Thu·May 14, 2020Thursday·May 14, 2020

1. 01*

   Parametrically narrow tetraquark states containing one heavy quark and one heavy antiquark

   Yiming Cai🇺🇸 · Thomas Cohen🇺🇸

   This paper focuses on tetraquarks containing one heavy quark and one heavy antiquark in the formal limit where the heavy quark masses go to infinity. It extends the theoretical framework developed for tetraquark containing two heavy quarks based on semi-classical analysis and the Born-Oppenheimer approximation. It is shown that for sufficiently small light quark masses, parametrically narrow $q{\bar{q}}^{\prime }Q\bar{Q}$ tetraquarks must exist in the formal limit of arbitrarily large heavy quark masses. The analysis is model-independent; it requires no assumptions about the structure of the state or the mechanism of its decay beyond what can be deduced directly from QCD. The formal analysis here is only directly applicable to tetraquarks with large angular momentum and hence does not directly apply to experimentally observed tetraquark candidates. We also discuss the condition needed for a version of the analysis to apply for low angular momenta states. Whether this condition holds can be explored via lattice calculations. Current lattice calculations suggest that the condition is not met. If these preliminary calculations are confirmed, there are strong implications for the nature of the observed tetraquark resonances containing $\bar{c}c$ or $\bar{b}b$ pairs. It raises the possibility that the observed tetraquarks exist and are narrow not because the charm and bottom quarks are extremely heavy, but because they are sufficiently light.

   hep-phPRD(2020)·0 citations
2. 02*

   Photonic production of the pair of $B_c$ mesons

   A.E. Dorokhov🇷🇺 · R.N. Faustov🇷🇺 · A.P. Martynenko🇷🇺 · F.A. Martynenko🇷🇺

   We study the pair production of $B_c$ mesons in the photon-photon interaction in the framework of perturbative quantum chromodynamics and the relativistic quark model. The production amplitudes of a pair of pseudoscalar and vector $B_c$ mesons are constructed in the nonrelativistic approximation and taking into account relativistic effects. Relativistic corrections related to the relative motion of heavy quarks in the production amplitude, as well as in the wave function of the bound state of heavy quarks, are taken into account. Analytical expressions are constructed for the relativistic differential and total cross sections for the pair $B_c$ meson production. Based on them, numerical values of the production cross sections are obtained for various energies and scattering angles.

   hep-phPRD(2020)·9 citations
3. 03*

   CP Violation in $B^{\pm }\to {\rho }^0{\pi }^{\pm }$ and $B^{\pm }\to \sigma {\pi }^{\pm }$ Decays

   Hai-Yang Cheng🇹🇼

   The decay amplitude of $B^{+}\to {\pi }^{+}{\pi }^{-}{\pi }^{+}$ in the Dalitz plot has been analyzed by the LHCb using three different approaches for the $S$-wave component. It was found that the mode with $\sigma$ (or $f_0(500)$) exhibited a CP asymmetry of 15\% in the isobar model, whereas the $f_2(1270)$ mode had a 40\% asymmetry. On the contrary, CP asymmetry for the dominant quasi-two-body decay $B^{-}\to {\rho }^0{\pi }^{-}$ was found to be consistent with zero in all three approaches, while all the existing theoretical predictions lead to a negative CP asymmetry ranging from $-7\%$ to $-45\%$. We show that the nearly vanishing CP violation in $B^{-}\to {\rho }^0{\pi }^{-}$ is understandable in the framework of QCD factorization (QCDF). It arises from the $1/m_b$ power corrections to the penguin amplitudes due to penguin annihilations and to the color-suppressed tree amplitude due to hard spectator interactions. Penguin annihilation and hard spectator interactions contribute destructively to $A_{CP}(B^{-}\to {\rho }^0{\pi }^{-})$ to render it consistent with zero. The branching fraction and CP asymmetry in $B^{-}\to \sigma /f_0(500){\pi }^{-}$ are investigated in QCDF with results in agreement with experiment.

   hep-phhep-ex15 citations
4. 04*

   Generalized King linearity and new physics searches with isotope shifts

   Julian C. Berengut🇦🇺 · Cédric Delaunay🇫🇷 · Amy Geddes🇦🇺 · Yotam Soreq🇮🇱

   Atomic spectral lines for different isotopes are shifted, revealing a change in the properties of the nucleus. For spinless nuclei such isotope shifts for two distinct transitions are expected to be linearly related, at least at leading order in a change of the nuclear mass and charge distribution. Looking for a breaking of linearity in so-called King plots was proposed as a novel method to search for physics beyond the standard model. In the light of the recent experimental progress in isotope shift spectroscopy, the sensitivity of these searches will become limited by the determination of the isotope masses and/or by nuclear effects which may induce nonlinearities at an observable level. In this work, we propose two possible generalizations of the traditional King plot that overcome these limitations by including additional isotope shift measurements, thus significantly extending the new physics reach of King plots in a purely spectroscopy-driven approach.

   hep-phhep-exphysics.atom-phPRResearch(2020)·66 citations
5. 05*

   String Fragmentation with a Time-Dependent Tension

   Nicholas Hunt-Smith🇦🇺 · Peter Skands🇦🇺

   Motivated by recent theoretical arguments that expanding strings can be regarded as having a temperature that is inversely proportional to the proper time, tau, we investigate the consequences of adding a term proportional to 1/tau to the string tension in the Lund string-hadronization model. The lattice value for the tension, kappa0 ~ 0.18 GeV^2 ~ 0.9 GeV/fm, is then interpreted as the late-time/equilibrium limit. A generic prediction of this type of model is that early string breaks should be associated with higher strangeness (and baryon) fractions and higher fragmentation <pT> values. It should be possible to use archival ee data sets to provide model-independent constraints on this type of scenario, and we propose a few simple key measurements to do so.

   hep-phEPJC(2020)·14 citations
6. 06*

   Renormalization group and scattering-equivalent Hamiltonians on a coarse momentum grid

   María Gómez-Rocha🇪🇸 · Enrique Ruiz Arriola🇪🇸

   We consider the $\pi \pi$-scattering problem in the context of the Kadyshevsky equation. In this scheme, we introduce a momentum grid and provide an isospectral definition of the phase-shift based on the spectral shift of a Chebyshev angle. We address the problem of the unnatural high momentum tails present in the fitted interactions which reaches energies far beyond the maximal center-of-mass energy of $\sqrt{s}=1.4$ GeV. It turns out that these tails can be integrated out by using a block-diagonal generator of the SRG.

   hep-phnucl-thActa Phys.Polon.Supp.(2021)·1 citation
7. 07*

   Dark Matter Abundance from Sequential Freeze-in Mechanism

   Genevieve Belanger🇫🇷 · Cedric Delaunay🇫🇷 · Alexander Pukhov🇷🇺 · Bryan Zaldivar🇪🇸

   We present a thorough analysis of the sequential freeze-in mechanism for dark matter production in the early universe. In this mechanism the dark matter relic density results from pair annihilation of mediator particles which are themselves produced by thermal collisions of standard model particles. Below some critical value of the mediator coupling to standard model fields, this sequential channel dominates over the usual freeze-in where dark matter is directly produced from thermal collisions, even when the mediator is not in thermal equilibrium. The latter case requires computing the full non-thermal distribution of the mediators, for which finite temperature corrections are particularly important.

   hep-phPRD(2020)·40 citations
8. 08*

   A possible simultaneous fit to the available $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross section data nearby $\psi (4660)$ by means of a strong correction to the Coulomb enhancement factor

   Antonio Amoroso🇮🇹 · Stefano Bagnasco🇮🇹 · Rinaldo Baldini Ferroli🇮🇹 · Ilaria Balossino🇮🇹 · Monica Bertani🇮🇹 · Diego Bettoni🇮🇹 · Fabrizio Bianchi🇮🇹 · Alberto Bortone🇮🇹 · Alessandro Calcaterra🇮🇹 · Gianluigi Cibinetto🇮🇹 · Fabio Cossio🇮🇹 · Francesca De Mori🇮🇹 and 21 other authors

   There are two available set of data on the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ cross section above threshold. The BELLE measurement, with ISR return, is compatible with the presence of a resonant state, called $\psi (4660)$ (formerly known as $Y(4660)$), observed also in other final states. The BESIII dataset has shown a different trend, with a flat cross section. We propose a new solution to fit both datasets by means of a strong correction to the Coulomb enhancement factor. Mass and width of the resonant state is extracted.

   hep-ph0 citations
9. 09*

   Constraints of the Low-x Structure of Protons and Nuclei

   Thomas Peitzmann🇳🇱

   I review recent developments in the study of the low-x partonic content of protons and nuclei, with a focus on the latter, as one expects possible deviations from linear QCD evolution to be most pronounced in that case. I give examples of recent theoretical descriptions of HERA measurements with a focus on the role of BFKL evolution. I then concentrate on the status and assumptions of nuclear PDFs and the possibility to use forward particle production at the LHC as further constraint, in particular measurements of open charm and the potential of electromagnetic probes.

   hep-phEPJ Web Conf.(2020)·0 citations
10. 10*

    Semileptonic decays $D\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ and $D_s\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ as the probe of constituent quark-antiquark pairs in the light scalar mesons

    N.N. Achasov🇷🇺 · A.V. Kiselev🇷🇺 · G.N. Shestakov🇷🇺

    Decays $D\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ and $D_s\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ serve as probes that check the existence of constituent $q\bar{q}$ components in the wave functions of scalar mesons decaying into ${\pi }^{+}{\pi }^{-}$. There exists a great deal of concrete evidence in favor of the exotic four-quark nature of light scalars. At the same time, the further expansion of the area of the $q^2{\bar{q}}^2$ model validity for light scalars on ever new processes seems extremely interesting and important. We analyze the BESIII and CLEO data on the decays $D^{+}\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ and $D_s^{+}\to {\pi }^{+}{\pi }^{-}{e}^{+}{\nu }_e$ and show that the results of these experiments together can be interpreted in favor of the four-quark nature of light scalar mesons $\sigma (500)$ and $f_0(980)$. Our approach can also be applied to the description of other similar decays involving light scalars.

    hep-phhep-exnucl-thPRD(2020)·20 citations
11. 11*

    High $p_T$ correlated tests of lepton universality in lepton(s) + jet(s) processes; an EFT analysis

    Yoav Afik🇮🇱 · Shaouly Bar-Shalom🇮🇱 · Jonathan Cohen🇮🇱 · Amarjit Soni🇺🇸 · Jose Wudka🇺🇸

    We suggest a new class of tests for searching for lepton flavor non-universality (LFNU) using ratio observables and based on correlations among the underlying LFNU new physics (NP) effects in several (seemingly independent) di-lepton and single lepton + jet(s) processes. This is demonstrated by studying the effects generated by LFNU 4-Fermi interactions involving 3rd generation quarks. We find that the sensitivity to the scale ($\Lambda$) of the LFNU 4-Fermi operators significantly improves when the correlations among the various di-lepton +jets and single-lepton + jets processes are used, reaching $\Lambda \sim \mathcal{O}(10)$~TeV at the HL-LHC.

    hep-phhep-exPLB(2020)·13 citations
12. 12*

    Twin Cogenesis

    Wan-Zhe Feng🇨🇳 · Jiang-Hao Yu🇨🇳

    We investigate a cogenesis mechanism within the twin Higgs setup which can naturally explain the nature of dark matter, the cosmic coincidence puzzle, little hierarchy problem, leptogenesis and the tiny neutrino masses. Three heavy Majorana neutrinos are introduced to the standard model sector and the twin sector respectively, which explain the tiny neutrino masses and generate the lepton asymmetry and the twin lepton asymmetry at the same time. The twin cogenesis mechanism applies to any viable twin Higgs model without an explicit ${\mathbb{Z}}_2$ breaking in the leptonic sector and evading the $\Delta N_{\mathrm{eff}}$ constraint. We illustrate the twin cogenesis mechanism using the neutrino-philic twin two Higgs doublet model, a newly proposed model to lift the twin neutrino masses with spontaneous ${\mathbb{Z}}_2$ breaking. The dark photon with a Stueckelberg mass $\mathcal{O}(10)$ MeV ensures the energy in the twin sector as well as the symmetric component of twin sector particles can be depleted. The lightest twin baryons are the dark matter candidates with masses approximately 5.5 GeV, which explain naturally the amount of dark matter and visible matter in the Universe are of the same order. We also demonstrate twin cogenesis in the fraternal twin Higgs setup, in which the dark matter candidate is the twin bottom bound state ${\Omega }_{b^{\prime }{b}^{\prime }{b}^{\prime }}^{\prime }$.

    hep-phastro-ph.COCommun.Theor.Phys.(2023)·23 citations
13. 13*

    Lepton-quark collisions at the Large Hadron Collider

    Luca Buonocore🇨🇭 · Ulrich Haisch🇩🇪 · Paolo Nason🇮🇹 · Francesco Tramontano🇮🇹 · Giulia Zanderighi🇩🇪

    Processes commonly studied at the Large Hadron Collider (LHC) are induced by quarks and gluons inside the protons of the LHC beams. In this letter we demonstrate that, since protons also contain leptons, it is possible to target lepton-induced processes at the LHC as well. In particular, by picking a lepton from one beam and a quark from the other beam, we present for the first time a comprehensive analysis of resonant single leptoquark (LQ) production at a hadron collider. In the case of minimal scalar LQs, we derive novel bounds that arise from the LHC Run II considering all possible flavour combinations of an electron or a muon and an up ($u$), a down ($d$), a strange or a charm quark. For the flavour combinations with a $u$ or a $d$ quark, the obtained limits represent the most stringent constraints to date on LQs of this type. The prospects of our method at future LHC runs are also explored. Given the discovery reach of the proposed LQ signature, we argue that dedicated resonance searches in final states featuring a single light lepton and a single light-flavour jet should be added to the exotics search canon of both the ATLAS and the CMS collaboration.

    hep-phhep-exPRL(2020)·83 citations
14. 14*

    Leptons in the Proton

    Luca Buonocore🇨🇭 · Paolo Nason🇮🇹 · Francesco Tramontano🇮🇹 · Giulia Zanderighi🇩🇪

    As is the case for all light coloured Standard Model particles, also photons and charged leptons appear as constituents in ultrarelativistic hadron beams, and admit a parton density function (PDF). It has been shown recently that the photon PDF can be given in terms of the structure functions and form factors for electron-proton scattering. The same holds for lepton PDFs. In the present work we set up a calculation of the lepton PDFs at next-to-leading order, using the same data input needed in the photon case. A precise knowledge of the lepton densities allows us to study lepton-initiated processes even at a hadron collider, with all possible combinations of same-charge, opposite-charge, same-flavour, different-flavour leptons and leptons-quarks, most of which cannot be realized in any other foreseeable experiment. The lepton densities in the proton are extremely small, so that their contribution to Standard Model processes is generally shadowed by processes initiated by coloured partons. We will show, however, that there are cases where these processes can be relevant, giving rise to rare Standard Model signatures and to new production channels, that can enlarge the discovery potential of New Physics at the LHC and future high energy colliders with hadrons in the initial state.

    hep-phhep-exJHEP(2020)·68 citations
15. 15*

    The Kinetic Heavy Quark Mass to Three Loops

    Matteo Fael🇩🇪 · Kay Schönwald🇩🇪 · Matthias Steinhauser🇩🇪

    We compute three-loop corrections to the relation between the heavy quark masses defined in the pole and kinetic schemes. Using known relations between the pole and $\overline{\mathrm{MS}}$ quark masses we can establish precise relations between the kinetic and $\overline{\mathrm{MS}}$ charm and bottom masses. As compared to two loops, the precision is improved by a factor two to three. Our results constitute important ingredients for the precise determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ at Belle~II.

    hep-phPRL(2020)·52 citations
16. 16*

    A concordance scenario for the observed neutrino from a Tidal Disruption Event

    Walter Winter🇩🇪 · Cecilia Lunardini🇺🇸

    During a tidal disruption event, a star is torn apart by the tidal forces of a supermassive black hole, with about 50% of the star's mass eventually accreted by the black hole. The resulting flare can, in extreme cases of super-Eddington mass accretion, result in a relativistic jet. While tidal disruption events have been theoretically proposed as sources of high-energy cosmic rays and neutrinos, stacking searches indicate that their contribution to the diffuse extragalactic neutrino flux is very low. However, a recent association of a track-like astrophysical neutrino with a tidal disruption event (AT2019dsg) indicates that some tidal disruption events can accelerate cosmic rays to PeV energies. Here we introduce a phenomenological concordance scenario with a relativistic jet to explain this association: an expanding cocoon progressively obscures the X-rays emitted by the accretion disk, while at the same time providing a sufficiently intense external target of back-scattered X-rays for the production of neutrinos via proton-photon interactions. We also reproduce the delay (relative to the peak) of the neutrino emission by scaling the production radius with the black body radius. Our energetics and assumptions for the jet and the cocoon are compatible with expectations from numerical simulations of tidal disruption events.

    ↳ astro-ph.HEhep-phNature Astron.(2021)·74 citations
17. 17*

    Effect of peculiar velocities on the gravitational potential in cosmological models with perfect fluids

    Alvina Burgazli🇺🇦 · Valerii Shulga🇨🇳 · A.Emrah Yükselci🇹🇷 · Alexander Zhuk🇺🇦

    We consider a universe filled with perfect fluid with the constant equation of state parameter $\omega$. In the theory of scalar perturbations, we study the effect of peculiar velocities on the gravitational potential. For radiation with $\omega =1/3$, we obtain the expression for the gravitational potential in the integral form. Numerical calculation clearly demonstrates the modulation of the gravitational potential by acoustic oscillations due to the presence of peculiar velocities. We also show that peculiar velocities affect the gravitational potential in the case of the frustrated network of cosmic strings with $\omega =-1/3$.

    ↳ gr-qcastro-ph.COhep-phhep-thPLB(2020)·3 citations
18. 18*

    ILD Benchmark: Search for Extra Scalars Produced in Association with a $Z$ boson at $\sqrt{s}=500$ GeV

    Yan Wang🇨🇳 · Mikael Berggren🇩🇪 · Jenny List🇩🇪

    We study the prospects for discovering an extra scalar boson $S^0$ at the International Linear Collider (ILC) based on a full simulation of the International Large Detector (ILD). In order to provide results in an as model-independent way as possible, the analysis uses the recoil of the scalar against a $Z$ boson decaying into a pair of muons, $e^{+}{e}^{-}\to \mu \mu S^0$. This process serves as a physics benchmark for the ILD detector performance at $\sqrt{s}=500$ GeV, specifically for the muon ID and momentum resolution, as well as for the identification of initial state radiation photons and their energy measurement. As final results, the sensitivities for discovering the extra scalars at 2 $\sigma$ level are evaluated in terms of a scale factor ${\sin }^2\theta$ with respect to the Standard Model value of the cross section for the Higgs--strahlung process. Two detector models, IDR-L and IDR-S, are considered in the analysis, which differ in radius of the tracking volume, aspect ratio and strength of the magnetic field. While the two detector models show a visible difference in the precision of the reconstructed invariant di-muon mass, no difference is found at the level of the final results.

    ↳ hep-exhep-ph37 citations
19. 19*

    Exploring the partonic phase at finite chemical potential in and out-of equilibrium

    O. Soloveva🇩🇪 · P. Moreau🇺🇸 · L. Oliva🇩🇪 · T. Song🇩🇪 · W. Cassing🇩🇪 · E.Bratkovskaya🇩🇪

    We study the influence of the baryon chemical potential ${\mu }_B$ on the properties of the Quark-Gluon-Plasma (QGP) in and out-of equilibrium. The description of the QGP in equilibrium is based on the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation-of-state of the partonic system above the deconfinement temperature $T_c$ from lattice Quantum Chromodynamics (QCD). We calculate the transport coefficients such as the ratio of shear viscosity $\eta$ and bulk viscosity $\zeta$ over entropy density $s$, i.e., $\eta /s$ and $\zeta /s$ in the $(T,{\mu }_B)$ plane and compare to other model results available at ${\mu }_B=0$. The out-of equilibrium study of the QGP is performed within the Parton-Hadron-String Dynamics (PHSD) transport approach extended in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections (based on the DQPM propagators and couplings) evaluated at the actual temperature $T$ and baryon chemical potential ${\mu }_B$ in each individual space-time cell of the partonic scattering. The traces of their ${\mu }_B$ dependences are investigated in different observables for relativistic heavy-ion collisions with a focus on the directed and elliptic flow coefficients $v_1,v_2$ in the energy range 7.7 GeV $\le \sqrt{s_{NN}}\le 200$ GeV.

    ↳ nucl-thhep-phJ.Phys.Conf.Ser.(2020)·3 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.