Mon·Jul 13, 2020Monday·July 13, 2020

1. 01*

   Anomalies in $B$ Decays and Muon $g-2$ from Dark Loops

   Da Huang🇨🇳 · António P. Morais🇵🇹 · Rui Santos🇵🇹

   We explore a class of models which can provide a common origin for the recently observed evidence for lepton flavor universality violation in $b\to s{l}^{+}{l}^{-}$ decays, the dark matter (DM) problem and the long-standing muon $(g-2)$ anomaly. In particular, both anomalies in the $B$ meson decays and the muon $(g-2)$ can be explained by the additional one-loop diagrams with DM candidates. We first classify several simple models according to the new fields' quantum numbers. We then focus on a specific promising model and perform a detailed study of both DM and flavor physics. A random scan over the relevant parameter space reveals that there is indeed a large parameter space which can explain the three new physics phenomena simultaneously, while satisfying all other flavor and DM constraints. Finally, we discuss some of the possible new physics signatures at the Large Hadron Collider.

   hep-phPRD(2020)·22 citations
2. 02*

   $QQ\bar{s}\bar{s}$ tetraquarks in the chiral quark model

   Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Jorge Segovia🇪🇸

   The low-lying $S$-wave $QQ\bar{s}\bar{s}$ ($Q=c,b$) tetraquark states with $I{J}^P=00^{+}$, $01^{+}$ and $02^{+}$ are systematically investigated in the framework of complex scaling range of chiral quark model. Every structure including meson-meson, diquark-antidiquark and K-type configurations, and all possible color channels in four-body sector are considered by means of a commonly extended variational approach, Gaussian expansion method. Several narrow and wide resonance states are obtained for $cc\bar{s}\bar{s}$ and $bb\bar{s}\bar{s}$ tetraquarks with $I{J}^P=00^{+}$ and $02^{+}$. Meanwhile, narrow resonances for $cb\bar{s}\bar{s}$ tetraquarks are also found in $I{J}^P=00^{+}$, $01^{+}$ and $02^{+}$ states. These results confirm the possibility of finding hadronic molecules with masses $\sim 0.6\text{GeV}$ above the noninteracting hadron-hadron thresholds.

   hep-phhep-exhep-latnucl-ex+1PRD(2020)·36 citations
3. 03*

   Charge Distributions of Moving Nucleons

   Cédric Lorcé (Ecole Polytechnique, CPHT)🇫🇷

   Relativistic charge distributions of targets with arbitrary average momentum are introduced. They provide an interpolation between the usual Breit frame and infinite-momentum frame distributions. We find that Breit frame distributions can be interpreted from a phase-space perspective as internal charge quasi-densities in the rest frame of a localized target, without any relativistic correction. We show also that the apparent discrepancies between Breit frame and infinite-momentum frame distributions simply result from kinematical artifacts associated with spin.

   hep-phnucl-thPRL(2020)·88 citations
4. 04*

   On the nature of near-threshold bound and virtual states

   Inka Matuschek🇩🇪 · Vadim Baru🇩🇪 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪

   Physical states are characterised uniquely by their pole positions and the corresponding residues. Accordingly, in those parameters also the nature of the states should be encoded. For bound states (poles on the real $s$-axis below the lowest threshold on the physical sheet) there is an established criterion formulated originally by Weinberg in the 1960s, which allows one to estimate the amount of compact and molecular components in a given state. We demonstrate in this paper that this criterion can be straightforwardly extended to shallow virtual states (poles on the real $s$-axis below the lowest threshold on the unphysical sheet) which should be classified as molecular. We argue that predominantly non-molecular or compact states exist either as bound states or as resonances (poles on the unphysical sheet off the real energy axis) but not as virtual states. We also discuss the limitations of the mentioned classification scheme.

   hep-phhep-exhep-latnucl-thEPJA(2021)·116 citations
5. 05*

   Absolute neutrino mass as the missing link to the dark sector

   T. de Boer🇩🇪 · M. Klasen🇩🇪 · C. Rodenbeck🇩🇪 · S. Zeinstra🇩🇪

   With the KATRIN experiment, the determination of the absolute neutrino mass scale down to cosmologically favored values has come into reach. We show that this measurement provides the missing link between the Standard Model and the dark sector in scotogenic models, where the suppression of the neutrino masses is economically explained by their only indirect coupling to the Higgs field. We determine the linear relation between the electron neutrino mass and the scalar coupling ${\lambda }_5$ associated with the dark neutral scalar mass splitting to be ${\lambda }_5=3.1\times 10^{-9}{m}_{{\nu }_e}/$eV. This relation then induces correlations among the DM and new scalar masses and their Yukawa couplings. Together, KATRIN and future lepton flavor violation experiments can then probe the fermion DM parameter space, irrespective of the neutrino mass hierarchy and CP phase.

   hep-phastro-ph.COhep-exPRD(2020)·14 citations
6. 06*

   The determination of the spin and parity of a vector-vector system

   Liupan An🇮🇹 · Ronan McNulty🇮🇪 · Mikhail Mikhasenko🇨🇭

   We present a construction of the reaction amplitude for the inclusive production of a resonance decaying to a pair of identical vector particles such as $J/\psi J/\psi$, $\rho \rho$, $\varphi \varphi$. The method provides the possibility of determining the spin and parity of a resonance in a model-independent way. The methodology is demonstrated using the Standard Model decay of the Higgs boson to four leptons and through angular correlations in the production and decays of $J/\psi$ pairs.

   hep-phJHEP(2024)·8 citations
7. 07*

   An Active-to-Sterile Neutrino Transition Dipole Moment and the XENON1T Excess

   Ian M. Shoemaker🇺🇸 · Yu-Dai Tsai🇺🇸 · Jason Wyenberg🇺🇸

   In this short letter, we find that a magnetic transition dipole moment between tau and sterile neutrinos can account for the XENON1T excess events. Unlike the ordinary neutrino dipole moment, the introduction of the new sterile mass scale allows for astrophysical bounds to be suppressed. Interestingly, the best-fit regions that are compatible with the SN1987A imply either boron-8 or CNO neutrinos as the source flux. We find that sterile neutrinos of either $\sim$ 260 keV or in the $\sim$(500 - 800) keV mass range are capable of evading astrophysical constraints while being able to successfully explain the XENON1T event rate. The sterile neutrino in the best fit parameter space may have significant effects on big bang nucleosynthesis (BBN). We show the region in which a low reheating temperature of the Universe may allow the BBN constraints to be alleviated.

   hep-phastro-ph.COPRD(2021)·62 citations
8. 08*

   On the Origin of Long-Lived Particles

   Jared Barron🇨🇦 · David Curtin🇨🇦

   MATHUSLA is a proposed large-volume displaced vertex (DV) detector, situated on the surface above CMS and designed to search for long-lived particles (LLPs) produced at the HL-LHC. We show that a discovery of LLPs at MATHUSLA would not only prove the existence of BSM physics, it would also uncover the theoretical origin of the LLPs, despite the fact that MATHUSLA gathers no energy or momentum information on the LLP decay products. Our analysis is simple and robust, making it easily generalizable to include more complex LLP scenarios, and our methods are applicable to LLP decays discovered in ATLAS, CMS, LHCb, or other external detectors. In the event of an LLP detection, MATHUSLA can act as a Level-1 trigger for the main detector, guaranteeing that the LLP production event is read out at CMS. We perform an LLP simplified model analysis to show that combining information from the MATHUSLA and CMS detectors would allow the LLP production mode topology to be determined with as few as $\sim 100$ observed LLP decays. Underlying theory parameters, like the LLP and parent particle masses, can also be measured with $\lesssim 10\%$ precision. Together with information on the LLP decay mode from the geometric properties of the observed DV, it is clear that MATHUSLA and CMS together will be able to characterize any newly discovered physics in great detail.

   hep-phhep-exJHEP(2020)·13 citations
9. 09*

   Quarkonium TMD fragmentation functions in NRQCD

   Miguel G. Echevarria🇪🇸 · Yiannis Makris🇮🇹 · Ignazio Scimemi🇪🇸

   We study the transverse-momentum spectrum of quarkonium production from single light-parton fragmentation mechanism. In the case of semi-inclusive deep inelastic scattering, we observe that there are two possible initiating processes, namely photon-gluon fusion and light-quark fragmentation. For the second case we derive the factorization theorem, which involves a new hadronic quantity: the quarkonium transverse-momentum-dependent fragmentation functions in NRQCD. We calculate their matching onto the non-perturbative long distance matrix elements at the lowest order in the strong-coupling constant ($\mathcal{O}({\alpha }_s^2)$). Focusing on the case of the electron-ion collider, we make a comparative phenomenological study of the two production mechanisms and find the regions of the phase space where one is dominant over the other.

   hep-phJHEP(2020)·30 citations
10. 10*

    Improved quark coalescence model for spin alignment and polarization of hadrons

    Xin-Li Sheng🇨🇳 · Qun Wang🇨🇳 · Xin-Nian Wang🇨🇳

    We propose an improved quark coalescence model for spin alignment of vector mesons and polarization of baryons by spin density matrix with phase space dependence. The spin density matrix is defined through Wigner functions. Within the model we propose an understanding of spin alignments of vector mesons $\varphi$ and $K^{\ast 0}$ (including ${\bar{K}}^{\ast 0}$) in the static limit: a large positive deviation of ${\rho }_{00}$ for $\varphi$ mesons from 1/3 may come from the electric part of the vector $\varphi$ field, while a negative deviation of ${\rho }_{00}$ for $K^{\ast 0}$ may come from the electric part of vorticity tensor fields. Such a negative contribution to ${\rho }_{00}$ for $K^{\ast 0}$ mesons, in comparison with the same contribution to ${\rho }_{00}$ for $\varphi$ mesons which is less important, is amplified by a factor of the mass ratio of strange to light quark times the ratio of $⟨{\mathbf{p}}_b^2⟩$ on the wave function of $K^{\ast 0}$ to $\varphi$ (${\mathbf{p}}_b$ is the relative momentum of two constituent quarks of $K^{\ast 0}$ and $\varphi$). These results should be tested by a detailed and comprehensive simulation of vorticity tensor fields and vector meson fields in heavy ion collisions.

    ↳ nucl-thhep-phPRD(2020)·87 citations
11. 11*

    Gravitational-wave detectors as particle-physics laboratories: Constraining scalar interactions with a coherent inspiral model of boson-star binaries

    Costantino Pacilio🇮🇹 · Massimo Vaglio🇮🇹 · Andrea Maselli🇮🇹 · Paolo Pani🇮🇹

    Gravitational-wave (GW) detections of binary neutron star coalescences play a crucial role to constrain the microscopic interaction of matter at ultrahigh density. Similarly, if boson stars exist in the universe their coalescence can be used to constrain the fundamental coupling constants of a scalar field theory. We develop the first coherent waveform model for the inspiral of boson stars with quartic interactions. The waveform includes coherently spin-induced quadrupolar and tidal-deformability contributions in terms of the masses and spins of the binary and of a single coupling constant of the theory. We show that future instruments such as the Einstein Telescope and the Laser Interferometer Space Antenna can provide strong complementary bounds on bosonic self-interactions, while the constraining power of current detectors is marginal.

    ↳ gr-qcastro-ph.HEhep-phPRD(2020)·49 citations
12. 12*

    Global fits of axion-like particles to XENON1T and astrophysical data

    Peter Athron🇦🇺 · Csaba Balázs🇦🇺 · Ankit Beniwal🇧🇪 · J. Eliel Camargo-Molina🇬🇧 · Andrew Fowlie🇦🇺 · Tomás E. Gonzalo🇦🇺 · Sebastian Hoof🇩🇪 · Felix Kahlhoefer🇩🇪 · David J. E. Marsh🇩🇪 · Markus Tobias Prim🇩🇪 · Andre Scaffidi🇮🇹 · Pat Scott🇬🇧 and 4 other authors

    The excess of electron recoil events seen by the XENON1T experiment has been interpreted as a potential signal of axion-like particles (ALPs), either produced in the Sun, or constituting part of the dark matter halo of the Milky Way. It has also been explained as a consequence of trace amounts of tritium in the experiment. We consider the evidence for the solar and dark-matter ALP hypotheses from the combination of XENON1T data and multiple astrophysical probes, including horizontal branch stars, red giants, and white dwarfs. We briefly address the influence of ALP decays and supernova cooling. While the different datasets are in clear tension for the case of solar ALPs, all measurements can be simultaneously accommodated for the case of a sub-dominant fraction of dark-matter ALPs. Nevertheless, this solution requires the tuning of several a priori unknown parameters, such that for our choices of priors a Bayesian analysis shows no strong preference for the ALP interpretation of the XENON1T excess over the background hypothesis.

    ↳ astro-ph.COhep-phJHEP(2021)·66 citations
13. 13*

    Hydrodynamic gradient expansion in linear response theory

    Michal P. Heller🇩🇪 · Alexandre Serantes🇫🇮 · Michał Spaliński🇵🇱 · Viktor Svensson🇩🇪 · Benjamin Withers🇬🇧

    A foundational question in relativistic fluid mechanics concerns the properties of the hydrodynamic gradient expansion at large orders. We establish the precise conditions under which this gradient expansion diverges for a broad class of microscopic theories admitting a relativistic hydrodynamic limit, in the linear regime. Our result does not rely on highly symmetric fluid flows utilized by previous studies of heavy-ion collisions and cosmology. The hydrodynamic gradient expansion diverges whenever energy density or velocity fields have support in momentum space exceeding a critical momentum, and converges otherwise. This critical momentum is an intrinsic property of the microscopic theory and is set by branch point singularities of hydrodynamic dispersion relations.

    ↳ hep-thhep-phnucl-thphysics.flu-dynPRD(2021)·61 citations
14. 14*

    Is negative kinetic energy meta-stable?

    Christian Gross🇮🇹 · Alessandro Strumia🇮🇹 · Daniele Teresi🇮🇹 · Matteo Zirilli🇮🇹

    We explore the possibility that theories with negative kinetic energy (ghosts) can be meta-stable up to cosmologically long times. In classical mechanics, ghosts undergo spontaneous lockdown rather than run-away if weakly-coupled and non-resonant. Physical examples of this phenomenon are shown. In quantum mechanics this leads to meta-stability similar to vacuum decay. In classical field theory, lockdown is broken by resonances and ghosts behave statistically, drifting towards infinite entropy as no thermal equilibrium exists. We analytically and numerically compute the run-away rate finding that it is cosmologically slow in 4-derivative gravity, where ghosts have gravitational interactions only. In quantum field theory the ghost run-away rate is naively infinite in perturbation theory, analogously to what found in early attempts to compute vacuum tunnelling; we do not know the true rate.

    ↳ hep-thcond-mat.stat-mechgr-qchep-ph+1PRD(2021)·34 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.