\pm }\to {\pi }^{+}{\pi }^{-}{K}^{\pm }$ and is found to be comparable with $A_{CP}^{\text{exp}}$, hence, nonnegligible. The conventionally defined $CP$ asymmetry, $A_{CP}^{\text{con}}$, is obtained from the values of $A_{CP}^{\text{exp}}$ and $\Delta A_{CP}^{\rho \omega }$, and is compared with the theoretical calculations in the literature.

   hep-phhep-exJHEP(2020)·4 citations
2. 02*

   Constraining sterile neutrinos by core-collapse supernovae with multiple detectors

   Jian Tang🇨🇳 · TseChun Wang🇨🇳 · Meng-Ru Wu🇹🇼

   The eV-scale sterile neutrino has been proposed to explain some anomalous results in experiments, \textit{such as} the deficit of reactor neutrino fluxes and the excess of ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ in LSND. This hypothesis can be tested by future core-collapse supernova neutrino detection independently since the active-sterile mixing scheme affects the flavor conversion of neutrinos inside the supernova. In this work, we compute the predicted supernova neutrino events in future detectors -- DUNE, Hyper-K, and JUNO -- for neutrinos emitted during the neutronization burst phase when the luminosity of ${\nu }_e$ dominates the other flavors. We find that for a supernova occurring within 10 kpc, the difference in the event numbers with and without sterile neutrinos allows to exclude the sterile neutrino hypothesis at more than $99\%$ confidence level robustly. The derived constraints on sterile neutrinos mixing parameters are comparably better than the results from cosmology and on-going or proposed reactor experiments by more than two orders of magnitude in the ${\sin }^{2}2{\theta }_{14}$-$\Delta m_{41}^2$ plane.

   hep-phastro-ph.GAastro-ph.HEJCAP(2020)·23 citations
3. 03*

   ${\rm Y}$ photo-production on the proton at the Electron-Ion Collider

   Oleksii Gryniuk🇩🇪 · Sylvester Joosten🇺🇸 · Zein-Eddine Meziani🇺🇸 · Marc Vanderhaeghen🇩🇪

   We present a dispersive analysis with the aim to extract the ${\rm Y}$-p scattering length from $\gamma p\to {\rm Y}p$ experiments. In this framework, the imaginary part of the ${\rm Y}$-p forward scattering amplitude is obtained from $\gamma p\to {\rm Y}p$ cross section measurements, and is constrained at high energies from existing HERA and LHC data. Its real part is calculated through a once-subtracted dispersion relation, and the subtraction constant is proportional to the ${\rm Y}$-p scattering length. We perform a feasibility study for ${\rm Y}$ photo-production experiments at an Electron-Ion Collider and discuss the sensitivity and precision that can be reached in the extraction of the ${\rm Y}$-p scattering length.

   hep-phhep-exPRD(2020)·44 citations
4. 04*

   Magnetic helicity in plasma of chiral fermions electroweakly interacting with inhomogeneous matter

   Maxim Dvornikov (IZMIRAN, Tomsk State University)🇷🇺

   We study chiral fermions electroweakly interacting with a background matter having the nonuniform density and the velocity arbitrarily depending on coordinates. The dynamics of this system is described approximately by finding the Berry phase. The effective action and the kinetic equations for right and left particles are derived. In the case of a rotating matter, we obtain the correction to the anomalous electric current and to the Adler anomaly. Then we study some astrophysical applications. Assuming that the chiral imbalance in a rotating neutron star vanishes, we obtain the rate of the magnetic helicity change owing to the interaction of chiral electrons with background neutrons. The characteristic time of the helicity change turns out to coincide with the period of the magnetic cycle of some pulsars.

   hep-phastro-ph.HENPB(2020)·1 citation
5. 05*

   A Positive Resampler for Monte Carlo Events with Negative Weights

   Jeppe R. Andersen🇬🇧 · Christian Gutschow🇬🇧 · Andreas Maier🇩🇪 · Stefan Prestel🇸🇪

   We propose the Positive Resampler to solve the problem associated with event samples from state-of-the-art predictions for scattering processes at hadron colliders typically involving a sizeable number of events contributing with negative weight. The proposed method guarantees positive weights for all physical distributions, and a correct description of all observables. A desirable side product of the method is the possibility to reduce the size of event samples produced by General Purpose Event Generators, thus lowering the resource demands for subsequent computing-intensive event processing steps. We demonstrate the viability and efficiency of our approach by considering its application to a next-to-leading order + parton shower merged prediction for the production of a $W$ boson in association with multiple jets.

   hep-phhep-exEPJC(2020)·35 citations
6. 06*

   Photon propagation in non-trivial backgrounds

   Palash B. Pal🇮🇳

   Propagation of photons (or of any spin-1 boson) is of interest in different kinds of non-trivial background, including a thermal bath, or a background magnetic field, or both. We give a unified treatment of all such cases, casting the problem as a matrix eigenvalue problem. The matrix in question is not a normal matrix, and therefore care should be given to distinguish the right eigenvectors from the left eigenvectors. The polarization vectors are shown to be right eigenvectors of this matrix, and the polarization sum formula is seen as the completeness relation of the eigenvectors. We show how this method is successfully applied to different non-trivial backgrounds.

   hep-phPRD(2020)·6 citations
7. 07*

   The simplest of them all: $t\bar{t}{W}^{\pm }$ at NLO accuracy in QCD

   Giuseppe Bevilacqua🇭🇺 · Huan-Yu Bi🇩🇪 · Heribertus Bayu Hartanto🇬🇧 · Manfred Kraus🇺🇸 · Malgorzata Worek🇩🇪

   Recent measurements of the $pp\to t\bar{t}{W}^{\pm }$ process in multi-lepton final states, as performed by the ATLAS collaboration in the context of the Higgs boson studies in the $t\bar{t}H$ channel, have shown discrepancies between theoretical predictions and experimental data. Such discrepancies have been observed both in the overall normalisation as well as in the modelling of the $t\bar{t}{W}^{\pm }$ process. With the goal of understanding and resolving the modelling issues within the SM $t\bar{t}{W}^{\pm }$ process we report on the state-of-the-art NLO QCD computation for this process. Specifically, we calculate higher-order corrections to the $e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }{e}^{+}{\nu }_{e}b\bar{b}$ and $e^{-}{\bar{\nu }}_e{\mu }^{+}{\nu }_{\mu }{e}^{-}{\bar{\nu }}_{e}b\bar{b}$ final state at the LHC with $\sqrt{s}=13$ TeV. In the computation off-shell top quarks are described by Breit-Wigner propagators, furthermore, double-, single- as well as non-resonant top-quark contributions along with all interference effects are consistently incorporated at the matrix element level. Results at NLO QCD accuracy are presented in the form of fiducial integrated and differential cross sections for two selected renormalisation and factorisation scale choices and three different PDF sets. The impact of the top quark off-shell effects on the $t\bar{t}{W}^{\pm }$ cross section is also examined by an explicit comparison to the narrow-width approximation.

   hep-phhep-exJHEP(2020)·74 citations
8. 08*

   Diurnal Effect of Sub-GeV Dark Matter Boosted by Cosmic Rays

   Shao-Feng Ge🇨🇳 · Jiang-Lai Liu🇨🇳 · Qiang Yuan🇨🇳 · Ning Zhou🇨🇳

   We point out a new type of diurnal effect for the cosmic ray boosted dark matter (DM). The DM-nucleon interactions not only allow the direct detection of DM with nuclear recoils, but also allow cosmic rays to scatter with and boost the nonrelativistic DM to higher energies. If the DM-nuclei scattering cross sections are sufficiently large, the DM flux is attenuated as it propagates through the Earth, leading to a strong diurnal modulation. This diurnal modulation provides another prominent signature for the direct detection of boosted sub-GeV DM, in addition to signals with higher recoil energy.

   hep-phhep-exPRL(2021)·73 citations
9. 09*

   Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: the subtraction function and moments of unpolarized structure functions

   Jose Manuel Alarcón (Universidad Complutense de Madrid)🇪🇸 · Franziska Hagelstein (AEC Bern)🇨🇭 · Vadim Lensky🇩🇪 · Vladimir Pascalutsa (JGU Mainz)🇩🇪

   The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory ($\chi$PT). Here we focus on the unpolarized VVCS amplitudes $T_1(\nu ,Q^2)$ and $T_2(\nu ,Q^2)$, and the corresponding structure functions $F_1(x,Q^2)$ and $F_2(x,Q^2)$. Our results are confronted, where possible, with "data-driven" dispersive evaluations of low-energy structure quantities, such as nucleon polarizabilities. We find significant disagreements with dispersive evaluations at very low momentum-transfer $Q$; for example, in the slope of polarizabilities at zero momentum-transfer. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.

   hep-phhep-latnucl-exnucl-th+1PRD(2020)·18 citations
10. 10*

    On the lightlike Lorentz violation

    J.L. Chkareuli🇬🇪 · Z. Kepuladze🇬🇪

    We consider the lightlike spontaneous Lorentz invariance violation (SLIV) appearing through the zero "length-fixing" constraint put on a gauge vector field, $A_{\mu }{A}^{\mu }=0$, and discuss its physical consequences in the framework of a conventional QED and beyond. Again, as in the timelike and spacelike SLIV cases, $A_{\mu }{A}^{\mu }=\pm M_A^2$ ($M_A$ is a scale of SLIV), while this constraint leads to an emergence of the Nambu-Goldstone modes collected in physical photon, the SLIV itself is still left unobservable unless gauge invariance in the theory is broken. At the same time, a crucial difference with the two former cases is that the asymmetrical vacuum corresponding to the lightlike Lorentz violation appears infinitely degenerated with all other vacua including the symmetrical one. We show that this degeneracy can be lifted out by introducing an extra gauge vector field being sterile with respect to an ordinary matter, though having some potential couplings with the basic $A_{\mu }$ field. A slight mixing of them makes the underlying gauge invariance to be partially broken due to which physical Lorentz invariance occurs broken as well. This may cause a variety of the Lorentz violating processes some of which are briefly discussed.

    hep-phhep-thPLB(2020)·0 citations
11. 11*

    Novel flavour-changing neutral currents in the top quark sector

    Nuno Castro🇵🇹 · Mikael Chala🇪🇸 · Ana Peixoto🇵🇹 · Maria Ramos🇵🇹

    We demonstrate that flavour-changing neutral currents in the top sector, mediated by leptophilic scalars at the electroweak scale, can easily arise in scenarios of new physics, and in particular in composite Higgs models. We moreover show that such interactions are poorly constrained by current experiments, while they can be searched for at the LHC in rare top decays and, more generally, in the channels $pp\to tS(S)+j$, with $S\to {\ell }^{+}{\ell }^{-}$. We provide dedicated analyses in this respect, obtaining that cut-off scales as large as $\Lambda \sim$ 90 TeV can be probed with an integrated luminosity of $\mathcal{L}=150$ fb${}^{-1}$.

    hep-phhep-exJHEP(2020)·12 citations
12. 12*

    Prospects for New Physics searches with ${\Lambda }_b\to \Lambda (1520){\ell }^{+}{\ell }^{-}$ decays

    Yasmine Amhis🇫🇷 · Sébastien Descotes-Genon🇫🇷 · Carla Marin Benito🇫🇷 · Martín Novoa-Brunet🇫🇷 · Marie-Hélène Schune🇫🇷

    We present the prospects of an angular analysis of the ${\Lambda }_b\to \Lambda (1520){\ell }^{+}{\ell }^{-}$ decay. Using the expected yield in the current dataset collected at the LHCb experiment, as well as the foreseen ones after the LHCb upgrades, sensitivity studies are presented to determine the experimental precision on angular observables related to the lepton distribution and their potential to identify New Physics. The forward-backward lepton asymmetry at low dilepton invariant mass is particularly promising. NP scenarios favoured by the current anomalies in $b\to s{\ell }^{+}{\ell }^{-}$ decays can be distinguished from the SM case with the data collected between the Run 3 and the Upgrade 2 of the LHCb experiment.

    hep-phhep-exEur.Phys.J.Plus(2021)·21 citations
13. 13*

    Study of the hidden charm pentaquarks ${\Lambda }_{c\bar{c}}$ above $4$ GeV

    Xuejie Liu🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳

    A dynamical calculation of the strange hidden charm pentaquark systems ${\Lambda }_{c\bar{c}}$ is performed in the framework of the quark delocalization color screening model. The effective potentials between two clusters are calculated to investigate the interaction between the baryons and mesons. The dynamic calculations indicate that the strange hidden charm pentaquark system with $I{J}^P=0{\frac{1}{2}}^{-}$ and $I{J}^P=0{\frac{3}{2}}^{-}$ can form bound states with the help of the channel-coupling. The energies of these two system are 4094.3 MeV and 4207.4 Mev, respectively. These two ${\Lambda }_{c\bar{c}}$ states are possible to be intriguing pentaquark candidates which are worth searching in experiments. Whereas, for the systems with isospin $I=1$, the effective potentials of all channels are repulsive, and there is no any bound state for these systems.

    hep-phPRC(2020)·8 citations
14. 14*

    Effective field theory for vector-like leptons and its collider signals

    Mikael Chala🇪🇸 · Paweł Kozów🇵🇱 · Maria Ramos🇵🇹 · Arsenii Titov🇮🇹

    We argue that in models with several high scales; e.g. in composite Higgs models or in gauge extensions of the Standard Model (SM), vector-like leptons can be likely produced in a relatively large $\sqrt{s}$ region of the phase space. Likewise, they can easily decay into final states not containing SM gauge bosons. This contrasts with the topology in which these new particles are being searched for at the LHC. Adopting an effective field theory approach, we show that searches for excited leptons must be used instead to test this scenario. We derive bounds on all the relevant interactions of dimension six; the most constrained ones being of about $0.05$ TeV${}^{-2}$. We build new observables to improve current analyses and study the impact on all single-field UV completions of the SM extended with a vector-like lepton that can be captured by the effective field theory at tree level, in the current and in the high-luminosity phase of the LHC.

    hep-phhep-exPLB(2020)·11 citations
15. 15*

    Planck residuals anomaly as a fingerprint of alternative scenarios to inflation

    Guillem Domènech🇩🇪 · Xingang Chen🇺🇸 · Marc Kamionkowski🇺🇸 · Abraham Loeb🇺🇸

    Planck's residuals of the CMB temperature power spectrum present a curious oscillatory shape that resembles an extra smoothing effect of lensing and is the source of the lensing anomaly. The smoothing effect of lensing to the CMB temperature power spectrum is, to some extent, degenerate with oscillatory modulations of the primordial power spectrum, in particular if the frequency is close to that of the acoustic peaks. We consider the possibility that the lensing anomaly reported by the latest Planck 2018 results may be hinting at an oscillatory modulation generated by a massive scalar field during an alternative scenario to inflation or by a sharp feature during inflation. We use the full TTTEEE+low E CMB likelihood from Planck to derive constraints on these two types of models. We obtain that in both cases the $A_L$ anomaly is mildly reduced to slightly less than $2\sigma$, to be compared with the $2.8\sigma$ deviation from $A_L=1$ in $\Lambda$CDM. Although the oscillatory features are not able to satisfactorily ease the lensing anomaly, we find that the oscillatory modulation generated during an alternative scenario alone, i.e. with $A_L=1$, presents the lowest value of ${\chi }^2$, with $\Delta {\chi }^2=-13$ compared to $\Lambda$CDM. Furthermore, the Akaike Information Criterion suggests that such an oscillation constitutes an attractive candidate since it has a value $\Delta \mathrm{AIC}=-5$ with respect to $\Lambda$CDM, comparable to the $A_L$ parameter. We also obtain that the equation of state parameter in the alternative scenario is given at $1\sigma$ by $w=0.13\pm 0.17$. Interestingly, the matter bounce and radiation bounce scenarios are compatible with our results. We discuss how these models of oscillatory features can be tested with future observations.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2020)·34 citations
16. 16*

    Apollo 11 and Fundamental Science

    A. De Rújula🇪🇸

    Half a century after a man first set foot on the moon it is interesting to revisit the occasion with a measure of hindsight. From the point of view of basic science the greatest achievement concerned the implementation of the Nordtvedt test, a precise check of Einstein's strong equivalence principle. A particle physicist may bravely interpret the result as a precise measurement of the triple-graviton coupling. Other not so profound experiments were also (unofficially) made in Apollo flights, such as a long-distance test of ESP (yes! extra sensory perception). From a sociopolitical point of view the lesson concerns the feats that can be achieved by a determined and united country... or more than one.

    ↳ physics.hist-phgr-qchep-phInference: International Review of Scienc…·0 citations
17. 17*

    The Stabilizing Effect of Gravity Made Simple

    J.R. Espinosa🇪🇸

    A new approach to vacuum decay in quantum field theory, based on a simple variational formulation in field space using a tunneling potential, is ideally suited to study the effects of gravity on such decays. The method allows to prove in new and simple ways many results, among others, that gravitational corrections tend to make Minkowski or Anti de Sitter false vacua more stable semiclassically or that higher barriers increase vacuum lifetime. The approach also offers a very clean picture of gravitational quenching of vacuum decay and its parametric dependence on the features of a potential and allows to study the BPS domain-walls between vacua in critical cases. Special attention is devoted to supersymmetric potentials and to the discussion of near-critical vacuum decays, for which it is shown how the new method can be usefully applied beyond the thin-wall approximation.

    ↳ hep-thgr-qchep-phJCAP(2020)·8 citations
18. 18*

    Transport in neutron star mergers

    Steven P. Harris🇺🇸

    After an introduction to the QCD phase diagram, the nuclear equations of state, and neutron star mergers, I discuss three projects related to transport and nuclear matter in neutron star mergers. The first is the nature of beta equilibrium in the portion of a merger that is transparent to neutrinos. We calculate the weak interaction (Urca) rates and find that the beta equilibrium condition needs to be modified by adding an additional chemical potential, which changes slightly the particle content in neutrino-transparent beta equilibrium. Secondly, we calculate the bulk viscosity in neutrino-transparent nuclear matter in conditions encountered in neutron star mergers. Bulk viscosity arises from a phase lag between the pressure and density in the nuclear matter, which is due to the finite rate of beta equilibration. When bulk viscosity is sufficiently strong, which happens when the equilibration rate nearly matches the frequency of the density oscillation, it can noticeably dampen the oscillation. We find that in certain thermodynamic conditions likely encountered in mergers, oscillations in nuclear matter can be damped on timescales on the order of 10 milliseconds, so we conclude that bulk viscosity should be included in merger simulations. Finally, we study thermal transport due to axions in neutron star mergers. We conclude that axions are never trapped in mergers, but instead escape, carrying energy away from the merger. We calculate the cooling time due to the energy carried away by axions and find that within current constraints on the axion-nucleon coupling, axions could cool fluid elements in mergers on timescales which could affect the dynamics of the merger.

    ↳ nucl-thastro-ph.HEgr-qchep-phProQuest Dissertations Publishing, 2020. …·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.