Mon·Nov 4, 2019Monday·November 4, 2019

1. 01*

   $\gamma N\to N^{\ast }(1535)$ transition in soft-wall AdS/QCD

   Thomas Gutsche🇩🇪 · Valery E. Lyubovitskij🇩🇪 · Ivan Schmidt🇨🇱

   We present a study of the $N^{\ast }(1535)$ resonance electroexcitation in a soft-wall AdS/QCD model. Both the transverse $A_{1/2}^p$ and longitudinal $S_{1/2}^p$ helicity amplitudes are calculated resulting in good agreement with data and with the MAID parametrization.

   hep-phPRD(2020)·16 citations
2. 02*

   Nonstandard neutrino interactions and mu-tau reflection symmetry

   Jiajun Liao🇨🇳 · Newton Nath🇨🇳 · TseChun Wang🇨🇳 · Ye-Ling Zhou🇬🇧

   Nonstandard interactions (NSIs), possible subleading effects originating from new physics beyond the Standard Model, may affect the propagation of neutrinos and eventually contribute to measurements of neutrino oscillations. Besides this, $\mu -\tau$ reflection symmetry, naturally predicted by non-Abelian discrete flavor symmetries, has been very successful in explaining the observed leptonic mixing patterns. In this work, we study the combined effect of both. We present an $S_4$ flavor model with $\mu -\tau$ reflection symmetry realized in both neutrino masses and NSIs. Under this formalism, we perform a detailed study for the upcoming neutrino experiments DUNE and T2HK. Our simulation results show that under the $\mu -\tau$ reflection symmetry, NSI parameters are further constrained and the mass ordering sensitivity is less affected by the presence of NSIs.

   hep-phPRD(2020)·15 citations
3. 03*

   Doubly-heavy tetraquarks

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

   In the framework of the chiral quark model along with complex scaling range, we perform a dynamical study on the low-lying $S$-wave doubly-heavy tetraquark states ($QQ\bar{q}\bar{q}$, $Q=c,b$ and $q=u,d$) with an accurate computing approach, Gaussian expansion method. The meson-meson and diquark-antidiquark configurations within all possible color structures for spin-parity quantum numbers $J^P=0^{+}$, $1^{+}$ and $2^{+}$, and in the $0$ and $1$ isospin sectors are considered. Possible tightly bound and narrow resonance states are obtained for doubly-charm and doubly-bottom tetraquarks with $I{J}^P=01^{+}$, and these exotic states are also obtained in charm-bottom tetraquarks with $00^{+}$ and $01^{+}$ quantum numbers. Only loosely bound state is found in charm-bottom tetraquarks of $02^{+}$ states. All of these bound states within meson-meson configurations are loosely bound whether in color-singlet channels or coupling to hidden-color ones. However compact structures are available in diquark-antidiquark channels except for charm-bottom tetraquarks in $02^{+}$ states.

   hep-phPRD(2020)·95 citations
4. 04*

   Impact parameter dependence of the azimuthal asymmetry in lepton pair production in heavy ion collisions

   Cong Li🇨🇳 · Jian Zhou🇨🇳 · Ya-jin Zhou🇨🇳

   We investigate the impact parameter dependence of the $\cos 4\varphi$ azimuthal asymmetry for electromagnetic lepton pair production in heavy ion collisions. The asymmetry induced by linearly polarized coherent photons exhibits strong impact parameter dependence.

   hep-phPRD(2020)·83 citations
5. 05*

   Prospects for Finding Sterile Neutrino Dark Matter at KATRIN

   Cristina Benso🇩🇪 · Vedran Brdar🇩🇪 · Manfred Lindner🇩🇪 · Werner Rodejohann🇩🇪

   We discuss under what circumstances a signal in upcoming laboratory searches for keV-scale sterile neutrinos would be compatible with those particles being a sizable part or all of dark matter. In the parameter space that will be experimentally accessible by KATRIN/TRISTAN, strong X-ray limits need to be relaxed and dark matter overproduction needs to be avoided. We discuss postponing the dark matter production to lower temperatures, a reduced sterile neutrino contribution to dark matter, and a reduction of the branching ratio in photons and active neutrinos through cancellation with a new physics diagram. Both the Dodelson-Widrow and the Shi-Fuller mechanisms for sterile neutrino dark matter production are considered. As a final exotic example, potential consequences of CPT violation are discussed.

   hep-phastro-ph.COPRD(2019)·37 citations
6. 06*

   The $g-2$ of charged leptons, $\alpha (M_Z^2)$ and the hyperfine splitting of muonium

   Alexander Keshavarzi🇬🇧 · Daisuke Nomura🇯🇵 · Thomas Teubner🇬🇧

   Following updates in the compilation of $e^{+}{e}^{-}\to \mathrm{hadrons}$ data, this work presents re-evaluations of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the electron ($a_e$), muon ($a_{\mu }$) and tau lepton ($a_{\tau }$), to the ground-state hyperfine splitting of muonium and also updates the hadronic contributions to the running of the QED coupling at the mass scale of the $Z$ boson, $\alpha (M_Z^2)$. Combining the results for the hadronic vacuum polarisation contributions with recent updates for the hadronic light-by-light corrections, the electromagnetic and the weak contributions, the deviation between the measured value of $a_{\mu }$ and its Standard Model prediction amounts to $\Delta a_{\mu }=(28.02\pm 7.37)\times 10^{-10}$, corresponding to a muon $g-2$ discrepancy of $3.8\sigma$.

   hep-phhep-exPRD(2020)·681 citations
7. 07*

   Dynamical grooming of QCD jets

   Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Konrad Tywoniuk🇳🇴

   We propose a new class of infrared-collinear (IRC) and Sudakov safe observables with an associated jet grooming technique that removes dynamically soft and large angle branches. It is based on identifying the hardest branch in the Cambridge/Aachen re-clustering sequence and discarding prior splittings that occur at larger angles. This leads to a dynamically generated cut-off on the phase space of the tagged splitting that is encoded in a Sudakov form factor. In this exploratory study we focus on the mass and momentum sharing distributions of the tagged splitting which we analyze analytically to modified leading logarithmic accuracy and compare to Monte-Carlo simulations.

   hep-phhep-exnucl-exnucl-thPRD(2020)·66 citations
8. 08*

   NNLO QCD corrections to three-photon production at the LHC

   Herschel A. Chawdhry🇬🇧 · Michał Czakon🇩🇪 · Alexander Mitov🇬🇧 · Rene Poncelet🇬🇧

   We compute the NNLO QCD corrections to three-photon production at the LHC. This is the first NNLO QCD calculation for a $2\to 3$ process. Our calculation is exact, except for the scale-independent part of the two-loop finite remainder which is included in the leading color approximation. We estimate the size of the missing two-loop corrections and find them to be phenomenologically negligible. We compare our predictions with available 8 TeV measurement from the ATLAS collaboration. We find that the inclusion of the NNLO corrections eliminates the existing significant discrepancy with respect to NLO QCD predictions, paving the way for precision phenomenology in this process.

   hep-phhep-exhep-thJHEP(2020)·152 citations
9. 09*

   Decay properties of the $X(3872)$ through the Fierz rearrangement

   Hua-Xing Chen🇨🇳

   We systematically construct all the tetraquark currents of $J^{PC}=1^{++}$ with the quark configurations $[cq][\bar{c}\bar{q}]$, $[\bar{c}q][\bar{q}c]$, and $[\bar{c}c][\bar{q}q]$ ($q=u/d$). Their relations are derived using the Fierz rearrangement of the Dirac and color indices, through which we study decay properties of the $X(3872)$ under both the compact tetraquark and hadronic molecule interpretations. We propose to search for the $X(3872)\to {\chi }_{c0}\pi$, ${\eta }_c\pi \pi$, and ${\chi }_{c1}\pi \pi$ decay processes in particle experiments.

   hep-phhep-exhep-latCommun.Theor.Phys.(2022)·12 citations
10. 10*

    Radius of convergence in lattice QCD at finite ${\mu }_B$ with rooted staggered fermions

    Matteo Giordano🇭🇺 · Kornel Kapas🇭🇺 · Sandor D. Katz🇭🇺 · Daniel Nogradi🇭🇺 · Attila Pasztor🇭🇺

    In typical statistical mechanical systems the grand canonical partition function at finite volume is proportional to a polynomial of the fugacity $e^{\mu /T}$. The zero of this Lee-Yang polynomial closest to the origin determines the radius of convergence of the Taylor expansion of the pressure around $\mu =0$. The computationally cheapest formulation of lattice QCD, rooted staggered fermions, with the usual definition of the rooted determinant, does not admit such a Lee-Yang polynomial. We argue that the radius of convergence is then bounded by the spectral gap of the reduced matrix of the unrooted staggered operator. This is a cutoff effect that potentially affects all estimates of the radius of convergence with the standard staggered rooting. We suggest a new definition of the rooted staggered determinant at finite chemical potential that allows for a definition of a Lee-Yang polynomial, and, therefore of the numerical study of Lee-Yang zeros. We also describe an algorithm to determine the Lee-Yang zeros and apply it to configurations generated with the 2-stout improved staggered action at $N_t=4$. We perform a finite-volume scaling study of the leading Lee-Yang zeros and estimate the radius of convergence of the Taylor expansion extrapolated to an infinite volume. We show that the limiting singularity is not on the real line, thus giving a lower bound on the location of any possible phase transitions at this lattice spacing. In the vicinity of the crossover temperature at zero chemical potential, the radius of convergence turns out to be ${\mu }_B/T\approx 2$ and roughly temperature independent. Our simulations are performed at strange quark chemical potential ${\mu }_s=0$, but the method can be straightforwardly extended to strangeness chemical potential ${\mu }_S=0$ or strangeness neutrality.

    ↳ hep-lathep-phnucl-thPRD(2020)·50 citations
11. 11*

    Primordial Black Holes from a tiny bump/dip in the Inflaton potential

    Swagat S. Mishra🇮🇳 · Varun Sahni🇮🇳

    Scalar perturbations during inflation can be substantially amplified by tiny features in the inflaton potential. A bump-like feature behaves like a local speed-breaker and lowers the speed of the scalar field, thereby locally enhancing the scalar power spectrum. A bump-like feature emerges naturally if the base inflaton potential $V_b(\varphi )$ contains a local correction term such as $V_b(\varphi )\left[1+\epsilon (\varphi )\right]$ at $\varphi ={\varphi }_0$. The presence of such a localised correction term at ${\varphi }_0$ leads to a large peak in the curvature power spectrum and to an enhanced probability of black hole formation. Remarkably this does not significantly affect the scalar spectral index $n_{{}_S}$ and tensor to scalar ratio $r$ on CMB scales. Consequently such models can produce higher mass primordial black holes ($M_{\mathrm{PBH}}\ge 1M_{\odot }$) in contrast to models with `near inflection-point potentials' in which generating higher mass black holes severely affects $n_{{}_S}$ and $r$. With a suitable choice of the base potential - such as the string theory based (KKLT) inflation or the $\alpha$-attractor models - the amplification of primordial scalar power spectrum can be as large as $10^7$ which leads to a significant contribution of primordial black holes (PBHs) to the dark matter density today, $f_{\mathrm{PBH}}={\Omega }_{0,\mathrm{PBH}}/{\Omega }_{0,\mathrm{DM}}\sim O(1)$. Interestingly, our results remain valid if the bump is replaced by a dip. In this case the base inflaton potential $V_b(\varphi )$ contains a negative local correction term such as $V_b(\varphi )\left[1-\epsilon (\varphi )\right]$ at $\varphi ={\varphi }_0$ which leads to an enhanced probability of PBH formation. We conclude that primordial black holes in the mass range $10^{-17}{M}_{\odot }\le M_{\mathrm{PBH}}\le 100M_{\odot }$ can easily form in single field inflation in the presence of small bump-like and dip-like features in the inflaton potential.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2020)·211 citations
12. 12*

    O$(d,d)$ covariant String Cosmology to all orders in ${\alpha }^{\prime }$

    Heliudson Bernardo🇨🇦 · Robert Brandenberger🇨🇦 · Guilherme Franzmann🇸🇪

    Recently, all duality invariant ${\alpha }^{\prime }$-corrections to the massless NS-NS sector of string theory on time-dependent backgrounds were classified and the form of their contribution to the action were calculated. In this paper we introduce matter sources in the resulting equations of motion in an O$(d,d)$ covariant way. We show that either starting with the corrected equations and sourcing them with matter or considering corrections to the matter sourced lowest order equations give the same set of equations that defines string cosmology to all orders in ${\alpha }^{\prime }$. We also discuss perturbative and non-perturbative de Sitter solutions including matter.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2020)·55 citations
13. 13*

    String Gases and the Swampland

    Samuel Laliberte🇨🇦 · Robert Brandenberger🇨🇦

    In this paper, we study some aspects of moduli stabilization using string gases in the context of the Swampland. In the framework which we derive, the matter Lagrangian for string gases yields a potential for the size moduli which satisfies the de Sitter conjecture with the condition $\frac{|\nabla V|}{V}\ge \frac{1}{\sqrt{p}}\frac{1}{M_p}$, where $p$ is the number of compactified dimensions. Moreover, the moduli find themselves stabilized at the self-dual radius, and gravity naturally emerges as the weakest force.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2020)·20 citations
14. 14*

    Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes

    Jia Jie Li🇩🇪 · Armen Sedrakian🇩🇪 · Mark Alford🇺🇸

    We compute the mass, radius and tidal deformability of stars containing phase transitions from hadronic to quark phase(s). These quantities are computed for three types of hadronic envelopes: purely nuclear, hyperonic, and $\Delta$-resonance--hyperon admixed matter. We consider either a single first-order phase transition to a quark phase with a maximally stiff equation of state (EOS) or two sequential first-order phase transitions mimicking a transition from hadronic to a quark matter phase followed by a second phase transition to another quark phase. We explore the parameter space which produces low-mass twin and triplet configurations where equal-mass stars have substantially different radii and tidal deformabilities. We demonstrate that while for purely hadronic stiff EOS the obtained maximum mass is inconsistent with the upper limit on this quantity placed by GW170817, the inclusion of the hyperonic and $\Delta$-resonance degrees of freedom, as well as the deconfinement phase transition at sufficiently low density, produces a configuration of stars consistent with this limit. The obtained hybrid star configurations are in the mass range relevant for the interpretation of the GW170817 event. We compare our results for the tidal deformability with the limits inferred from GW170817 showing that the onset of non-nucleonic phases, such as $\Delta$-resonance--hyperon admixed phase and/or the quark phase(s), are favored by this data if the nuclear EOS is stiff. Also, we show that low-mass twins and especially triplets proliferate the number of combinations of possible types of stars that can undergo a merger event, the maximal number being six in the case of triplets. The prospects for uncovering the first-order phase transition(s) to and in quark matter via measurements of tidal deformabilities in merger events are discussed.

    ↳ astro-ph.HEhep-phnucl-thPRD(2020)·73 citations
15. 15*

    Meson spectrum of Sp(4) lattice gauge theory with two fundamental Dirac fermions

    Ed Bennett🇬🇧 · Deog Ki Hong🇰🇷 · Jong-Wan Lee🇰🇷 · C.-J. David Lin🇹🇼 · Biagio Lucini🇬🇧 · Maurizio Piai🇬🇧 · Davide Vadacchino🇮🇹

    We calculate the meson spectrum of the Sp(4) lattice gauge theory coupled to two fundamental flavours of dynamical Dirac fermions. We focus on some of the lightest (flavoured) spin-0 and spin-1 states. This theory provides an ultraviolet completion for composite Higgs models based upon the SU(4)/Sp(4) coset. We analyse the strongly coupled dynamics in isolation, without explicit coupling to the standard model. We carry out continuum extrapolations using dynamical ensembles generated at five different values of bare lattice coupling, and for several values of the bare fermion mass. We fit the resulting meson masses and decay constants to a low-energy effective field theory built along the ideas of hidden local symmetry. We also compare our results to those of other closely related lattice gauge theories, which have matter content consisting of two fundamental Dirac flavours.

    ↳ hep-lathep-phPoS(2019)·7 citations
16. 16*

    Charmed hadron chemistry in relativistic heavy-ion collisions

    Shanshan Cao🇺🇸 · Kai-Jia Sun🇺🇸 · Shu-Qing Li🇨🇳 · Shuai Y.F. Liu🇺🇸 · Wen-Jing Xing🇨🇳 · Guang-You Qin🇨🇳 · Che-Ming Ko🇺🇸

    We develop for charmed hadron production in relativistic heavy-ion collisions a comprehensive coalescence model that includes an extensive set of $s$ and $p$-wave hadronic states as well as the strict energy-momentum conservation, which ensures the boost invariance of the coalescence probability and the thermal limit of the produced hadron spectrum. By combining our hadronization scheme with an advanced Langevin-hydrodynamics model that incorporates both elastic and inelastic energy loss of heavy quarks inside the dynamical quark-gluon plasma, we obtain a successful description of the $p_{\mathrm{T}}$-integrated and differential ${\Lambda }_c/D^0$ and $D_s/D^0$ ratios measured at RHIC and the LHC. We find that including the effect of radial flow of the medium is essential for describing the enhanced ${\Lambda }_c/D^0$ ratio observed in relativistic heavy-ion collisions. We also find that the puzzling larger ${\Lambda }_c/D^0$ ratio observed in Au+Au collisions at RHIC than in Pb+Pb collisions at the LHC is due to the interplay between the effects of the QGP radial flow and the charm quark transverse momentum spectrum at hadronization. Our study further suggests that charmed hadrons have larger sizes in medium than in vacuum.

    ↳ nucl-thhep-phnucl-exPLB(2020)·73 citations
17. 17*

    Expression of Interest for the CODEX-b Detector

    Giulio Aielli🇮🇹 · Eli Ben-Haim🇫🇷 · Roberto Cardarelli🇮🇹 · Matthew John Charles🇫🇷 · Xabier Cid Vidal🇪🇸 · Victor Coco🇨🇭 · Biplab Dey🇨🇳 · Raphael Dumps🇨🇭 · Jared A. Evans🇺🇸 · George Gibbons🇬🇧 · Olivier Le Dortz🇫🇷 · Vladimir V. Gligorov🇫🇷 and 16 other authors

    This document presents the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEX-$\beta$, to be operated during Run 3 of the LHC. Our development of the CODEX-b physics case synthesizes `top-down' and `bottom-up' theoretical approaches, providing a detailed survey of both minimal and complete models featuring LLPs. Several of these models have not been studied previously, and for some others we amend studies from previous literature: In particular, for gluon and fermion-coupled axion-like particles. We moreover present updated simulations of expected backgrounds in CODEX-b's actively shielded environment, including the effects of shielding propagation uncertainties, high-energy tails and variation in the shielding design. Initial results are also included from a background measurement and calibration campaign. A design overview is presented for the CODEX-$\beta$ demonstrator detector, which will enable background calibration and detector design studies. Finally, we lay out brief studies of various design drivers of the CODEX-b experiment and potential extensions of the baseline design, including the physics case for a calorimeter element, precision timing, event tagging within LHCb, and precision low-momentum tracking.

    ↳ hep-exhep-phEPJC(2020)·193 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.