Fri·Sep 20, 2019Friday·September 20, 2019

1. 01*

   Lepton flavor violating ${\Lambda }_b\to \Lambda {\ell }_1{\ell }_2$ decay

   Diganta Das🇮🇳

   Inspired by the recent hints of lepton flavor universality violation in $b\to s\ell \ell$ and $b\to c\ell \nu$ transitions, we study lepton flavor violating exclusive ${\Lambda }_b\to \Lambda {\ell }_1^{+}{\ell }_2^{-}$ (${\ell }_1\ne {\ell }_2$) decay, which is forbidden in the Standard Model. Starting from a general effective Hamiltonian for a $b\to s{\ell }_1^{+}{\ell }_2^{-}$ transition that includes vector and axial-vector operators, and scalar and pseudo-scalar operators, we derive a two-fold decay distribution of ${\Lambda }_b\to \Lambda {\ell }_1^{+}{\ell }_2^{-}$. The distribution helps us to construct the differential branching ratio and the lepton side forward-backward asymmetry, which are studied in a vector leptoquark model. The parameter space of the vector leptoquark model is constrained by low energy observables.

   hep-phEPJC(2019)·17 citations
2. 02*

   LHC phenomenology with hidden sector dark matter: a long-lived stau and heavy Higgs in an observable range

   Amin Aboubrahim🇺🇸 · Pran Nath🇺🇸

   The presence of a hidden sector with very weak interactions with the standard model has significant implications on LHC signatures. In this work we discuss LHC phenomenology with the inclusion of a hidden sector by a $U(1)$ extension of MSSM/SUGRA. We consider both kinetic mixing and Stueckelberg mass mixing between the $U(1)$ gauge field of the hidden sector and $U(1{)}_Y$ of the visible sector. Such a model has an extended parameter space. We consider here two limited regions of this parameter space. In the first case we consider a $U(1)$ gauge field along with chiral fields needed for the Stueckelberg mechanism to operate and discuss the mixing between the hidden and the visible sectors. Here if the stau is the lightest sparticle in the MSSM sector and the neutralino of the hidden sector is the LSP of the full system and a dark matter candidate, the stau can be long-lived and decay inside an LHC detector tracker. In the second case we include extra vectorlike matter in the hidden sector which can give rise to a Dirac fermion in addition to the two neutralinos in the hidden sector. The neutralino sector now has six neutralinos and we assume that the lightest of these is the LSP and is higgsino-like. In this case the dark matter is constituted of a Majorana and a Dirac fermion, and a small $\mu$ leads to heavy Higgs boson masses which reside in the observable range of HL-LHC and HE-LHC.

   hep-phhep-ex5 citations
3. 03*

   Direct CP violation in internal W-emission dominated baryonic B decays

   Y.K. Hsiao🇨🇳 · Shang-Yuu Tsai🇨🇳 · Eduardo Rodrigues🇺🇸

   The observation of CP violation has been experimentally verified in numerous $B$ decays but is yet to be confirmed in final states with half-spin particles. We focus our attention on baryonic $B$-meson decays mediated dominantly through internal $W$-emission processes and show that they are promising processes to observe for the first time the CP violating effects in $B$ decays to final states with half-spin particles. Specifically, we study the ${\bar{B}}^0\to p\bar{p}{\pi }^0({\rho }^0)$ and ${\bar{B}}^0\to p\bar{p}{\pi }^{+}{\pi }^{-}$ decays. We obtain $\mathcal{B}({\bar{B}}^0\to p\bar{p}{\pi }^0)=(5.0\pm 2.1)\times 10^{-7}$, in agreement with current data, and $\mathcal{B}({\bar{B}}^0\to p\bar{p}{\rho }^0)\simeq \mathcal{B}({\bar{B}}^0\to p\bar{p}{\pi }^0)/3$. Furthermore, we find ${\mathcal{A}}_{CP}({\bar{B}}^0\to p\bar{p}{\pi }^0,p\bar{p}{\rho }^0,p\bar{p}{\pi }^{+}{\pi }^{-})=(-16.8\pm 5.4,-12.6\pm 3.0,-11.4\pm 1.9)\%$. With measured branching fractions $\mathcal{B}({\bar{B}}^0\to p\bar{p}{\pi }^0,p\bar{p}{\pi }^{+}{\pi }^{-})\sim \mathcal{O}(10^{-6})$, we point out that ${\mathcal{A}}_{CP}\sim -(10-20)\%$ can be new observables for CP violation, accessible to the Belle~II and/or LHCb experiments.

   hep-phhep-exEPJC(2020)·14 citations
4. 04*

   Low scale seesaw models for low scale $U(1{)}_{L_{\mu }-L_{\tau }}$ symmetry

   Takeshi Araki🇯🇵 · Kento Asai🇯🇵 · Joe Sato🇯🇵 · Takashi Shimomura🇯🇵

   We propose models for neutrino masses and mixing in the framework of low scale $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge extension of the standard model. The models are designed to spontaneously break $U(1{)}_{L_{\mu }-L_{\tau }}$ so that the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge boson acquires an MeV scale mass, which is required to solve the long-standing problem of muon anomalous magnetic moment. Tiny neutrino masses are obtained by simultaneously invoking the linear and the inverse seesaw mechanism, and we succeed in realizing two types of one-zero textures in the active neutrino mass matrix. Both of the obtained textures favor inverted neutrino mass ordering and are testable in next generation experiments of neutrinoless double beta decay. We also show that some of extra scalar bosons can have MeV scale masses and would have significant impacts on observations of high energy cosmic neutrinos.

   hep-phPRD(2019)·21 citations
5. 05*

   Distinctive features of hadronizing heavy quarks

   B. Z. Kopeliovich🇨🇱 · Jan Nemchik🇨🇿 · I. K. Potashnikova🇨🇱 · Ivan Schmidt🇨🇱

   The color field of a quark, stripped off in a hard reaction, is regenerated via gluon radiation. The space-time development of a jet is controlled by the coherence time of gluon radiation, which for heavy quarks is subject to the dead-cone effect, suppressing gluons with small transverse momenta. As a result, heavy quarks can radiate only a small fraction of the initial energy. This explains the peculiar shape of the measured heavy quark fragmentation function, which strongly peaks at large fractional momenta z. The fragmentation length distribution, related to the fragmentation function in a model independent way, turns out to be concentrated at distances much shorter than the confinement radius. This implies that the mechanisms of heavy quark fragmentation is pure perturbative.

   hep-phnucl-th3 citations
6. 06*

   Spacetime Colour Reconnection in Herwig 7

   Johannes Bellm🇸🇪 · Cody B Duncan🇦🇺 · Stefan Gieseke🇩🇪 · Miroslav Myska🇨🇿 · Andrzej Siódmok🇵🇱

   We present a model for generating spacetime coordinates in the Monte Carlo event generator Herwig 7, and perform colour reconnection by minimizing a boost-invariant distance measure of the system. We compare the model to a series of soft physics observables. We find reasonable agreement with the data, suggesting that $pp$-collider colour reconnection may be able to be applied in larger systems.

   hep-phEPJC(2019)·28 citations
7. 07*

   $J/\psi \to \gamma \pi \pi$, $\gamma {\pi }^0\eta$ reactions and the $f_0(980)$ and $a_0(980)$ resonances

   S. Sakai🇨🇳 · Wei-Hong Liang🇨🇳 · G. Toledo🇲🇽 · E. Oset🇪🇸

   We study the $J/\psi \to \gamma {\pi }^{+}{\pi }^{-}$, $\gamma {\pi }^0\eta$ reactions from the perspective that they come from the $J/\psi \to \varphi (\omega ){\pi }^{+}{\pi }^{-},{\rho }^0{\pi }^0\eta$ reactions, where the ${\rho }^0$, $\omega$, and $\varphi$ get converted into a photon via vector meson dominance. Using models successfully used previously to study the $J/\psi \to \omega (\varphi )\pi \pi$ reactions, we make determinations of the invariant mass distributions for ${\pi }^{+}{\pi }^{-}$ in the regions of the $f_0(500)$, $f_0(980)$, and for ${\pi }^0\eta$ in the region of the $a_0(980)$. The integrated differential widths lead to branching ratios below present upper bounds, but they are sufficiently large for future check in updated facilities.

   hep-phPRD(2020)·9 citations
8. 08*

   Inclusive and diffractive dijet photoproduction in UPCs at the LHC in NLO QCD

   V. Guzey🇷🇺 · M. Klasen🇩🇪

   We present a next-to-leading order QCD calculation of inclusive dijet photoproduction in ultraperipheral Pb-Pb collisions at the LHC and show that the results agree very well with various kinematic distributions measured by the ATLAS collaboration. The effect of including these data in nCTEQ or EPPS16 nuclear parton density functions (nPDFs) is then studied using the Bayesian reweighting technique. For an assumed total error of 5\% on the final data, its inclusion would lead to a significant reduction of the nPDF uncertainties of up to a factor of two at small values of the parton momentum fraction. As an outlook, we discuss future analyes of diffractive nPDFs, which are so far completely unknown.

   hep-phhep-exnucl-exnucl-thPoS(2020)·3 citations
9. 09*

   Sum rules for CP-violating operators of Weinberg type

   Ulrich Haisch🇩🇪 · Amando Hala🇩🇪

   We estimate the size of the hadronic matrix elements of CP-violating three-gluon and four-gluon Weinberg operators using sum-rule techniques. In the three-gluon case, we are able to reproduce the expressions given in earlier works, while the four-gluon results obtained in this article are new. Our paper therefore represents the first systematic study of contributions to the electric dipole moment of the neutron due to CP-violating dimension-six and dimension-eight operators. We provide many details on both the derivation of the sum rules as well as the analysis of the uncertainties that plague our final predictions.

   hep-phJHEP(2019)·52 citations
10. 10*

    Two loop QCD amplitudes for di-pseudo scalar production in gluon fusion

    Arunima Bhattacharya🇮🇳 · Maguni Mahakhud🇮🇳 · Prakash Mathews🇮🇳 · V. Ravindran🇮🇳

    We compute the radiative corrections to the four-point amplitude $g+g\to A+A$ in massless Quantum Chromodynamics (QCD) up to order $a_s^4$ in perturbation theory. We used the effective field theory that describes the coupling of pseudo-scalars to gluons and quarks directly, in the large top quark mass limit. Due to the CP odd nature of the pseudo-scalar Higgs boson, the computation involves careful treatment of chiral quantities in dimensional regularisation. The ultraviolet finite results are shown to be consistent with the universal infrared structure of QCD amplitudes. The infrared finite part of these amplitudes constitutes the important component of any next to next to leading order corrections to observables involving pair of pseudo-scalars at the Large Hadron Collider.

    hep-phJHEP(2020)·14 citations
11. 11*

    Strong decays of the explicitly exotic doubly charmed $DDK$ bound state

    Yin Huang🇨🇳 · Ming-Zhu Liu🇨🇳 · Ya-Wen Pan🇨🇳 · Li-Sheng Geng🇨🇳 · A. Martínez Torres🇧🇷 · K. P. Khemchandani🇧🇷

    Nowadays, it is generally accepted that the $DK$ interaction in isospin zero is strongly attractive and the $D_{s0}^{\ast }(2317)$ can be described as a $DK$ molecular state. Recent studies show that the three-body $DDK$ system binds as well with a binding energy about 60$\sim$70 MeV. The $DDK$ bound state has isospin $1/2$ and spin-parity $0^{-}$. If discovered either experimentally or in lattice QCD, it will not only provide further support on the molecular nature of the $D_{s0}^{\ast }(2317)$, but also provide a way to understand other exotic hadrons expected to be of molecular nature. In the present work, we study its two-body strong decay widths via triangle diagrams. We find that the partial decay width into $D{D}_s\pi$ is at the order of $2\sim 3$ MeV, which seems to be within the reach of the current experiments such as BelleII. As a result, we strongly recommend this decay channel of the $DDK$ bound state to be searched for experimentally.

    hep-phhep-exhep-latPRD(2020)·31 citations
12. 12*

    Exploring the low $\tan \beta$ region of two Higgs doublet models at the LHC

    Wei Su🇦🇺 · Martin White🇦🇺 · Anthony G. Williams🇦🇺 · Yongcheng Wu🇨🇦

    Current interpretations of the LHC results on two Higgs doublet models (2HDM) underestimate the sensitivity due to neglecting higher order effects. In this work, we revisit the impact of these effects using the current cross-section times branching ratio limits of the $A\to hZ,H\to VV$ and $H\to hh$ channels. With a degenerate heavy Higgs mass $m_{\Phi }$, we find that the LHC searches gain sensitivity to the small $\tan \beta$ region after including loop corrections, even close to $\cos (\beta -\alpha )=0$ which is not reachable at tree level for all types of 2HDM. For a benchmark point with $m_{\Phi }=300$ GeV, $\tan \beta <1.8(1.2)$ can be probed for the Type-I(II) 2HDM model for $\cos (\beta -\alpha )=0$. When the deviation from $\cos (\beta -\alpha )=0$ is larger, the region for which current searches have exclusion potential becomes larger.

    hep-phEPJC(2021)·12 citations
13. 13*

    Reevaluating Uncertainties in $\bar{B}\to X_s\gamma$

    Ayesh Gunawardana🇺🇸

    The rare inclusive decay $\bar{B}\to X_s\gamma$ is an important probe of physics beyond the standard model. The largest uncertainty on the decay rate and CP asymmetry comes from operators that appear at order $1/m_b$ in the heavy quark expansion. One of the three leading contributions in the heavy quark expansion, $Q_1^q-Q_{7\gamma }$ is described by a non-local function whose moments are related to HQET parameters. We use recent progress in our knowledge of these parameters to better constrain their contributions to the total rate and CP asymmetry.

    hep-phhep-ex1 citation
14. 14*

    Precision phenomenology with MCFM

    John Campbell🇺🇸 · Tobias Neumann🇺🇸

    Without proper control of numerical and methodological errors in theoretical predictions at the per mille level it is not possible to study the effect of input parameters in current hadron-collider measurements at the required precision. We present a new version of the parton-level code MCFM that achieves this requirement through its highly-parallelized nature, significant performance improvements and new features. An automatic differential cutoff extrapolation is introduced to assess the cutoff dependence of all results, thus ensuring their reliability and potentially improving fixed-cutoff results by an order of magnitude. The efficient differential study of PDF uncertainties and PDF set differences at NNLO, for multiple PDF sets simultaneously, is achieved by exploiting correlations. We use these improvements to study uncertainties and PDF sensitivity at NNLO, using 371 PDF set members. The work described here permits NNLO studies that were previously prohibitively expensive, and lays the groundwork necessary for a future implementation of NNLO calculations with a jet at Born level in MCFM.

    hep-phhep-exJHEP(2019)·213 citations
15. 15*

    Towards A UV-Model of Kinetic Mixing and Portal Matter

    Thomas D. Rueter🇺🇸 · Thomas G. Rizzo🇺🇸

    The nature of dark matter (DM) and how it might interact with the particles of the Standard Model (SM) is an ever-growing mystery. It is possible that the existence of new `dark sector' forces, yet undiscovered, are the key to solving this fundamental problem, and one might hope that in the future such forces might even be `unified' with the ones we already know in some UV-complete framework. In this paper, following a bottom-up approach, we attempt to take the first steps in the construction of such a framework. The much-discussed possibility of the kinetic mixing (KM) of the `dark photon' with the hypercharge gauge boson of the SM via loops of portal matter (PM) fields, charged in both sectors, offers an attractive starting point for these efforts. Given the anticipated finite strength of the KM in a UV-complete theory, the absence of anomalies, and the lifetime constraints on the PM fields arising from CMB and nucleosynthesis constraints, PM must behave as vector-like copies of the known SM fermion fields, such as those which appear naturally in $E_6$-type models. Within such a setup, the SM and their corresponding partner PM fields would be related by a new $SU(2{)}_I$ gauge symmetry. With this observation as a springboard, we construct a generalization of these ideas where $SU(2{)}_I$ is augmented by an additional $U(1{)}_{I_Y}$ factor so that the light dark photon is the result of a symmetry breaking analogous to the SM, \ie, $SU(2{)}_I\times U(1{)}_{I_Y}\to U(1{)}_D$, but with $U(1{)}_D$ now also broken at the $\lesssim$ GeV scale. While SM fields are $U(1{)}_D$ singlets, as in the conventional dark photon approach, they transform nontrivially under the full $SU(2{)}_I\times U(1{)}_{I_Y}$ gauge group. This approach leads to numerous interesting signatures, both at low energies and at colliders, and can be viewed as an initial step in the construction of a more UV-complete framework.

    hep-phPRD(2020)·31 citations
16. 16*

    2-, 3- and 4-Body Decays in the Constructive Standard Model

    Neil Christensen🇺🇸 · Bryan Field🇺🇸 · Annie Moore🇺🇸 · Santiago Pinto🇺🇸

    We further develop the massive constructive theory of the Standard Model and use it to calculate the amplitude and squared amplitude for all two-body decays, a collection of weak three-body decays, as well as Higgs decay to four neutrinos. We compare our results with those from Feynman diagrams and find complete agreement. We show that in all the cases considered here, the amplitudes of massive constructive theories are significantly simpler than those resulting from Feynman diagrams. In fact, a naive counting of the number of calculations required for a matrix-element generator to compute a phase-space point is orders-of-magnitude smaller for the result coming from the constructive method suggesting that these generators might benefit from this method in the future, even in the case of massive weak amplitudes. We also anticipate that our simpler expressions will produce numerically more stable expressions.

    hep-phhep-thPRD(2020)·27 citations
17. 17*

    Triple Higgs boson production to six $b$-jets at a 100 TeV proton collider

    Andreas Papaefstathiou🇳🇱 · Gilberto Tetlalmatzi-Xolocotzi🇳🇱 · Marco Zaro🇳🇱

    We investigate the production of three Higgs bosons at a proton-proton collider running at a centre-of-mass energy of 100 TeV, all of which decay into $b$-jets. This final state encapsulates by far the largest fraction of the total cross section of triple Higgs boson production, approximately $20\%$. We examine, by constructing detailed phenomenological analyses, two scenarios: (i) one in which the triple and quartic Higgs boson self-couplings are modified independently by new phenomena with respect to their Standard Model (SM) values and (ii) an extension of the SM by a gauge-singlet scalar that could drive first-order electroweak phase transition, within the context of the so-called xSM. In the former, we find that competitive constraints of $\mathcal{O}(1)$ can be placed on the quartic coupling and in the latter we demonstrate that it will be possible to obtain important information on the structure of the extended scalar sector.

    hep-phEPJC(2019)·50 citations
18. 18*

    Directional Dark Matter Detection in Anisotropic Dirac Materials

    Ahmet Coskuner🇺🇸 · Andrea Mitridate🇮🇹 · Andres Olivares🇬🇧 · Kathryn M. Zurek🇺🇸

    Dirac materials, because of their small $\mathcal{O}(\text{mbox}meV)$ band gap, are a promising target for dark photon-mediated scattering and absorption of light dark matter. In this paper, we characterize the daily modulation rate of dark matter interacting with a Dirac material due to anisotropies in their crystal structure. We show that daily modulation is an $\mathcal{O}(1)$ fraction of the total rate for dark matter scattering in the Dirac material ZrTe${}_5$. When present, the modulation is dominated by the orientation of the material's dielectric tensor with respect to the dark matter wind, and is maximized when the crystal is oriented such that the dark matter wind is completely aligned with the largest and smallest components of the dielectric tensor at two different times of the day. Because of the large modulation, any putative dark matter scattering signal could be rapidly verified or ruled out by changing the orientation of the crystal with respect to the wind and observing how the daily modulation pattern changes.

    hep-phPRD(2021)·111 citations
19. 19*

    Axion Quark Nuggets and how a Global Network can discover them

    Dmitry Budker🇩🇪 · Victor V. Flambaum🇦🇺 · Xunyu Liang🇨🇦 · Ariel Zhitnitsky🇨🇦

    We advocate an idea that the presence of the daily and annual modulations of the axion flux on the Earth surface may dramatically change the strategy of the axion searches. Our computations are based on the so-called Axion Quark Nugget (AQN) dark matter model which was originally put forward to explain the similarity of the dark and visible cosmological matter densities ${\Omega }_{\mathrm{dark}}\sim {\Omega }_{\mathrm{visible}}$. In our framework, the population of galactic axions with mass $10^{-6}\mathrm{eV}\lesssim m_a\lesssim 10^{-3}\mathrm{eV}$ and velocity $<v_a>\sim 10^{-3}c$ will be always accompanied by the axions with typical velocities $<v_a>\sim 0.6c$ emitted by AQNs. We formulate the broadband detection strategy to search for such relativistic axions by studying the daily and annual modulations. We describe several tests which could effectively discriminate a true signal from noise. These AQN-originated axions can be observed as correlated events which could be recorded by synchronized stations in the global network. The correlations can be effectively studied if the detectors are positioned at distances shorter than a few hundred kilometres.

    hep-phastro-ph.COphysics.atom-phPRD(2020)·37 citations
20. 20*

    Two Pion Photo- and Electroproduction with CLAS

    Victor I Mokeev🇺🇸

    Exclusive ${\pi }^{+}{\pi }^{-}p$ photo- and electroproduction data from CLAS have considerably extended the information on the spectrum and structure of nucleon resonances. The data from the ${\pi }^{+}{\pi }^{-}p$ and $N\pi$ channels have provided results on the electrocouplings of most resonances in the mass region up to 1.8 GeV and at photon virtualities up to 5.0 GeV${}^2$. The recent CLAS data on ${\pi }^{+}{\pi }^{-}p$ photoproduction have improved knowledge on the photocouplings of nucleon resonances in the mass range of 1.6 GeV $<$ $M_{N^{\ast }}$ $<$ 2.0 GeV and on their decays to the $\pi \Delta$ and $\rho p$ final hadron states. For the first time, the electrocouplings of the $N(1440)1/2^{+}$ and $N(1520)3/2^{-}$ excited states have become available from ${\pi }^{+}{\pi }^{-}p$ data at 2.0 GeV${}^2$ $<$ $Q^2$ $<$ 5.0 GeV${}^2$. Analyses of the combined ${\pi }^{+}{\pi }^{-}p$ photo- and electroproduction data have revealed evidence for the candidate-state $N^{\prime }(1720)3/2^{+}$. The new results on the nucleon resonance spectrum, electroexcitation amplitudes from analysis of the CLAS ${\pi }^{+}{\pi }^{-}p$ photo- and electroproduction data, and their impact on the exploration of strong QCD are presented.

    ↳ nucl-exhep-ph4 citations
21. 21*

    Anomaly Inflow and the $\eta$-Invariant

    Edward Witten🇺🇸 · Kazuya Yonekura🇯🇵

    Perturbative fermion anomalies in spacetime dimension $d$ have a well-known relation to Chern-Simons functions in dimension $D=d+1$. This relationship is manifested in a beautiful way in "anomaly inflow" from the bulk of a system to its boundary. Along with perturbative anomalies, fermions also have global or nonperturbative anomalies, which can be incorporated by using the $\eta$-invariant of Atiyah, Patodi, and Singer instead of the Chern-Simons function. Here we give a nonperturbative description of anomaly inflow, involving the $\eta$-invariant. This formula has been expected in the past based on the Dai-Freed theorem, but has not been fully justified. It leads to a general description of perturbative and nonperturbative fermion anomalies in $d$ dimensions in terms of an $\eta$-invariant in $D$ dimensions. This $\eta$-invariant is a cobordism invariant whenever perturbative anomalies cancel.

    ↳ hep-thcond-mat.str-elhep-lathep-ph+2139 citations
22. 22*

    Dark Matter Mass and Anisotropy in Directional Detector

    Keiko I. Nagao🇯🇵

    Velocity distribution of dark matter is supposed to be isotropic Maxwell-Boltzmann distribution in most cases, however, other distribution models including anisotropic one are suggested by simulations. Directional direct detection of dark matter is expected to be a hopeful way to discriminate isotropic distribution from anisotropic one. We investigate the possibility to obtain the anisotropy and WIMP mass by Monte-Carlo simulation supposing the directional detector.

    ↳ astro-ph.COhep-exhep-ph0 citations
23. 23*

    On thermal Nieh-Yan anomaly in Weyl superfluids

    J. Nissinen🇫🇮 · G.E. Volovik🇫🇮

    We discuss the possibility of the torsional Nieh-Yan anomaly of the type $\mu (e{j}_5^{\mu })=\gamma T^2({\mathcal{T}}^a\wedge {\mathcal{T}}_a)$ in Weyl superfluids, where $T$ is temperature and ${\mathcal{T}}^a$ is the effective or emergent torsion from the superfluid order parameter. As distinct from the dimensionful ultraviolet (UV) parameter ${\Lambda }^2$ in the conventional torsional Nieh-Yan anomaly, the parameter $\gamma$ is dimensionless in canonical units. This suggests that such dimensionless parameter may be fundamental, being determined by the geometry, topology and number of chiral quantum fields in the system. By comparing this to a Weyl superfluid with low-temperature corrections, $T\ll {\Delta }_0$, we show that such a term does exist in the hydrodynamics of a chiral $p$-wave superfluid, such as ${}^3$He-A, or a chiral superconductor. We also discuss and show how other $T^2$ terms of similar form and of the same order in gradients, coming from e.g. Fermi-liquid corrections and the chiral chemical potential, can also be expressed in terms of dimensionless fundamental parameters with emergent low-energy relativistic fields. Lastly, we discuss our results in comparison to relativistic Weyl fermions and the connection of the torsional gravitational anomalies to thermal transport in Weyl systems.

    ↳ cond-mat.str-elgr-qchep-phPRResearch(2020)·45 citations
24. 24*

    On the baryon-color-flavor (BCF) anomaly in vector-like theories

    Mohamed M. Anber🇺🇸 · Erich Poppitz🇨🇦

    We consider the most general fractional background fluxes in the color, flavor, and baryon number directions, compatible with the faithful action of the global symmetry of a given theory. We call the obstruction to gauging symmetries revealed by such backgrounds the baryon-color-flavor (BCF) 't Hooft anomaly. We apply the BCF anomaly to vector-like theories, with fermions in higher-dimensional representations of arbitrary N-ality, and derive non-trivial constraints on their IR dynamics. In particular, this class of theories enjoys an independent discrete chiral symmetry and one may ask about the fate of this symmetry in the background of BCF fluxes. We show that, under certain conditions, an anomaly between the chiral symmetry and the BCF background rules out massless composite fermions as the sole player in the IR: either the composites do not form or additional contributions to the matching of the BCF anomaly are required. We can also give a flavor-symmetric mass to the fermions, smaller than or of order the strong scale of the theory, and examine the $\theta$-angle periodicity of the theory in the BCF background. Interestingly, we find that the conditions that rule out the composites are the exact same conditions that lead to an anomaly of the $\theta$ periodicity: the massive theory will experience a phase transition as we vary $\theta$ from $0$ to $2\pi$.

    ↳ hep-thhep-lathep-phJHEP(2019)·51 citations
25. 25*

    Cosmic Ray Small-Scale Anisotropies in Quasi-Linear Theory

    Philipp Mertsch (Aachen)🇩🇪 · Markus Ahlers (Copenhagen)🇩🇰

    The distribution of arrival directions of cosmic rays is remarkably isotropic, which is a consequence of their repeated scattering in magnetic fields. Yet, high-statistics observatories like IceCube and HAWC have revealed the presence of small-scale structures at levels of 1 part in 10,000 at hundreds of TeV, which are not expected in typical diffusion models of cosmic rays. We follow up on the suggestion that these small-scale anisotropies are a result of cosmic ray streaming in a particular realisation of the turbulent magnetic field within a few scattering lengths in our local Galactic neighbourhood. So far, this hypothesis has been investigated mostly numerically, by tracking test particles through turbulent magnetic fields. For the first time, we present an analytical computation that through a perturbative approach allows predicting the angular power spectrum of cosmic ray arrival directions for a given model of turbulence. We illustrate this method for a simple, isotropic turbulence model and we find remarkable agreement with the results of numerical studies.

    ↳ astro-ph.HEhep-phJCAP(2019)·10 citations
26. 26*

    Observation of Complex Time Structures in the Cosmic Ray Fluxes by the Alpha Magnetic Spectrometer on the ISS

    Davide Rozza (for the AMS-02 Collaboration)🇮🇹

    We present high-statistics, precision measurements by AMS of the detailed time and rigidity dependence of the primary cosmic-ray electron, positron, proton and helium fluxes over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. We report the observation of short-term structures on the timescale of months coincident in all the fluxes. These structures are not visible in the positron-to-electron flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over ~800 days from one value to another.

    ↳ astro-ph.HEhep-phphysics.space-ph0 citations
27. 27*

    Anatomy of Deconfinement

    Masanori Hanada🇬🇧 · Antal Jevicki🇺🇸 · Cheng Peng🇺🇸 · Nico Wintergerst🇩🇰

    In the weak coupling limit of $\mathrm{SU}(N)$ Yang-Mills theory and the $\mathrm{O}(N)$ vector model, explicit state counting allows us to demonstrate the existence of a partially deconfined phase: $M$ of $N$ colors deconfine, and $\frac{M}{N}$ gradually grows from zero (confinement) to one (complete deconfinement). We point out that the mechanism admits a simple interpretation in the form of spontaneous breaking of gauge symmetry. In terms of the dual gravity theory, such breaking occurs during the formation of a black hole. We speculate whether the breaking and restoration of gauge symmetry can serve as an alternative definition of the deconfinement transition in theories without center symmetry, such as QCD. We also discuss the role of the color degrees of freedom in the emergence of the bulk geometry in holographic duality.

    ↳ hep-thhep-lathep-phJHEP(2019)·55 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.