Thu·Dec 22, 2016Thursday·December 22, 2016

1. 01*

   Majorana Higgses at colliders

   Miha Nemevšek🇸🇮 · Fabrizio Nesti🇮🇹 · Juan Carlos Vasquez🇨🇱

   Collider signals of heavy Majorana neutrino mass origin are studied in the minimal Left-Right symmetric model, where their mass is generated spontaneously together with the breaking of lepton number. The right-handed triplet Higgs boson $\Delta$, responsible for such breaking, can be copiously produced at the LHC through the Higgs portal in the gluon fusion and less so in gauge mediated channels. At $\Delta$ masses below the opening of the $VV$ decay channel, the two observable modes are pair-production of heavy neutrinos via the triplet gluon fusion $gg\to \Delta \to NN$ and pair production of triplets from the Higgs $h\to \Delta \Delta \to 4N$ decay. The latter features tri- and quad same-sign lepton final states that break lepton number by four units and have no significant background. In both cases up to four displaced vertices may be present and their displacement may serve as a discriminating variable. The backgrounds at the LHC, including the jet fake rate, are estimated and the resulting sensitivity to the Left-Right breaking scale extends well beyond 10 TeV. In addition, sub-dominant radiative modes are surveyed: the $\gamma \gamma$, $Z\gamma$ and lepton flavour violating ones. Finally, prospects for $\Delta$ signals at future $e^{+}{e}^{-}$ colliders are presented.

   hep-phhep-exJHEP(2017)·85 citations
2. 02*

   $(g-2{)}_{\mu }$, Lepton Flavour Violation and $Z$ Decays with Leptoquarks: Correlations and Future Prospects

   Estefania Coluccio Leskow🇮🇹 · Andreas Crivellin🇨🇭 · Giancarlo D'Ambrosio🇮🇹 · Dario Müller🇨🇭

   The long-standing anomaly in the anomalous magnetic moment of the muon indicates the presence of chirality violating new physics contributions. A possible solution involves scalar leptoquarks with left- and right-handed couplings to the top quark. Two such representations of scalar leptoquarks exist for which the contribution to $(g-2{)}_{\mu }$ can possess an $m_t/m_{\mu }$ enhancement compared to the Standard Model. The leptoquarks also induce loop corrections to $Z$ couplings to muons which probe as well new physics contributions which possess sources of $SU(2)$ symmetry breaking and we find that this effect should be observable at future experiments as GigaZ or TLEP. Furthermore, once interactions of the leptoquark with tau leptons and electrons are present, additional correlated effects in anomalous magnetic moments, $Z\to \ell {\ell }^{\prime }$ and $\ell \to {\ell }^{\prime }\gamma$ arise, which can be used to test the model and to determine the flavour structure of the couplings. We find that the two representations of leptoquarks can be distinguished also from low energy experiments: one representation predicts constructive interference with the Standard Model in $Z$ couplings to leptons and effects in $B\to K^{(\star )}\nu \bar{\nu }$, while the other representation interferes destructively with the Standard Model in $Z$ couplings to leptons and gives a $C_9=C_{10}$-like contribution to $b\to s{\ell }^{+}{\ell }^{-}$ processes.

   hep-phhep-exPRD(2017)·128 citations
3. 03*

   A frame independent classification of single field inflationary models

   Laur Järv🇪🇪 · Kristjan Kannike🇪🇪 · Luca Marzola🇪🇪 · Antonio Racioppi🇪🇪 · Martti Raidal🇪🇪 · Mihkel Rünkla🇪🇪 · Margus Saal🇪🇪 · Hardi Veermäe🇪🇪

   Seemingly unrelated models of inflation that originate from different physical setups yield, in some cases, identical predictions for the currently constrained inflationary observables. In order to classify the available models, we propose to express the slow-roll parameters and the relevant observables in terms of frame and reparametrisation invariant quantities. The adopted invariant formalism makes manifest the redundancy that afflicts the current description of inflation dynamics and offers a straightforward way to identify classes of models which yield identical phenomenology. In this Letter we offer a step-to-step recipe to recast every single field inflationary model in the proposed formalism, detailing also the procedure to compute inflationary observables in terms of frame and reparametrisation invariant quantities. We hope that our results become the cornerstone of a new categorisation of viable inflationary models and open the way to a deeper understanding of the inflation mechanism.

   hep-phastro-ph.COgr-qcPRL(2017)·94 citations
4. 04*

   Dark Matter "Collider" from Inelastic Boosted Dark Matter

   Doojin Kim🇺🇸 · Jong-Chul Park🇰🇷 · Seodong Shin🇺🇸

   We propose a novel dark matter (DM) detection strategy for the models with non-minimal dark sector. The main ingredients in the underlying DM scenario are a boosted DM particle and a heavier dark sector state. The relativistic DM impinged on target material scatters off inelastically to the heavier state which subsequently decays into DM along with lighter states including visible (Standard Model) particles. The expected signal event, therefore, accompanies a visible signature by the secondary cascade process associated with a recoiling of the target particle, differing from the typical neutrino signal not involving the secondary signature. We then discuss various kinematic features followed by DM detection prospects at large volume neutrino detectors with a model framework where a dark gauge boson is the mediator between the Standard Model particles and DM.

   hep-phhep-exPRL(2017)·88 citations
5. 05*

   Geometric phases in neutrino oscillations with nonlinear refraction

   Lucas Johns🇺🇸 · George M. Fuller🇺🇸

   Neutrinos propagating in dense astrophysical environments sustain nonlinear refractive effects due to neutrino-neutrino forward scattering. We study geometric phases in neutrino oscillations that arise out of cyclic evolution of the potential generated by these forward-scattering processes. We perform several calculations, exact and perturbative, that illustrate the robustness of such phases, and of geometric effects more broadly, in the flavor evolution of neutrinos. The scenarios we consider are highly idealized in order to make them analytically tractable, but they suggest the possible presence of complicated geometric effects in realistic astrophysical settings. We also point out that in the limit of extremely high neutrino densities, the nonlinear potential in three flavors naturally gives rise to non-Abelian geometric phases. This paper is intended to be accessible to neutrino experts and non-specialists alike.

   hep-phastro-ph.COastro-ph.HEquant-phPRD(2017)·19 citations
6. 06*

   Anomalous Chiral Transport in Heavy Ion Collisions

   Jinfeng Liao🇺🇸

   Chiral anomaly is a very fundamental aspect of quantum theories with chiral fermion, from the Standard Model to supersymmetric field theories or even string theories. How such microscopic anomaly manifests itself in a macroscopic many-body system with chiral fermions, is a highly nontrivial question that has recently attracted significant interest. As it turns out, unusual transport currents can be induced by chiral anomaly under suitable conditions in such systems, with the notable example of the Chiral Magnetic Effect (CME) where a vector current (e.g. electric current) is generated along an external magnetic field. The CME has been enthusiastically studied in two very different physical systems: the Dirac and Weyl semimetals in condensed matter physics as well as the quark-gluon plasma in heavy ion collisions. In this contribution, we report the latest theoretical and experimental status for the search of CME in heavy ion collisions.

   hep-phcond-mat.mes-hallhep-thnucl-ex+1PoS(2016)·0 citations
7. 07*

   Probing a dark photon using rare leptonic kaon and pion decays

   Cheng-Wei Chiang🇹🇼 · Po-Yan Tseng🇯🇵

   Rare leptonic kaon and pion decays $K^{+}({\pi }^{+})\to {\mu }^{+}{\nu }_{\mu }{e}^{+}{e}^{-}$ can be used to probe a dark photon of mass $\mathcal{O}(10)$~MeV, with the background coming from the mediation of a virtual photon. This is most relevant for the 16.7-MeV dark photon proposed to explain a 6.8$\sigma$ anomaly recently observed in ${}^8$Be transitions by the Atomki Collaboration. We evaluate the reach of future experiments for different scenarios of how the dark photon couples with the standard model particles, and show that a great portion of the preferred 16.7-MeV dark photon parameter space can be decisively probed. We also show the use of angular distributions to further distinguish the signal from the background.

   hep-phPLB(2017)·41 citations
8. 08*

   Physics reach of MoEDAL at LHC: magnetic monopoles, supersymmetry and beyond

   Nick E. Mavromatos🇬🇧 · Vasiliki A. Mitsou (for the MoEDAL Collaboration)🇪🇸

   MoEDAL is a pioneering experiment designed to search for highly ionising messengers of new physics such as magnetic monopoles or massive (pseudo-)stable charged particles, that are predicted to exist in a plethora of models beyond the Standard Model. Its ground-breaking physics program defines a number of scenarios that yield potentially revolutionary insights into such foundational questions as, are there extra dimensions or new symmetries, what is the mechanism for the generation of mass, does magnetic charge exist, what is the nature of dark matter, and, how did the big-bang develop at the earliest times. MoEDAL's purpose is to meet such far-reaching challenges at the frontier of the field. The physics reach of the existing MoEDAL detector is discussed, giving emphasis on searches for magnetic monopoles, supersymmetric (semi)stable partners, doubly charged Higgs bosons, and exotic structures such as black-hole remnants in models with large extra spatial dimensions and D-matter in some brane theories.

   hep-phEPJ Web Conf.(2017)·21 citations
9. 09*

   Quantized vortex rings in superfluid He4 and Light Dark Matter

   Massimo Cerdonio🇮🇹

   The possibility is considered that, after nuclear recoil caused by elastic scattering with Light Dark Matter, atoms in superfluid He4 may create quantized vortex rings, which can thereafter be detected. The concept for sort of telescope for LDM is presented, which would be sensitive to its motion through the Galactic LDM wind. A demonstrator is proposed, which makes use of thermal neutrons.

   hep-phcond-mat.othergr-qc1 citation
10. 10*

    Dielectric Haloscopes to Search for Axion Dark Matter: Theoretical Foundations

    Alexander J. Millar🇩🇪 · Georg G. Raffelt🇩🇪 · Javier Redondo🇪🇸 · Frank D. Steffen🇩🇪

    We study the underlying theory of dielectric haloscopes, a new way to detect dark matter axions. When an interface between different dielectric media is inside a magnetic field, the oscillating axion field acts as a source of electromagnetic waves, which emerge in both directions perpendicular to the surface. The emission rate can be boosted by multiple layers judiciously placed to achieve constructive interference and by a large transverse area. Starting from the axion-modified Maxwell equations, we calculate the efficiency of this new dielectric haloscope approach. This technique could potentially search the unexplored high-frequency range of 10--100 GHz (axion mass 40--400 $\mu$eV), where traditional cavity resonators have difficulties reaching the required volume.

    hep-phastro-ph.COastro-ph.HEhep-ex+1JCAP(2017)·149 citations
11. 11*

    Supergravity Contributions to Inflation in models with non-minimal coupling to gravity

    Kumar Das🇮🇳 · Valerie Domcke🇫🇷 · Koushik Dutta🇮🇳

    This paper provides a systematic study of supergravity contributions relevant for inflationary model building in Jordan frame supergravity. In this framework, canonical kinetic terms in the Jordan frame result in the separation of the Jordan frame scalar potential into a tree-level term and a supergravity contribution, which is potentially dangerous for sustaining inflation. We show that if the vacuum energy necessary for driving inflation originates dominantly from the F-term of an auxiliary field (i.e. not the inflaton), the supergravity corrections to the Jordan frame scalar potential are generically suppressed. Moreover, these supergravity contributions identically vanish if the superpotential $W$ vanishes along the inflationary trajectory. On the other hand, if the F-term associated with the inflaton dominates the vacuum energy, the supergravity contributions are generically comparable to the globally supersymmetric contributions. In addition, the non-minimal coupling to gravity inherent to Jordan frame supergravity significantly impacts the inflationary model depending on the size and sign of this coupling. We discuss the phenomenology of some representative inflationary models, and point out the relation to the recently much discussed cosmological `attractor' models.

    hep-phastro-ph.COhep-thJCAP(2017)·4 citations
12. 12*

    Thermal shifts, fluctuations, and missing states

    Enrique Ruiz Arriola🇪🇸 · Wojciech Broniowski🇵🇱 · Eugenio Megias🇪🇸 · Lorenzo L. Salcedo🇪🇸

    Thermal shifts and fluctuations at finite temperature below the deconfinement crossover from hadronic matter to the quark-gluon plasma provide a viable way to search for missing states with given quantum numbers in the hadronic spectrum. We analyze three realizations of the hadron resonance gas model in the light quark (uds) sector: the states from the Particle Data Group tables with or without width and from the Relativized Quark Model. We elaborate on the meaning of hadronic completeness and thermodynamical equivalence on the light of lattice QCD trace anomaly, heavy quark entropy shift and baryon,charge and strangeness susceptibilities.

    hep-phhep-latnucl-th6 citations
13. 13*

    Saving the MSSM from the Galactic Center Excess

    Anja Butter🇩🇪 · Simona Murgia🇺🇸 · Tilman Plehn🇩🇪 · Tim M.P. Tait🇺🇸

    The minimal supersymmetric setup offers a comprehensive framework to interpret the Fermi LAT Galactic center excess. Taking into account experimental, theoretical, and astrophysical uncertainties we can identify valid parameter regions linked to different annihilation channels. They extend to dark matter masses above 250 GeV. There exists a very mild tension between the observed relic density and the annihilation rate in the center of our galaxy for specific channels. The strongest additional constraints come from the new generation of direct detection experiments, ruling out much of the light and intermediate dark matter mass regime and giving preference to heavier dark matter annihilating into a pair of top quarks.

    hep-phPRD(2017)·19 citations
14. 14*

    A perturbative QCD approach to ${\pi }^{-}p\to D^{-}{\Lambda }_c^{+}$

    S. Kofler🇦🇹 · W. Schweiger🇦🇹

    We employ the generalized parton picture to analyze the reaction ${\pi }^{-}p\to D^{-}{\Lambda }_c^{+}$. Thereby it is assumed that the process amplitude factorizes into one for the perturbatively calculable subprocess $\bar{u}u\to \bar{c}c$ and hadronic matrix elements that can be parameterized in terms of generalized parton distributions for the ${\pi }^{-}\to D^{-}$ and $p\to {\Lambda }_c^{+}$ transitions, respectively. Representing these parton distributions in terms of valence-quark light-cone wave functions for $\pi$, $D$, $p$ and ${\Lambda }_c$ allows us to make numerical predictions for unpolarized differential and integrated cross sections as well as spin observables. In the kinematical region where this approach is supposed to work, i.e. $s\gtrsim 20$~GeV${}^2$ and in the forward hemisphere, the resulting cross sections are of the order of nb. This is a finding that could be of interest in view of plans to measure ${\pi }^{-}p\to D^{-}{\Lambda }_c^{+}$, e.g., at J-PARC or COMPASS.

    hep-phFew Body Syst.(2017)·0 citations
15. 15*

    Low Fine Tuning in Yukawa-deflected Gauge Mediation

    Waqas Ahmed🇨🇳 · Lorenzo Calibbi🇨🇳 · Tianjun Li🇨🇳 · Azar Mustafayev🇺🇸 · Shabbar Raza🇨🇳

    We discuss a class of models with gauge-mediated supersymmetry breaking characterized by a non-unified messenger sector inducing non-standard gaugino mass ratios, as well as by additional contributions to the soft mass terms from a matter-messenger coupling. The well-known effect of this coupling is to generate A-terms at one-loop level, hence raising the Higgs mass without relying on super-heavy stops. At the same time, a hierarchy between Wino and gluino masses, as induced by the non-unified messenger fields, can greatly lower the radiative corrections to the Higgs soft mass term driven by the high-energy parameters, thus reducing the fine tuning. We search for models with low fine tuning within this scenario, and we discuss the spectrum, collider phenomenology, constraints, and prospects of the found solutions. We find that some setups are accessible or already excluded by searches at the Large Hadron Collider, and all our scenarios with a tuning better than about 2\% can be tested at the International Linear Collider.

    hep-phPRD(2017)·7 citations
16. 16*

    Higgs production in association with off-shell top-antitop pairs at NLO EW and QCD at the LHC

    Ansgar Denner🇩🇪 · Jean-Nicolas Lang🇩🇪 · Mathieu Pellen🇩🇪 · Sandro Uccirati🇮🇹

    We present NLO electroweak corrections to Higgs production in association with off-shell top-antitop quark pairs. The full process $\text{p}\text{p}\to {\text{e}}^{+}{\nu }_{\text{e}}{\mu }^{-}{\bar{\nu }}_{\mu }\text{b}\bar{\text{b}}\text{H}$ is considered, and hence all interference, off-shell, and non-resonant contributions are taken into account. The electroweak corrections turn out to be below one per cent for the integrated cross section but can exceed $10\%$ in certain phase-space regions. In addition to its phenomenological relevance, the computation constitutes a major technical achievement as the full NLO virtual corrections involving up to 9-point functions have been computed exactly. The results of the full computation are supported by two calculations in the double-pole approximation. These also allow to infer the effect of off-shell contributions and emphasise their importance especially for the run II of the LHC. Finally, we present combined predictions featuring both NLO electroweak and QCD corrections in a common set-up that will help the experimental collaborations in their quest of precisely measuring the aforementioned process.

    hep-phhep-exJHEP(2017)·82 citations
17. 17*

    Unification and Local Baryon Number

    Pavel Fileviez Perez🇺🇸 · Sebastian Ohmer🇩🇪

    We investigate the possibility to find an ultraviolet completion of the simple extensions of the Standard Model where baryon number is a local symmetry. In the context of such theories one can understand the spontaneous breaking of baryon number at the low scale and the proton stability. We find a simple theory based on SU(4)_C x SU(3)_L x SU(3)_R where baryon number is embedded in a non-Abelian gauge symmetry. We discuss the main features of the theory and the possible implications for experiments. This theory predicts stable colored and/or fractional electric charged fields which can give rise to very exotic signatures at the Large Hadron Collider experiments such as CMS and ATLAS. We further discuss the embedding in a gauge theory based on SU(4)_C x SU(4)_L x SU(4)_R which could define the way to achieve the unification of the gauge interactions at the low scale.

    hep-phhep-exhep-thPLB(2017)·13 citations
18. 18*

    Light neutral CP-even Higgs boson within Next-to-Minimal Supersymmetric Standard model (NMSSM) at the Large Hadron electron Collider (LHeC)

    Siba Prasad Das🇨🇴 · Marek Nowakowski🇨🇴

    We analyze the prospects of observing the light CP-even neutral Higgs bosons ($h_1$) in their decays into $b\bar{b}$ quarks, in the neutral and charged current production processes $e{h}_{1}q$ and $\nu h_{1}q$ at the upcoming LHeC, with $\sqrt{s}\approx 1.296$ TeV. Assuming that the intermediate Higgs boson ($h_2$) is Standard Model (SM)-like, we study the Higgs production within the framework of NMSSM. We consider the constraints from Dark-matter, Sparticle masses, and the Higgs boson data. The signal in our analysis can be classified as three jets, with electron (missing energy)coming from the neutral (charged) current interaction. We demand that the number of b-tagged jets in the central rapidity region be greater or equal to two. The remaining jet is tagged in the forward regions. With this forward jet and two $b$-tagged jets in the central region, we reconstructed three jets invariant masses. Applying some lower limits on these invariant masses turns out to be an essential criterion to enhance the signal--to--background rates, with slightly different sets of kinematical selections in the two different channels. We consider almost all reducible and irreducible SM background processes. We find that the non-SM like Higgs boson, $h_1$, would be accessible in some of the NMSSM benchmark points, at approximately 0.4$\sigma$ (2.5$\sigma$) level in the $e$+3j channel up to Higgs boson masses of 75 GeV and in the $E{/}_T$+3j channel could be discovered with 1.7$\sigma$ (2.4$\sigma$) level up to Higgs boson masses of 88 GeV with 100 fb${}^{-1}$ of data in a simple cut-based (with optimization) selection. With ten times more data accumulation at the end of the LHeC run and using optimization, one can have 5$\sigma$ discovery in the electron (missing energy) channel up to 85 (more than 90) GeV.

    hep-phhep-exPRD(2017)·23 citations
19. 19*

    Quarkonium suppression in heavy-ion collisions: an open quantum system approach

    Nora Brambilla🇩🇪 · Miguel A. Escobedo🇫🇮 · Joan Soto🇪🇸 · Antonio Vairo🇩🇪

    We address the evolution of heavy-quarkonium states in an expanding quark-gluon plasma by implementing effective field theory techniques in the framework of open quantum systems. In this setting we compute the nuclear modification factors for quarkonia that are $S$-wave Coulombic bound states in a strongly-coupled quark-gluon plasma. The calculation is performed at an accuracy that is leading-order in the heavy-quark density expansion and next-to-leading order in the multipole expansion. The quarkonium density-matrix evolution equations can be written in the Lindblad form, and, hence, they account for both dissociation and recombination. Thermal mass shifts, thermal widths and the Lindblad equation itself depend on only two non-perturbative parameters: the heavy-quark momentum diffusion coefficient and its dispersive counterpart. Finally, by numerically solving the Lindblad equation, we provide results for the ${\rm Y}(1S)$ and ${\rm Y}(2S)$ suppression.

    hep-phhep-exnucl-thPRD(2017)·214 citations
20. 20*

    The matrix element method at next-to-leading order for arbitrary jet algorithms

    Robin Baumeister🇩🇪 · Stefan Weinzierl🇩🇪

    The matrix element method usually employs leading-order matrix elements. We discuss the generalisation towards higher orders in perturbation theory and show how the matrix element method can be used at next-to-leading order for arbitrary infrared-safe jet algorithms. We discuss three variants at next-to-leading order. The first two variants work at the level of the jet momenta. The first variant adheres to strict fixed-order in perturbation theory. We present a method for the required integration over the radiation phase space. The second variant is inspired by the POWHEG method and works as the first variant at the level of the jet momenta. The third variant is a more exclusive POWHEG version. Here we resolve exactly one jet into two sub-jets. If the two sub-jets are resolved above a scale $p_{\perp }^{\min }$, the likelihood is computed from the POWHEG-modified real emission part, otherwise it is given by the POWHEG-modified virtual part.

    hep-phPRD(2017)·12 citations
21. 21*

    Sensitivities and synergies of DUNE and T2HK

    Peter Ballett🇬🇧 · Stephen F. King🇬🇧 · Silvia Pascoli🇬🇧 · Nick W. Prouse🇬🇧 · TseChun Wang🇬🇧

    Long-baseline neutrino oscillation experiments, in particular Deep Underground Neutrino Experiment (DUNE) and Tokai to Hyper-Kamiokande (T2HK), will lead the effort in the precision determination of the as yet unknown parameters of the leptonic mixing matrix. In this article, we revisit the potential of DUNE, T2HK and their combination in light of the most recent experimental information. As well as addressing more conventional questions, we pay particular attention to the attainable precision on {\delta}, which is playing an increasingly important role in the physics case of the long-baseline programme. We analyse the complementarity of the two designs, identify the benefit of a programme comprising distinct experiments and consider how best to optimise the global oscillation programme. This latter question is particularly pertinent in light of a number of alternative design options which have recently been mooted: a Korean second detector for T2HK and different beams options at DUNE. We study the impact of these options and quantify the synergies between alternative proposals, identifying the best means of furthering our knowledge of the fundamental physics of neutrino oscillation.

    hep-phPRD(2017)·65 citations
22. 22*

    Diffeomorphism-invariant averaging in quantum gravity and cosmology

    Anthony W. H. Preston🇬🇧

    This thesis concerns research undertaken in two related topics concerning high-energy gravitational physics. The first is the construction of a manifestly diffeomorphism-invariant Exact Renormalization Group (ERG). This is a procedure that constructs effective theories of gravity by integrating out high-energy modes down to an ultraviolet cutoff scale without gauge-fixing. The manifest diffeomorphism invariance enables us to construct a fully background-independent formulation. This thesis will explore both the fixed-background and background-independent forms of the manifestly diffeomorphism-invariant ERG. The second topic is cosmological backreaction, which concerns the effect of averaging over high-frequency metric perturbations to the gravitational field equations describing the universe at large scales. This has been much studied the context of the unmodified form of General Relativity, but has been much less studied in the context of higher-derivative effective theories obtained by integrating out the high-energy modes of some more fundamental (quantum) theory of gravity. The effective stress-energy tensor for backreaction can be used directly as a diffeomorphism-invariant effective stress-energy tensor for gravitational waves without specifying the background metric. This thesis will construct the manifestly diffeomorphism-invariant ERG and compute the effective action at the classical level in two different schemes. We will then turn to cosmological backreaction in higher-derivative gravity, deriving the general form of the effective stress-energy tensor due to inhomogeneity for local diffeomorphism-invariant effective theories of gravity. This an exciting research direction, as it begins the construction of a quantum theory of gravity as well as investigating possible implications for cosmology.

    ↳ gr-qcastro-ph.COhep-phhep-th0 citations
23. 23*

    Neutral-Current Weak Interactions at an EIC

    Y. X. Zhao🇺🇸 · A. Deshpande🇺🇸 · J. Huang🇺🇸 · K. S. Kumar🇺🇸 · S. Riordan🇺🇸

    A simulation study of measurements of neutral current structure functions of the nucleon at the future high-energy and high-luminosity polarized electron-ion collider (EIC) is presented. A new series of $\gamma -Z$ interference structure functions, $F_1^{\gamma Z}$, $F_3^{\gamma Z}$, $g_1^{\gamma Z}$, $g_5^{\gamma Z}$ become accessible via parity-violating asymmetries in polarized electron-nucleon deep inelastic scattering (DIS). Within the context of the quark-parton model, they provide a unique and, in some cases, yet-unmeasured combination of unpolarized and polarized parton distribution functions. The uncertainty projections for these structure functions using electron-proton collisions are considered for various EIC beam energy configurations. Also presented are uncertainty projections for measurements of the weak mixing angle ${\sin }^2{\theta }_W$ using electron-deuteron collisions which cover a much higher $Q^2$ than that is accessible in fixed target measurements. QED and QCD radiative corrections and effects of detector smearing are included with the calculations.

    ↳ nucl-exhep-exhep-phEPJA(2017)·26 citations
24. 24*

    On the Feynman-Hellmann Theorem in Quantum Field Theory and the Calculation of Matrix Elements

    Chris Bouchard🇺🇸 · Chia Cheng Chang🇺🇸 · Thorsten Kurth🇺🇸 · Kostas Orginos🇺🇸 · Andre Walker-Loud🇺🇸

    The Feynman-Hellmann theorem can be derived from the long Euclidean-time limit of correlation functions determined with functional derivatives of the partition function. Using this insight, we fully develop an improved method for computing matrix elements of external currents utilizing only two-point correlation functions. Our method applies to matrix elements of any external bilinear current, including nonzero momentum transfer, flavor-changing, and two or more current insertion matrix elements. The ability to identify and control all the systematic uncertainties in the analysis of the correlation functions stems from the unique time dependence of the ground-state matrix elements and the fact that all excited states and contact terms are Euclidean-time dependent. We demonstrate the utility of our method with a calculation of the nucleon axial charge using gradient-flowed domain-wall valence quarks on the $N_f=2+1+1$ MILC highly improved staggered quark ensemble with lattice spacing and pion mass of approximately 0.15 fm and 310 MeV respectively. We show full control over excited-state systematics with the new method and obtain a value of $g_A=1.213(26)$ with a quark-mass-dependent renormalization coefficient.

    ↳ hep-lathep-phnucl-thPRD(2017)·95 citations
25. 25*

    Electromagnetic instability and Schwinger effect in the Witten-Sakai-Sugimoto model with D0-D4 background

    Wenhe Cai🇨🇳 · Kang-le Li🇨🇳 · Si-wen Li🇨🇳

    Using the Witten-Sakai-Sugimoto model in the D0-D4 background, we holographically compute the vacuum decay rate of the Schwinger effect in this model. Our calculation contains the influence of the D0-brane density which could be identified as the $\theta$ angle or chiral potential in QCD. Under the strong electromagnetic fields, the instability appears due to the creation of quark-antiquark pairs and the associated decay rate can be obtained by evaluating the imaginary part of the effective Euler-Heisenberg action which is identified as the action of the probe brane with a constant electromagnetic field. In the bubble D0-D4 configuration, we find the decay rate decreases when the $\theta$ angle increases since the vacuum becomes heavier in the present of the glue condensate in this system. And the decay rate matches to the result in the black D0-D4 configuration at zero temperature limit according to our calculations. In this sense, the Hawking-Page transition of this model could be consistently interpreted as the confined/deconfined phase transition. Additionally there is another instability from the D0-brane itself in this system and we suggest that this instability reflects to the vacuum decay triggered by the $\theta$ angle as it is known in the $\theta$-dependent QCD.

    ↳ hep-thhep-phEPJC(2019)·11 citations
26. 26*

    Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016

    Heavy Flavor Averaging Group (HFLAV) · Y. Amhis · Sw. Banerjee · E. Ben-Haim · F. Bernlochner · A. Bozek · C. Bozzi · M. Chrząszcz · J. Dingfelder · S. Duell · M. Gersabeck · T. Gershon and 32 other authors

    This article reports world averages of measurements of $b$-hadron, $c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, \CP~violation parameters, parameters of semileptonic decays and CKM matrix elements.

    ↳ hep-exhep-phEPJC(2017)·1203 citations
27. 27*

    Massive Fermi Gas in the Expanding Universe

    Andreas Trautner🇩🇪

    The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.

    ↳ astro-ph.COcond-mat.quant-gashep-phquant-phJCAP(2017)·9 citations
28. 28*

    An Addendum to the Heisenberg-Euler effective action beyond one loop

    Holger Gies🇩🇪 · Felix Karbstein🇩🇪

    We study the effective interactions of external electromagnetic fields induced by fluctuations of virtual particles in the vacuum of quantum electrodynamics. Our main focus is on these interactions at two-loop order. We discuss in detail the emergence of the renowned Heisenberg-Euler effective action from the underlying microscopic theory of quantum electrodynamics, emphasizing its distinction from a standard one-particle irreducible effective action. In our explicit calculations we limit ourselves to constant and slowly varying external fields, allowing us to adopt a locally constant field approximation. One of our main findings is that at two-loop order there is a finite one-particle reducible contribution to the Heisenberg-Euler effective action in constant fields, which was previously assumed to vanish. In addition to their conceptual significance, our results are relevant for high-precision probes of quantum vacuum nonlinearity in strong electromagnetic fields.

    ↳ hep-thhep-phJHEP(2017)·104 citations

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