Mon·Jan 6, 2020Monday·January 6, 2020

1. 01*

   Real-time chiral dynamics from a digital quantum simulation

   Dmitri E. Kharzeev🇺🇸 · Yuta Kikuchi🇺🇸

   The chiral magnetic effect in a strong magnetic field can be described using the chiral anomaly in the $(1+1)$-dimensional massive Schwinger model with a time-dependent $\theta$-term. We perform a digital quantum simulation of the model at finite $\theta$-angle and vanishing gauge coupling using an IBM-Q digital quantum simulator, and observe the corresponding vector current induced in a system of relativistic fermions by a global {\it chiral quench} -- a sudden change in the chiral chemical potential or $\theta$-angle. At finite fermion mass, there appears an additional contribution to this current that stems from the non-anomalous relaxation of chirality. Our results are relevant for the real-time dynamics of chiral magnetic effect in heavy ion collisions and in chiral materials, as well as for modeling high-energy processes at hadron colliders.

   hep-phhep-latquant-phPRResearch(2020)·102 citations
2. 02*

   Suppressed flavor violation in Lepton Flavored Dark Matter from an extra dimension

   Niral Desai🇺🇸 · Can Kilic🇺🇸 · Yuan-Pao Yang🇺🇸 · Taewook Youn🇺🇸

   Phenomenological studies of Flavored Dark Matter (FDM) models often have to assume a near-diagonal flavor structure in the coupling matrix in order to remain consistent with bounds from flavor violating processes. In this paper we show that for Lepton FDM, such a structure can naturally arise from an extra dimensional setup. The extra dimension is taken to be flat, with the dark matter and mediator fields confined to a brane on one end of the extra dimension, and the Higgs field to a brane on the other end. The Standard Model fermion and gauge fields are the zero modes of corresponding bulk fields with appropriate boundary conditions. Global flavor symmetries exist in the bulk and on the FDM brane, while they are broken on the Higgs brane. Flavor violating processes arise due to the misalignment of bases for which the interactions on the two branes are diagonalized, and their size can be controlled by a choice of the lepton profiles along the extra dimension. By studying the parameter space for the model, we show that when relic abundance and indirect detection constraints are satisfied, the rates for flavor violating processes such as $\mu \to e\gamma$ remain far below the experimental limits.

   hep-phPRD(2020)·12 citations
3. 03*

   Exploratory study of the coupled-channel scattering in finite volume and the $Z_c(3900)$ resonance

   Mei-Zhu Yan🇨🇳 · Dan Zhou🇨🇳 · Zhi-Hui Guo🇨🇳

   In this note we first introduce the theoretical formalism of the unitarization of the two-body scattering both in the infinite and finite volumes. Then we apply this formalism to the study of the $Z_c(3900)$ resonance in the $J/\psi \pi$ and $D{\bar{D}}^{\ast }$ coupled-channel scattering. The recent lattice finite-volume spectra are confronted with our predictions.

   hep-ph0 citations
4. 04*

   Photoproduction of three jets in the CGC: gluon TMDs and dilute limit

   Tolga Altinoluk🇵🇱 · Renaud Boussarie🇺🇸 · Cyrille Marquet🇫🇷 · Pieter Taels🇫🇷

   We study the process $\gamma A\to q\bar{q}g+X$ in the Color Glass Condensate (CGC) effective theory. After obtaining the cross section, we consider two kinematic limits which are encompassed in our result. In the so-called correlation limit, the vector sum of the transverse momenta of the three outgoing particles is small with respect to the individual transverse momenta; the cross section then simplifies considerably and can be written in a factorized form, sensitive to both the unpolarized and linearly-polarized Weizsäcker-Williams transverse momentum dependent gluon distribution function (gluon TMD). The second limit of the CGC cross section that we consider is the dilute limit, which we obtain after performing a weak-field expansion; we recover a typical linear-regime expression, involving a single unintegrated gluon distribution function. Using numerical simulations of the small-$x$ QCD evolution of the TMDs, we investigate the rapidity dependence of the cross section in the correlation limit.

   hep-phJHEP(2020)·48 citations
5. 05*

   On renormalons of static QCD potential at $u=1/2$ and $3/2$

   Yukinari Sumino🇯🇵 · Hiromasa Takaura🇯🇵

   We investigate the $u=1/2$ [$\mathcal{O}({\Lambda }_{\mathrm{QCD}})$] and $u=3/2$ [$\mathcal{O}({\Lambda }_{\mathrm{QCD}}^3)$] renormalons in the static QCD potential in position space and momentum space using the OPE of the potential-NRQCD effective field theory. This is an old problem and we provide a formal formulation to analyze it. In particular we present detailed examinations of the $u=3/2$ renormalons. We clarify how the $u=3/2$ renormalon is suppressed in the momentum-space potential in relation with the Wilson coefficient $V_A(r)$. We also point out that it is not straightforward to subtract the IR renormalon and IR divergences simultaneously in the multipole expansion. Numerical analyses are given, which clarify the current status of our knowledge on the perturbative series. The analysis gives a positive reasoning to the method for subtracting renormalons used in recent ${\alpha }_s(M_Z)$ determination from the QCD potential.

   hep-phJHEP(2020)·13 citations
6. 06*

   Double parton distributions of the pion in the NJL model

   Wojciech Broniowski🇵🇱 · Enrique Ruiz Arriola🇪🇸

   We evaluate the valence double parton distribution (dPDF) of the pion in the Nambu--Jona-Lasinio model. At the low-energy quark-model scale and in the chiral limit a particularly simple factorized form $D(x_1,x_2,\vec{q})=\delta (1-x_1-x_2)F(\vec{q})$ follows, where $x_{1,2}$ denote the longitudinal momentum fractions of the valence quark and antiquark, and $\vec{q}$ is their relative transverse momentum. For $\vec{q}=\vec{0}$ our result complies to the Gaunt-Sterling sum rules. We carry out the necessary dDGLAP evolution to higher scales via the Mellin moments and explore its impact on the correlation defined as the ratio of dPDF to the product of single parton distributions, $D(x_1,x_2,\vec{q}=\vec{0})/D(x_1)D(x_2)$. Since the ratios of the valence Mellin moments $⟨x_1^n{x}_2^m⟩/⟨x_1^n⟩⟨x_2^m⟩$ are invariants of the dDGLAP evolution, they may serve as robust measures of these correlations. Model predictions, which can be tested in the upcoming lattice simulations, are provided. We also discuss the transverse form factor related to the dPDF of the pion.

   hep-phhep-latPoS(2020)·5 citations
7. 07*

   Constraining the gauge and scalar sectors of the doublet left-right symmetric model

   Véronique Bernard🇫🇷 · Sébastien Descotes-Genon🇫🇷 · Luiz Vale Silva🇪🇸

   We consider a left-right symmetric extension of the Standard Model where the spontaneous breakdown of the left-right symmetry is triggered by doublets. The electroweak $\rho$ parameter is protected from large corrections in this Doublet Left-Right Model (DLRM), contrary to the triplet case. This allows in principle for more diverse patterns of symmetry breaking. We consider several constraints on the gauge and scalar sectors of DLRM: the unitarity of scattering processes involving gauge bosons with longitudinal polarisations, the radiative corrections to the muon $\Delta r$ parameter and the electroweak precision observables measured at the $Z$ pole and at low energies. Combining these constraints within the frequentist CKMfitter approach, we see that the fit pushes the scale of left-right symmetry breaking up to a few TeV, while favouring an electroweak symmetry breaking triggered not only by the $SU(2{)}_L\times SU(2{)}_R$ bi-doublet, which is the case most commonly considered in the literature, but also by the $SU(2{)}_L$ doublet.

   hep-phJHEP(2020)·18 citations
8. 08*

   Low-energy theorem for $\gamma \to 3\pi$: surface terms against $\pi a_1$-mixing

   A. A. Osipov🇷🇺 · M. M. Khalifa🇷🇺 · B. Hiller🇵🇹

   We reconsider the contribution due to $\pi a_1$-mixing to the anomalous $\gamma \to {\pi }^{+}{\pi }^0{\pi }^{-}$ amplitude from the standpoint of the low-energy theorem $F^{\pi }=e{f}_{\pi }^2{F}^{3\pi }$, which relates the electromagnetic form factor $F_{{\pi }^0\to \gamma \gamma }=F^{\pi }$ with the form factor $F_{\gamma \to {\pi }^{+}{\pi }^0{\pi }^{-}}=F^{3\pi }$ both taken at vanishing momenta of mesons. Our approach is based on a recently proposed covariant diagonalization of $\pi a_1$-mixing within a standard effective QCD-inspired meson Lagrangian obtained in the framework of the Nambu-Jona-Lasinio model. We show that the two surface terms appearing in the calculation of the anomalous triangle quark diagrams or AVV- and AAA-type amplitudes are uniquely fixed by this theorem. As a result, both form factors $F^{\pi }$ and $F^{3\pi }$ are not affected by the $\pi a_1$-mixing, but the concept of vector meson dominance (VMD) fails for $\gamma \to {\pi }^{+}{\pi }^0{\pi }^{-}$.

   hep-phPRD(2020)·6 citations
9. 09*

   Speeding Up Dark Matter With Solar Neutrinos

   Yue Zhang🇨🇦

   We present a novel mechanism of using solar neutrinos to speed up dark matter, inspired by the fact that neutrinos are the most energetic particles from the Sun with a well-understood spectrum. In a neutrino portal dark sector model, we show that dark matter with sub-GeV mass could be accelerated by the $pp$ neutrinos to velocities well above $10^{-3}c$ and capable of depositing large enough energy at direct detection experiments. A crucial ingredient of this mechanism is the dissociation of stable dark matter bound states that exist in Nature. The resulting dark matter velocity distribution bears a strong resemblance in shape to the solar neutrino spectrum. As an application, we derive a leading limit on light dark matter interaction by reinterpreting a recent PICO experiment result.

   hep-phastro-ph.SRhep-exPTEP(2022)·36 citations
10. 10*

    Search for Dark Matter in Upsilon Decays at BABAR Experiment

    Romulus Godang🇺🇸

    Recent investigations have suggested that the singlet six-quark combination $uuddss$ may be a deeply bound state $S$, called Sexaquark. An essentially stable state $S$ is a potentially excellent Dark Matter candidate. We present the first search for a stable, doubly strange six-quark state in the decays of ${\rm Y}(4S)\to \Lambda \bar{\Lambda }$. Based on a data sample of ${\rm Y}(2S)$ and ${\rm Y}(3S)$ decays collected by the BABAR Experiment we report the most recent results and set stringent limits on the existence of such exotic particle.

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2020)·0 citations
11. 11*

    Nonsingular Ekpyrotic Cosmology with a Nearly Scale-Invariant Spectrum of Cosmological Perturbations and Gravitational Waves

    Robert Brandenberger🇨🇦 · Ziwei Wang (McGill University)🇨🇦

    We propose a mechanism borrowed from string theory which yields a non-singular transition from a phase of Ekpyrotic contraction to the expanding phase of Standard Big Bang cosmology. The same mechanism converts the initial vacuum spectrum of cosmological fluctuations before the bounce into a scale-invariant one, and also changes the spectrum of gravitational waves into an almost scale-invariant one. The scalar and tensor tilts are predicted to be the same, in contrast to the predictions from the "String Gas Cosmology" scenario. The amplitude of the gravitational wave spectrum depends on the ratio of the string scale to the Planck scale and may be in reach of upcoming experiments.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2020)·52 citations
12. 12*

    Evidence against Ryskin's model of cosmic acceleration

    Joseph Ryan🇺🇸

    In this paper I examine how well Ryskin's model of emergent cosmic acceleration fits several sets of cosmological observations. I find that while Ryskin's model is somewhat compatible with the standard model of cosmological acceleration ($\Lambda$CDM) for low redshift (z < 1) measurements, its predictions diverge considerably from those of the standard model for measurements made at high redshift (for which z > 1), and it is therefore not a compelling substitute for the standard model.

    ↳ astro-ph.COgr-qchep-phAstropart.Phys.(2020)·2 citations
13. 13*

    First observation of excited ${\Omega }_b^{-}$ states

    LHCb collaboration: R. Aaij🇳🇱 · C. Abellán Beteta🇨🇭 · T. Ackernley🇬🇧 · B. Adeva🇪🇸 · M. Adinolfi🇬🇧 · H. Afsharnia🇫🇷 · C.A. Aidala🇺🇸 · S. Aiola🇮🇹 · Z. Ajaltouni🇫🇷 · S. Akar🇺🇸 · P. Albicocco🇮🇹 · J. Albrecht🇩🇪 and 895 other authors

    We report four narrow peaks in the ${\Xi }_b^0{K}^{-}$ mass spectrum obtained using $pp$ collisions at center-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb${}^{-1}$ recorded by the LHCb experiment. Referring to these states by their mass, the mass values are \begin{align*} m(\Omega_b(6316)^-) &= 6315.64\pm0.31\pm0.07\pm0.50 {\rm MeV}, \\ m(\Omega_b(6330)^-) &= 6330.30\pm0.28\pm0.07\pm0.50 {\rm MeV}, \\ m(\Omega_b(6340)^-) &= 6339.71\pm0.26\pm0.05\pm0.50 {\rm MeV}, \\ m(\Omega_b(6350)^-) &= 6349.88\pm0.35\pm0.05\pm0.50 {\rm MeV}, \end{align*}where the uncertainties are statistical, systematic and the last is due to the knowledge of the ${\Xi }_b^0$ mass. The natural widths of the three lower mass states are consistent with zero, and the 90% confidence-level upper limits are determined to be $\Gamma ({\Omega }_b(6316{)}^{-})<2.8$ MeV, $\Gamma ({\Omega }_b(6330{)}^{-})<3.1$ MeV and $\Gamma ({\Omega }_b(6340{)}^{-})<1.5$ MeV. The natural width of the ${\Omega }_b(6350{)}^{-}$ peak is $1.4_{-0.8}^{+1.0}\pm 0.1$ MeV, which is 2.5$\sigma$ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6$\sigma$ to 7.2$\sigma$. After accounting for the look-elsewhere effect, the significances of the ${\Omega }_b(6316{)}^{-}$ and ${\Omega }_b(6330{)}^{-}$ peaks are reduced to 2.1$\sigma$ and 2.6$\sigma$ respectively, while the two higher mass peaks exceed 5$\sigma$. The observed peaks are consistent with expectations for excited ${\Omega }_b^{-}$ resonances.

    ↳ hep-exhep-phPRL(2020)·117 citations
14. 14*

    Off-shell Ward identities for N-gluon amplitudes

    Naser Ahmadiniaz🇩🇪 · Christian Schubert🇲🇽

    Off-shell Ward identities in non-abelian gauge theory continue to be a subject of active research, since they are, in general, inhomogeneous and their form depends on the chosen gauge-fixing procedure. For the three-gluon and four-gluon vertices, it is known that a relatively simple form of the Ward identity can be achieved using the pinch technique or, equivalently, the background-field method with quantum Feynman gauge. The latter is also the gauge-fixing underlying the string-inspired formalism, and here we use this formalism to derive the corresponding form of the Ward identity for the one-loop N - gluon amplitudes.

    ↳ hep-thhep-phEPL(2020)·10 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.