Wed·Feb 20, 2019Wednesday·February 20, 2019

1. 01*

   Neutrino Tridents at DUNE

   Wolfgang Altmannshofer🇺🇸 · Stefania Gori🇺🇸 · Justo Martin-Albo🇺🇸 · Alexandre Sousa🇺🇸 · Michael Wallbank🇺🇸

   The DUNE near detector will collect an unprecedented large number of neutrino interactions, allowing the precise measurement of rare processes such as neutrino trident production, i.e. the generation of a lepton-antilepton pair through the scattering of a neutrino off a heavy nucleus. The event rate of this process is a powerful probe to a well-motivated parameter space of new physics beyond the Standard Model. In this paper, we perform a detailed sensitivity study of the DUNE near detector to neutrino tridents. We provide state-of-the-art predictions for the Standard Model cross sections and corresponding event rates at the near detector for the nu_mu -> nu_mu mu^+ mu^-, nu_mu -> nu_mu e^+e^- and nu_mu -> nu_e e^+ mu^- trident interactions (and the corresponding anti-neutrino modes), discussing their uncertainties. We analyze all relevant backgrounds, utilize a Geant4-based simulation of the DUNE-near detector liquid argon TPC (the official DUNE simulation at the time of writing this paper), and identify a set of selection cuts that would allow the DUNE near detector to measure the nu_mu -> nu_mu mu^+ mu^- cross section with a ~25% accuracy after running in neutrino and anti-neutrino modes for ~3 years each. This would lead to the most precise measurement of the trident process, surpassing the previous measurement by the CCFR collaboration. We show that this measurement would be highly sensitive to new physics, and, in particular, we find that the parameter space of models with gauged L_mu - L_tau that can explain the (g-2)_mu anomaly could be covered almost entirely. As a byproduct, a new Monte Carlo tool to generate neutrino trident events is made publicly available.

   hep-phhep-exPRD(2019)·140 citations
2. 02*

   Single heavy baryons with chiral partner structure in a three-flavor chiral model

   Yohei Kawakami🇯🇵 · Masayasu Harada🇯🇵

   We construct an effective hadronic model including single heavy baryons (SHBs) belonging to the $(3,3)$ representation under $\text{mbox}SU(3{)}_L\times \text{mbox}SU(3{)}_R$ symmetry, respecting the chiral symmetry and heavy-qaurk spin-flavor symmetry. When the chiral symmetry is spontaneously broken, the SHBs are divided into the baryons with negative parity of $\bar{3}$ representation under $\text{mbox}SU(3)$ flavor symmetry which is the chiral partners to the ones with positive parity of $6$ representation. We determine the model parameters from the available experimental data for the masses and strong decay widths of ${\Sigma }_c^{(\ast )}$, ${\Lambda }_c(2595)$, ${\Xi }_c(2790)$, and ${\Xi }_c(2815)$. Then, we predict the masses and strong decay widths of other baryons including ${\Xi }_b$ with negative parity. We also study radiative decays of SHBs including ${\Omega }_c^{\ast }$ and ${\Omega }_b^{\ast }$ with positive parity.

   hep-phPRD(2019)·45 citations
3. 03*

   Relaxation of the Cosmological Constant

   Peter W. Graham🇺🇸 · David E. Kaplan🇺🇸 · Surjeet Rajendran🇺🇸

   We present a model that naturally tunes a large positive cosmological constant to a small cosmological constant. A slowly rolling scalar field decreases the cosmological constant to a small negative value, causing the universe to contract, thus reheating it. An expanding universe with a small positive cosmological constant can be obtained, respectively, by coupling this solution to any model of a cosmological bounce and coupling the scalar field to a sector that undergoes a technically natural phase transition at the meV scale. A robust prediction of this model is a rolling scalar field today with some coupling to the standard model. This can potentially be experimentally probed in a variety of cosmological and terrestrial experiments, such as probes of the equation of state of dark energy, birefringence in the cosmic microwave background and terrestrial tests of Lorentz violation.

   hep-phgr-qchep-thPRD(2019)·57 citations
4. 04*

   Light scalars in composite Higgs models

   G.Cacciapaglia🇫🇷 · G.Ferretti🇸🇪 · T.Flacke🇰🇷 · H.Serôdio🇸🇪

   A composite Higgs boson is likely to be accompanied by additional light states generated by the same dynamics. This expectation is substantiated when realising the composite Higgs mechanism by an underlying gauge theory. We review the dynamics of such objects, which may well be the first sign of compositeness at colliders. We also update our previous analysis of the bounds from LHC searches to the latest results, and discuss the projected reach of the High-Luminosity run.

   hep-phFront.in Phys.(2019)·106 citations
5. 05*

   The role of the stochastic color field fluctuations on $J/\psi$ suppression in ultra-relativistic heavy-ion collisions

   Ashik Ikbal Sheikh🇮🇳 · Zubayer Ahammed🇮🇳 · M.G. Mustafa🇮🇳

   We consider the effect of the stochastic color field fluctuations in addition to the collisional as well as the radiative energy losses in the propagation of charm quarks in the hot and dense deconfined medium of quarks and gluons created in ultra-relativistic heavy-ion collisions. These fluctuations lead to energy gain of the propagating charm quarks. We construct and solve Langevin transport equations for charm quarks under the evolving background matter described by the ($3+1$)-D relativistic viscous hydrodynamics. Considering the energy gain of charm quarks, the nuclear modification factor $R_{AA}$ of $J/\psi$ is calculated. Interestingly, the experimental measurements for $J/\psi$ suppression in $Au-Au$ collisions at $\sqrt{s_{NN}}=200$ GeV by PHENIX Collaboration and $Pb-Pb$ collisions at $\sqrt{s_{NN}}=2.76$ TeV by ALICE and CMS Collaborations, can be nicely described with the effect of these field fluctuations without invoking the regeneration phenomena.

   hep-phnucl-th0 citations
6. 06*

   Sivers and Boer-Mulders GTMDs in Light-front Holographic Quark-diquark Model

   Dipankar Chakrabarti🇮🇳 · Narindar Kumar🇮🇳 · Tanmay Maji🇨🇳 · Asmita Mukherjee🇮🇳

   We calculate the time reversal odd (T-odd) generalized transverse momentum dependent parton distributions (GTMDs) $F_{1,2}^o$ and $H_{1,1}^o$ in a light-front quark-diquark model based on ADS/QCD. In the limit of zero momentum transfer, these reduce to the Sivers and Boer-Mulders TMDs respectively. We have incorporated both scalar and axial vector diquarks in the model and obtained an overlap representation of the GTMDs using the light-front wave functions (LFWFs). Contribution from the final state interaction is incorporated at the level of one gluon exchange as a phase factor in the LFWF. We show that the final state interaction term can be factored out in this model and this part is the same for both GTMDs. We also present the corresponding Wigner distributions.

   hep-phEur.Phys.J.Plus(2020)·27 citations
7. 07*

   Spectrum of the $uudc\bar{c}$ hidden charm pentaquark with an SU(4) flavor-spin hyperfine interaction

   Fl. Stancu🇧🇪

   We study a few of the lowest states of the pentaquark $uudc\overline{c}$, of positive and negative parity, in a constituent quark model with an SU(4) flavor-spin hyperfine interaction. For positive parity we introduce space wave functions of appropriate permutation symmetry with one unit of orbital angular momentum in the internal motion of the four-quark subsystem or an orbital excitation between the antiquark and the four quark subsystem which remains in the ground state. We show that the lowest positive parity states $1/2^{+},3/2^{+}$ are provided by the first alternative and are located below the $1/2^{-}$ and the $1/2^{+}$ states with all quarks in the ground state. We compare our results with the LHCb three narrow pentaquark structures reported in 2019.

   hep-phEPJC(2019)·31 citations
8. 08*

   Automating the Construction of Jet Observables with Machine Learning

   Kaustuv Datta🇨🇭 · Andrew Larkoski🇺🇸 · Benjamin Nachman🇺🇸

   Machine-learning assisted jet substructure tagging techniques have the potential to significantly improve searches for new particles and Standard Model measurements in hadronic final states. Techniques with simple analytic forms are particularly useful for establishing robustness and gaining physical insight. We introduce a procedure to automate the construction of a large class of observables that are chosen to completely specify $M$-body phase space. The procedure is validated on the task of distinguishing $H\to b\bar{b}$ from $g\to b\bar{b}$, where $M=3$ and previous brute-force approaches to construct an optimal product observable for the $M$-body phase space have established the baseline performance. We then use the new method to design tailored observables for the boosted $Z^{\prime }$ search, where $M=4$ and brute-force methods are intractable. The new classifiers outperform standard $2$-prong tagging observables, illustrating the power of the new optimization method for improving searches and measurement at the LHC and beyond.

   hep-phhep-exPRD(2019)·49 citations
9. 09*

   Simple and Precise Factorization of the Jarlskog Invariant for Neutrino Oscillations in Matter

   Peter B. Denton🇺🇸 · Stephen J. Parke🇺🇸

   For neutrino propagation in matter, we show that the Jarlskog invariant, which controls the size of true CP violation in neutrino oscillation appearance experiments, factorizes into three pieces: the vacuum Jarlskog invariant times two simple two-flavor matter resonance factors that control the matter effects for the solar and atmospheric resonances independently. If the solar effective matter potential and the atmospheric effective $\Delta m^2$ are chosen carefully for these two resonance factors, then the fractional corrections to this factorization are an impressive 0.04\% or smaller. We also show that the inverse of the square of the Jarlskog in matter ($1/{\hat{J}}^2$) is a fourth order polynomial in the matter potential which guarantees that it can be factored into two quadratics which immediately implies the functional form of our approximate, factorized expression.

   hep-phPRD(2019)·29 citations
10. 10*

    Thermally versus dynamically assisted Schwinger pair production

    Greger Torgrimsson🇩🇪

    We study electron-positron pair production by the combination of a strong, constant electric field and a thermal background. We show that this process is similar to dynamically assisted Schwinger pair production, where the strong field is instead assisted by another coherent field, which is weaker but faster. We treat the interaction with the photons from the thermal background perturbatively, while the interaction with the electric field is nonperturbative (i.e. a Furry picture expansion in $\alpha$). At $\mathcal{O}({\alpha }^2)$ we have ordinary perturbative Breit-Wheeler pair production assisted nonperturbatively by the electric field. Already at this order we recover the same exponential part of the probability as previous studies, which did not expand in $\alpha$. This means that we do not have to consider higher orders, so our approach allows us to calculate the pre-exponential part of the probability, which has not been obtained before in this regime. Although the prefactor is in general subdominant compared to the exponential part, in this case it can be important because it scales as ${\alpha }^2\ll 1$ and is therefore much smaller than the prefactor at $\mathcal{O}({\alpha }^0)$ (pure Schwinger pair production). We show that, because of the exponential enhancement, $\mathcal{O}({\alpha }^2)$ still gives the dominant contribution for temperatures above a certain threshold, but, because of the small prefactor, the threshold is higher than what the exponential alone would suggest.

    hep-phhep-thPRD(2019)·13 citations
11. 11*

    Isotropic charged cosmologies in infrared-modified electrodynamics

    Jorge F. Soriano🇺🇸 · Antonio L. Maroto🇪🇸

    It has long been known that the covariant formulation of quantum electrodynamics conflicts with the local description of states in the charged sector. Some of the solutions to this problem amount to modifications of the subsidiary conditions below some arbitrarily low photon frequency. Such infrared modified theories have been shown to be equivalent to standard Maxwell electrodynamics with an additional classical electromagnetic current induced by the quantum charges. The induced current only has support for very small frequencies and cancels the effects of the physical charges on large scales. In this work we explore the possibility that this de-electrification effect could allow for the existence of isotropic charged cosmologies, thus evading the stringent limits on the electric charge asymmetry of the universe. We consider a simple model of infrared-modified scalar electrodynamics in the cosmological context and find that the charged sector generates a new contribution to the energy-momentum tensor whose dominant contribution at late times is a cosmological constant-like term. If the charge asymmetry was generated during inflation, the limits on the asymmetry parameter in order not to produce a too-large cosmological constant are very stringent ${\eta }_Q<10^{-131}-10^{-144}$ for a number of e-folds $N=50-60$ in typical models. However if the charge imbalance is produced after inflation, the limits are relaxed in such a way that ${\eta }_Q<10^{-43}(100\text{mbox}GeV/T_Q)$, with $T_Q$ the temperature at which the asymmetry was generated. If the charge asymmetry has ever existed and the associated electromagnetic fields vanish in the asymptotic future, the limit can be further reduced to ${\eta }_Q<10^{-28}$.

    hep-phastro-ph.COgr-qcPRD(2019)·2 citations
12. 12*

    Scalar Democracy

    Christopher T. Hill🇺🇸 · Pedro A. N. Machado🇺🇸 · Anders E. Thomsen🇩🇰 · Jessica Turner🇺🇸

    We conjecture that there exists a scalar bound state for every pair of fundamental fermions at a UV (`composite') scale, $\Lambda \gg v_{\text{weak}}$. This implies a large number of universally coupled, sub-critical Higgs doublets. All but the Standard Model Higgs are `dormant,' with large positive squared masses and each receives a small vacuum expectation values via mixing with the Standard Model Higgs. Universal couplings, modulo renormalization group running effects, flips the flavor problem into the masses and mixings of the Higgs system. Doublets associated with heavy fermion masses, $b,c,\tau$ likely lie in the multi-TeV range, but may be observable at the current LHC, or a high-luminosity and/or an energy-upgraded LHC. In the lepton sector we are lead to a Higgs seesaw for neutrino masses, and corollary processes of observable flavor violation. The observation of the first sequential doublet coupled to $\bar{b}b$ with masses $\lesssim 3.5$ TeV would lend credence to the hypothesis.

    hep-phhep-exhep-thPRD(2019)·24 citations
13. 13*

    Equilibration of right-handed electrons

    Dietrich Bodeker🇩🇪 · Dennis Schroder🇩🇪

    We study the equilibration of right-handed electrons in the symmetric phase of the Standard Model. Due to the smallness of the electron Yukawa coupling, it happens relatively late in the history of the Universe. We compute the equilibration rate at leading order in the Standard Model couplings, by including gauge interactions, the top Yukawa- and the Higgs self-interaction. The dominant contribution is due to $2\to 2$ particle scattering, even though the rate of (inverse) Higgs decays is strongly enhanced by multiple soft scattering which is included by Landau-Pomeranchuk-Migdal (LPM) resummation. Our numerical result is substantially larger than approximations presented in previous literature.

    hep-phastro-ph.COJCAP(2019)·61 citations
14. 14*

    Measurement of b-hadron fractions in 13 TeV pp collisions

    LHCb Collaboration: R. Aaij🇳🇱 · C. Abellán Beteta🇨🇭 · B. Adeva🇪🇸 · M. Adinolfi🇬🇧 · C.A. Aidala🇺🇸 · Z. Ajaltouni🇫🇷 · S. Akar🇺🇸 · P. Albicocco🇮🇹 · J. Albrecht🇩🇪 · F. Alessio🇨🇭 · M. Alexander🇬🇧 · A. Alfonso Albero🇪🇸 and 835 other authors

    The production fractions of ${\overline{B}}_s^0$ and ${\Lambda }_b^0$ hadrons, normalized to the sum of $B^{-}$ and ${\overline{B}}^0$ fractions, are measured in 13 TeV pp collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67/fb. These ratios, averaged over the $b$-hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are $0.122\pm 0.006$ for ${\overline{B}}_s^0$, and $0.259\pm 0.018$ for ${\Lambda }_b^0$, where the uncertainties arise from both statistical and systematic sources. The ${\Lambda }_b^0$ ratio depends strongly on transverse momentum, while the ${\overline{B}}_s^0$ ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of $D^{+}$ to $D^0$ mesons produced in the sum of ${\overline{B}}^0$ and $B^{-}$ semileptonic decays is determined as $0.359\pm 0.006\pm 0.009$, where the uncertainties are statistical and systematic.

    ↳ hep-exhep-phPRD(2019)·242 citations
15. 15*

    Absence of Landau-Peierls Instability in the Magnetic Dual Chiral Density Wave Phase of Dense QCD

    Efrain J Ferrer🇺🇸 · Vivian de la Incera🇺🇸

    We investigate the stability of the Magnetic Dual Chiral Density Wave (MDCDW) phase of cold and dense QCD against collective low-energy fluctuations of the order parameter. The appearance of additional structures in the system free-energy due to the explicit breaking of the rotational and isospin symmetries by the external magnetic field and the field-induced asymmetry of the lowest Landau level modes play a crucial role in the analysis. The new structures not only affect the condensate minimum equations, but also the spectrum of the thermal fluctuations, which lacks the transverse soft modes that typically affect single-modulated inhomogeneous phases in the absence of a magnetic field. Consequently, the long-range order of the MDCDW phase is preserved at finite temperature. The lack of Landau-Peierls instabilities in the MDCDW phase makes this inhomogeneous phase of dense quark matter particularly relevant for the physics of neutron stars.

    ↳ nucl-thastro-ph.HEhep-phPRD(2020)·28 citations
16. 16*

    Observational status of the Galileon model general solution from cosmological data and gravitational waves

    Clément Leloup🇫🇷 · Vanina Ruhlmann-Kleider🇫🇷 · Jeremy Neveu🇫🇷 · Arnaud de Mattia🇫🇷

    The Galileon model is a tensor-scalar theory of gravity which explains the late acceleration of the Universe expansion with no instabilities and recovers General Relativity in the strong field limit. Most constraints obtained so far on Galileon model parameters from cosmological data were derived for the limited subset of tracker solutions and reported tensions between the model and data. This paper presents the first exploration of the general solution of the Galileon model, which is confronted against recent cosmological data for both background observables and linear perturbations, using Monte-Carlo Markov chains. As representative scenarios of the Galileon models, we study the full Galileon model with disformal coupling to matter and the uncoupled cubic Galileon model. We find that the general solution of the full Galileon model provides a good fit to CMB spectra, while the cubic Galileon model does not. When extending the comparison to BAO and SNIa data, even the general solution of the full Galileon model fails at providing a good fit to all datasets simultaneously. Tensions remain if the models are extended with an additional free parameter, such as the sum of active neutrino masses or the normalization of the CMB lensing spectrum. Finally, the multi-messenger observation of GW170817 is also discussed in the framework of the scenarios considered. The time delay between the gravitational signal and its electromagnetic counterpart was computed \textit{a posteriori} in every scenario of the full Galileon model cosmological fit chains and found to be ruled out by this observation.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2019)·13 citations
17. 17*

    Charmonium and exotics from lattice QCD

    Francesco Knechtli🇩🇪

    We review selected lattice results on the charmonium spectrum and first attempts to search for the existence of exotic states. The hadro-quarkonium model was proposed to interpret some of the exotic states as a quarkonium core inside a hadron. We present a lattice study of the hadro-quarkonium model in the limit of static quarks. The charm quark decouples in low energy observables and binding energies of charmonium. In a model calculation we are able to evaluate the corrections to decoupling of the charm quark in the continuum.

    ↳ hep-lathep-exhep-phEPJ Web Conf.(2019)·6 citations
18. 18*

    New paradigm for fluctuations in heavy-ion collisions

    Giuliano Giacalone🇫🇷 · Pablo Guerrero-Rodríguez🇪🇸 · Matthew Luzum🇧🇷 · Cyrille Marquet🇫🇷 · Jean-Yves Ollitrault🇫🇷

    Since their discovery, fluctuations in the initial state of heavy-ion collisions have been understood as originating mostly from the random positions of nucleons within the colliding nuclei. We consider an alternative approach where all the focus is on fluctuations generated by QCD interactions, that we evaluate at leading logarithmic accuracy in the color glass condensate effective theory. We validate our approach using BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) data on anisotropic flow. In particular, we show that, compared to standard Glauber-inspired calculations, our formalism provides a better description of the centrality dependence of the ratio of elliptic flow and triangular flow. It also naturally explains the evolution of elliptic flow fluctuations between RHIC and LHC energies.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2019)·35 citations
19. 19*

    Percent-Level Test of Isotropic Expansion Using Type Ia Supernovae

    John Soltis🇺🇸 · Arya Farahi🇺🇸 · Dragan Huterer🇺🇸 · C. Michael Liberato II🇺🇸

    We propose and implement a novel, robust, and non-parametric test of statistical isotropy of the expansion of the universe, and apply it to around one thousand type Ia supernovae from the Pantheon sample. We calculate the angular clustering of supernova magnitude residuals and compare it to the noise expected under the isotropic assumption. We also test for systematic effects and demonstrate that their effects are negligible or are already accounted for in our procedure. We express our constraints as an upper limit on the rms spatial variation in the Hubble parameter at late times. For the sky smoothed with a Gaussian with fwhm=60 deg, less than 1% rms spatial variation in the Hubble parameter is allowed at 99.7% confidence.

    ↳ astro-ph.COgr-qchep-phPRL(2019)·47 citations
20. 20*

    Massive On-Shell Supersymmetric Scattering Amplitudes

    Aidan Herderschee🇺🇸 · Seth Koren🇺🇸 · Timothy Trott🇺🇸

    We introduce a manifestly little group covariant on-shell superspace for massive particles in four dimensions using the massive spinor helicity formalism. This enables us to construct massive on-shell superfields and fully utilize on-shell symmetry considerations to derive all possible $\mathcal{N}=1$ three-particle amplitudes for particles of spin as high as one, as well as some simple amplitudes for particles of any spin. Throughout, the conceptual and computational simplicity of this approach is exhibited.

    ↳ hep-thhep-phJHEP(2019)·42 citations
21. 21*

    Constructing $\mathcal{N}=4$ Coulomb Branch Superamplitudes

    Aidan Herderschee🇺🇸 · Seth Koren🇺🇸 · Timothy Trott🇺🇸

    We study scattering amplitudes of massive BPS states on the Coulomb branch of $4d$ $\mathcal{N}=4$ super-Yang-Mills, utilising a little group covariant on-shell superspace for massive particles. Super-BCFW recursion for massive amplitudes is constructed and its validity is proven for all Coulomb branch superamplitudes. We then determine the exact three-particle superamplitudes for massive states. These ingredients allow us to explicitly compute the four- and five-particle superamplitudes, which is the first non-trivial usage of BCFW recursion for amplitudes with entirely massive external states. The manifest little group covariance helps clarify both the role of special kinematic properties of BPS states and the organizational structures of the superamplitudes.

    ↳ hep-thhep-phJHEP(2019)·52 citations
22. 22*

    Four-graviton scattering to three loops in $\mathcal{N}=8$ supergravity

    Johannes M. Henn🇩🇪 · Bernhard Mistlberger🇺🇸

    We compute the three-loop scattering amplitude of four gravitons in $\mathcal{N}=8$ supergravity. Our results are analytic formulae for a Laurent expansion of the amplitude in the regulator of dimensional regularisation. The coefficients of this series are closed formulae in terms of well-established harmonic poly-logarithms. Our results display a remarkable degree of simplicity and represent an important stepping stone in the exploration of the structure of scattering amplitudes. In particular, we observe that to this loop order the four graviton amplitude is given by uniform weight $2L$ functions, where $L$ is the loop order.

    ↳ hep-thhep-phJHEP(2019)·41 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.