Tue·Nov 8, 2016Tuesday·November 8, 2016

1. 01*

   Updated fit to three neutrino mixing: exploring the accelerator-reactor complementarity

   Ivan Esteban🇪🇸 · M. C. Gonzalez-Garcia🇪🇸 · Michele Maltoni🇪🇸 · Ivan Martinez-Soler🇪🇸 · Thomas Schwetz🇩🇪

   We perform a combined fit to global neutrino oscillation data available as of fall 2016 in the scenario of three-neutrino oscillations and present updated allowed ranges of the six oscillation parameters. We discuss the differences arising between the consistent combination of the data samples from accelerator and reactor experiments compared to partial combinations. We quantify the confidence in the determination of the less precisely known parameters ${\theta }_{23}$, ${\delta }_{\text{CP}}$, and the neutrino mass ordering by performing a Monte Carlo study of the long baseline accelerator and reactor data. We find that the sensitivity to the mass ordering and the ${\theta }_{23}$ octant is below $1\sigma$. Maximal ${\theta }_{23}$ mixing is allowed at slightly more than 90% CL. The best fit for the CP violating phase is around $270^{\circ }$, CP conservation is allowed at slightly above $1\sigma$, and values of ${\delta }_{\text{CP}}\simeq 90^{\circ }$ are disfavored at around 99% CL for normal ordering and higher CL for inverted ordering.

   hep-phhep-exJHEP(2017)·740 citations
2. 02*

   Sterile Neutrino Dark Matter with Supersymmetry

   Bibhushan Shakya🇺🇸 · James D. Wells🇺🇸

   Sterile neutrino dark matter, a popular alternative to the WIMP paradigm, has generally been studied in non-supersymmetric setups. If the underlying theory is supersymmetric, we find that several interesting and novel dark matter features can arise. In particular, in scenarios of freeze-in production of sterile neutrino dark matter, its superpartner, the sterile sneutrino, can play a crucial role in early Universe cosmology as the dominant source of cold, warm, or hot dark matter, or of a subdominant relativistic population of sterile neutrinos that can contribute to the effective number of relativistic degrees of freedom Neff during Big Bang nucleosynthesis.

   hep-phastro-ph.COPRD(2017)·28 citations
3. 03*

   Nonlocal wave turbulence in non-Abelian plasmas

   Yacine Mehtar-Tani🇺🇸

   We investigate driven wave turbulence in non-Abelian plasmas, in the framework of kinetic theory where both elastic and inelastic processes are considered in the small angle approximation. The gluon spectrum, that forms in the presence of a steady source, is shown to be controlled by nonlocal interactions in momentum space, in contrast to the universal Kolmogorov-Zakharov spectra. Assuming strongly nonlocal interactions, we show that inelastic processes are dominant in the IR and cause a thermal bath to form below the forcing scale, as a result of a detailed balance between radiation and absorption of soft gluons by the hard ones. Above the forcing scale, the inelastic collision term reduces to an inhomogeneous diffusion-like equation yielding a spectrum that spreads to the UV as $t^{1/2}$, similarly to elastic processes. Due to nonlocal interactions the non-universal turbulent spectrum is not steady and flattens when time goes on toward the thermal distribution. This analysis is complemented by numerical simulations, where we observe that in the explored time interval the spectral exponent of the nonlocal turbulent cascade is close to $-2$ in agreement with simulations of classical Yang-Mills equations.

   hep-phnlin.CDnucl-thNPA(2017)·4 citations
4. 04*

   Phenomenological Review on Quark-Gluon Plasma: Concepts vs. Observations

   Roman Pasechnik🇸🇪 · Michal Šumbera🇨🇿

   In this review, we present an up-to-date phenomenological summary of research developments in the physics of the Quark--Gluon Plasma (QGP). A short historical perspective and theoretical motivation for this rapidly developing field of contemporary particle physics is provided. In addition, we introduce and discuss the role of the quantum chromodynamics (QCD) ground state, non-perturbative and lattice QCD results on the QGP properties, as well as the transport models used to make a connection between theory and experiment. The experimental part presents the selected results on bulk observables, hard and penetrating probes obtained in the ultra-relativistic heavy-ion experiments carried out at the Brookhaven National Laboratory Relativistic Heavy Ion Collider (BNL RHIC) and CERN Super Proton Synchrotron (SPS) and Large Hadron Collider (LHC) accelerators. We also give a brief overview of new developments related to the ongoing searches of the QCD critical point and to the collectivity in small ($p+p$ and $p+A$) systems.

   hep-phhep-exnucl-thUniverse(2017)·215 citations
5. 05*

   Coupling of $t\bar{t}$ and $\gamma \gamma$ with a strongly interacting Electroweak Symmetry Breaking Sector

   Rafael L. Delgado🇪🇸

   We report the coupling of an external $\gamma \gamma$ or $t\bar{t}$ state to a strongly interacting EWSBS satisfying unitarity. We exploit perturbation theory for those coupling of the external state, whereas the EWSBS is taken as strongly interacting. We use a modified version of the IAM unitarization procedure to model such a strongly interacting regime. The matrix elements $V_L{V}_L\to V_L{V}_L$, $V_L{V}_L\leftrightarrow hh$, $hh\to hh$, $V_L{V}_L\leftrightarrow \{\gamma \gamma ,t\bar{t}\}$, and $hh\leftrightarrow \{\gamma \gamma ,t\bar{t}\}$ are all computed to NLO in perturbation theory with the Nonlinear Effective Field Theory of the EWSBS, within the Equivalence Theorem. This allows us to describe resonances of the electroweak sector that may be found at the LHC and their effect on other channels such as $\gamma \gamma$ or $t\bar{t}$ where they may be discovered.

   hep-phEPJ Web Conf.(2017)·0 citations
6. 06*

   Calculations of the dominant long-range, spin-independent contributions to the interaction energy between two nonrelativistic Dirac fermions from double-boson exchange of spin-0 and spin-1 bosons with spin-dependent couplings

   S. Aldaihan🇺🇸 · D. E. Krause🇺🇸 · J. C. Long🇺🇸 · W. M. Snow🇺🇸

   Various theories beyond the Standard Model predict new particles with masses in the sub-eV range with very weak couplings to ordinary matter which can possess spin-dependent couplings to electrons and nucleons. Present laboratory constraints on exotic spin-dependent interactions with pseudoscalar and axial couplings for exchange boson masses between meV and eV are very poor compared to constraints on spin-independent interactions in the same mass range arising from spin-0 and spin-1 boson exchange. It is therefore interesting to analyze in a general way how one can use the strong experimental bounds on spin-independent interactions to also constrain spin-dependent interactions by considering higher-order exchange processes. The exchange of a pair of bosons between two fermions with spin-dependent couplings will possess contributions which flip spins twice and thereby generate a polarization-independent interaction energy which can add coherently between two unpolarized objects. In this paper we derive the dominant long-range contributions to the interaction energy between two nonrelativistic spin-1/2 Dirac fermions from double exchange of spin-0 and spin-1 bosons proportional to couplings of the form $g_P^4$, $g_S^2{g}_P^2$, and $g_V^2{g}_A^2$. Our results for $g_P^4$ are in agreement with previous calculations that have appeared in the literature. We demonstrate the usefulness of this analysis to constrain spin-dependent couplings by presenting the results of a reanalysis of data from a short-range gravity experiment to derive an improved constraint on $(g_P^N{)}^2$, the pseudoscalar coupling for nucleons, in the range between $40$ and $200\mu$m of about a factor of 5 compared to previous limits. The spin-independent contribution from 2-boson exchange with axial-vector couplings requires special treatment and will be explored in another paper.

   hep-phgr-qchep-exPRD(2017)·20 citations
7. 07*

   Gravitational waves at aLIGO and vacuum stability with a scalar singlet extension of the Standard Model

   Csaba Balazs🇦🇺 · Andrew Fowlie🇦🇺 · Anupam Mazumdar🇬🇧 · Graham White🇦🇺

   A new gauge singlet scalar field can undergo a strongly first-order phase transition (PT) leading to gravitational waves (GW) potentially observable at aLIGO and simultaneously stabilize the electroweak vacuum. aLIGO (O5) is potentially sensitive to cosmological PTs at $10^7$-$10^8$ GeV, which coincides with the requirement that the singlet scale is less than the Standard Model (SM) vacuum instability scale, which is between $10^8$ GeV and $10^{14}$ GeV. After sampling its parameter space, we identify three benchmark points with a PT at about $T\approx 10^7$ GeV in a gauge singlet extension of the SM. We calculate the nucleation temperature, order parameter, characteristic timescale, and peak amplitude and frequency of GW from bubble collisions during the PT for the benchmarks and find that, in an optimistic scenario, GW from such a PT may be in reach of aLIGO (O5). We confirm that the singlet stabilizes the electroweak vacuum whilst remaining consistent with zero-temperature phenomenology as well. Thus, this scenario presents an intriguing possibility that aLIGO may detect traces of fundamental physics motivated by vacuum stability at an energy scale that is well above the reach of any other experiment.

   hep-phPRD(2017)·61 citations
8. 08*

   The exclusive Drell-Yan process and deeply virtual pion production

   Peter Kroll🇩🇪

   In this talk it is reported on analyses of l p -> l pi+ n and pi- p -> l+ l- n within the handbag approach. It is argued that recent measurements of hard pion production performed by HERMES and CLAS clearly indicate the occurrence of strong contributions from transversely polarized photons. The gamma*T -> pi transitions are described by the transversity GPDs accompanied by twist-3 pion wave functions. The experiments also require strong contributions from the pion pole which can be modeled as a classical one-pion exchange. With these extensions the handbag approach leads to results on cross sections and spin asymmetries in fair agreement with experiment. This approach is also used for an estimate of the partial cross sections for the exclusive Drell-Yan process.

   hep-phJPS Conf.Proc.(2017)·6 citations
9. 09*

   ${\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau }$ decay in scalar and vector leptoquark scenarios

   Xin-Qiang Li🇨🇳 · Ya-Dong Yang🇨🇳 · Xin Zhang🇨🇳

   It has been shown that the anomalies observed in $\bar{B}\to D^{(\ast )}\tau {\bar{\nu }}_{\tau }$ and $\bar{B}\to \bar{K}{\ell }^{+}{\ell }^{-}$ decays can be resolved by adding a single scalar or vector leptoquark to the Standard Model, while constraints from other precision measurements in the flavour sector can be satisfied without fine-tuning. To further explore these two interesting scenarios, in this paper, we study their effects in the semi-leptonic ${\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau }$ decay. Using the best-fit solutions for the operator coefficients allowed by the current data of mesonic decays, we find that (i) the two scenarios give similar amounts of enhancements to the branching fraction $\mathcal{B}({\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau })$ and the ratio $R_{{\Lambda }_c}=\mathcal{B}({\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau })/\mathcal{B}({\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell })$, (ii) the two best-fit solutions in each of these two scenarios are also indistinguishable from each other, (iii) both scenarios give nearly the same predictions as those of the Standard Model for the longitudinal polarizations of ${\Lambda }_c$ and $\tau$ as well as the lepton-side forward-backward asymmetry. With future measurements of these observables in ${\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau }$ decay at the LHCb, the two leptoquark scenarios could be further tested, and even differentiated from the other NP explanations for the $R_{D^{(\ast )}}$ anomalies. We also discuss the feasibility for the measurements of these observables at the LHC and the future $e^{+}{e}^{-}$ colliders.

   hep-phhep-exJHEP(2017)·75 citations
10. 10*

    Perturbative QCD and beyond: azimuthal angle correlations in deuteron-deuteron scattering from Bose-Einstein correlations

    E. Gotsman (Tel Aviv U.)🇮🇱 · E. Levin (Tel Aviv U./UTFSM)🇨🇱

    In this paper, we found within the framework of perturbative QCD, that in deuteron-deuteron scattering the Bose-Einstein correlations due to two parton showers production, induce azimuthal angle correlations, with three correlation lengths: the size of the deuteron ($R_D$), the proton radius ($R_N$), and the size of the BFKL Pomeron which, is closely related to the saturation momentum ($R_c\sim 1/Q_s$). These correlations are independent of the values of rapidities of the produced gluons (long range rapidity correlations), for large rapidities ($\text{bas}|y_1-y_2|\ge 1$), and have no symmetry with respect to $\varphi \to \pi -\varphi$ (${\vec{p}}_{T1}\to -{\vec{p}}_{T1}$). Therefore, they give rise to $v_n$ for all values of $n$, not only even values. The contributions with the correlation length $R_D$ and $R_N$ crucially depend on the non-perturbative contributions, and to obtain estimates of their values, requiries a lot of modeling, while the correlations with $R_c\sim 1/Q_s$ have a perturbative QCD origin, and can be estimated in the ColorGlass Condensate (CGC) approach.

    hep-phPRD(2017)·14 citations
11. 11*

    WW + jet at 14 and 100 TeV

    John Campbell🇺🇸 · David Miller🇬🇧 · Tania Robens🇩🇪

    In the current LHC run, an accurate understanding of Standard Model processes is extremely important. Processes including electroweak gauge bosons serve as standard candles for SM measurements, and equally constitute important backgrounds for Beyond-the-Standard Model (BSM) searches. We present here the next-to-leading order (NLO) QCD virtual contributions to W+W- + jet in an analytic format obtained through unitarity methods. We present results for the full process using the Monte Carlo event generator MCFM, and discuss total as well as differential cross-sections for the LHC with 14 TeV center-of-mass energy, as well as a future 100 TeV proton-proton machine.

    hep-phPoS(2016)·2 citations
12. 12*

    MSSM fits to the ATLAS 1 lepton excess

    Kamila Kowalska🇩🇪 · Enrico Maria Sessolo🇵🇱

    We use the framework of the p19MSSM to perform a fit to the mild excesses over the Standard Model background recently observed in three bins of the ATLAS 1-lepton + (b-)jets + MET search. We find a few types of spectra that can fit the emerging signal and at the same time are not excluded by other LHC searches. They can be grouped roughly in two categories. The first class is characterized by the presence of one stop or stop and sbottoms with mass in the ballpark of 700-800 GeV and a neutralino LSP of mass around 400 GeV, with or without the additional presence of an intermediate chargino. In the second type of scenarios the stop, lightest chargino, sbottom if present, and the neutralino are about or heavier than ~650 GeV and the signal originates from cascade decays of squarks of the 1st and 2nd generation, which should have a mass of 1.1-1.2 TeV. For the best-fit scenarios, we compare the global chi-squared with respect to several ATLAS and CMS searches with the corresponding chi-squared of the Standard Model expectation, showing that the putative signal is also favored globally with respect to the background only hypothesis. We point out that if the observed excess persists in the next round of data, it should be accompanied by associated significant excesses in all-hadronic final state searches.

    hep-phEPJC(2017)·1 citation
13. 13*

    Constraining in-medium heavy-quark energy-loss mechanisms via angular correlations between heavy and light mesons

    Martin Rohrmoser🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Thierry Gousset🇫🇷 · Jörg Aichelin🇫🇷

    Two-particle correlations obtained from parton showers that pass the hot and dense medium of the quark gluon plasma (QGP) can be used as an alternative observable, in addition to the combination of the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$, to study the mechanisms of in-medium heavy quark energy-loss. In particular, angular correlations represent a promising tool to distinguish between energy loss due to collisional and radiative interactions of jet and medium particles. To this end, parton cascades were created in Monte-Carlo simulations, where individual particles can undergo both parton splitting as well as an effective jet-medium interaction. A first model simulates the effects of induced radiations on parton cascades. Its consequences on angular correlations of partons within jets were studied in detail, with particular focus on angular broadening. The results can be compared to a second model that effectively describes elastic scatterings of jet and medium particles.

    hep-phJ.Phys.Conf.Ser.(2017)·7 citations
14. 14*

    Raymond and instantons: some recollections and the use of ADHM

    Chris P. Korthals Altes🇳🇱

    After the discovery of the BRST identities in 1974 Raymond spent some two years mostly on instantons. In those years we had a small group at the Centre Physique Théorique in Marseille discussing the physics and mathematics of instantons. The upshot of our discussions can be found in a set of lectures given by Raymond in Erice in 1977 and a year later in a Physics Reports volume. I present some recollections of that period; mostly how we were influenced by the twistor approach. I discuss the Atiyah-Drinfeld-Hitchin-Manin (ADHM) method to obtain instantons ("calorons") in thermal QCD following earlier work. The building blocks are a prepotential and a gauge invariant propagator. Then I will give surprisingly simple results in terms of these building blocks for the one loop vacuum response to a change in caloron parameters and some physical consequences for the effective action, in particular screening properties.

    hep-phphysics.hist-phNPB(2016)·0 citations
15. 15*

    Helicity coherence in binary neutron star mergers and non-linear feedback

    Amélie Chatelain🇫🇷 · Cristina Volpe🇫🇷

    Neutrino flavor conversion studies based on astrophysical environments usually implement neutrino mixings, neutrino interactions with matter and neutrino self-interactions. In anisotropic media, the most general mean-field treatment includes neutrino mass contributions as well, that introduce a coupling between neutrinos and antineutrinos termed helicity or spin coherence. We discuss resonance conditions for helicity coherence for Dirac and Majorana neutrinos. We explore the role of these mean-field contributions on flavor evolution in the context of a binary neutron star merger remnant. We find that resonance conditions can be satisfied in neutron star merger scenarios while adiabaticity is not sufficient for efficient flavor conversion. We analyse our numerical findings by discussing general conditions to have multiple MSW-like resonances, in presence of non-linear feedback, in astrophysical environments.

    hep-phPRD(2017)·30 citations
16. 16*

    Signals for Lorentz and CPT Violation in Atomic Spectroscopy Experiments and Other Systems

    Arnaldo J. Vargas🇺🇸

    The prospects of studying nonminimal operators for Lorentz violation using spectroscopy experiments with light atoms and muon spin-precession experiments are presented. Possible improvements on bounds on minimal and nonminimal operators for Lorentz violation are discussed.

    hep-phphysics.atom-ph0 citations
17. 17*

    Resummations in PDF fits

    Marco Bonvini🇬🇧

    In this contribution I discuss recent and ongoing progress on the inclusion of resummation effects in the fit of parton distributions.

    hep-phhep-exPoS(2016)·1 citation
18. 18*

    Antiprotons from dark matter annihilation through light mediators and a possible excess in AMS-02 $\bar{p}/p$ data

    Xian-Jun Huang🇨🇳 · Chun-Cheng Wei🇨🇳 · Yue-Liang Wu🇨🇳 · Wei-Hong Zhang🇨🇳 · Yu-Feng Zhou🇨🇳

    We show that in the scenario where dark matter (DM) particles annihilate through light mediators, the energy spectra of the final state cosmic-ray particles depend strongly on the mediator mass. For final state antiprotons, a spectrum with relatively narrow peak occurs when the mediator mass is comparable to the $\text{pbar}p$ production threshold. Of interest, the latest AMS-02 data on the $\text{pbar}/p$ flux ratio hint at a bump-like excess over the expected background in the energy range $\sim 100-450$ GeV. We show that such a light mediator scenario is favoured by the latest AMS-02 data over the scenarios of DM direct annihilation into the standard model particles and that of antiprotons produced from inside supernova remnants (SNRs), and is consistent with the upper limits derived from the Fermi-LAT data on the gamma rays towards the dwarf spheroidal galaxies. The $\text{pbar}/p$ flux ratio with energy above 450 GeV is predicted to fall with energy quickly, which can be easily distinguished from the other two scenarios as they predict the ratio to be flattening or rising up to multi-TeV region.

    hep-phPRD(2017)·40 citations
19. 19*

    Unintegrated double parton distributions

    K. Golec-Biernat🇵🇱 · A.M. Stasto🇺🇸

    We present the construction of unintegrated double parton distribution functions which include dependence on transverse momenta of partons. We extend the formulation which was used to obtain the single unintegrated parton distributions from the standard, integrated parton distribution functions. Starting from the homogeneous part of the evolution equations for the integrated double parton distributions, we construct the unintegrated double parton distributions as the convolutions of the integrated double distributions and the splitting functions, multiplied by the Sudakov form factors. We show that there exist three domains of external hard scales which require three distinct forms of the unintegrated double distributions. The additional transverse momentum dependence which arises through the Sudakov form factors leads to non-trivial correlations in the parton momenta. We also discuss the non-homogeneous contribution to the unintegrated double parton distributions, which arises due to the splitting of a single parton into daughter partons with high transverse momenta. We analyze two cases, the unfolding of the transverse momenta dependence from the last step of the evolution of two partons, and the case where the transverse momenta are generated directly from the single parton splitting.

    hep-phPRD(2017)·14 citations
20. 20*

    Unifying left-right symmetry and 331 electroweak theories

    Mario Reig🇪🇸 · José W.F. Valle🇪🇸 · C.A. Vaquera-Araujo🇪🇸

    We propose a realistic theory based on the $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{SU}(3{)}_{\mathrm{R}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ gauge group which requires the number of families to match the number of colors. In the simplest realization neutrino masses arise from the canonical seesaw mechanism and their smallness correlates with the observed V-A nature of the weak force. Depending on the symmetry breaking path to the Standard Model one recovers either a left-right symmetric theory or one based on the $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1)$ symmetry as the "next" step towards new physics.

    hep-phPLB(2017)·29 citations
21. 21*

    Electroweak baryogenesis and gravitational waves from a real scalar singlet

    Ville Vaskonen🇪🇪

    We consider a real scalar singlet field which provides a strong first-order electroweak phase transition via its coupling to the Higgs boson, and gives a $CP$ violating contribution on the top quark mass via a dimension-6 operator. We study the correlation between the baryon-to-entropy ratio produced by electroweak baryogenesis, and the gravitational wave signal from the electroweak phase transition. We show that future gravitational wave experiments can test, in particular, the region of the model parameter space where the observed baryon-to-entropy ratio can be obtained even if the new physics scale, which is explicit in the dimension-6 operator, is high.

    hep-phastro-ph.COPRD(2017)·243 citations
22. 22*

    Improved estimates of the pion-photon transition form factor in the $(1\le {\mathbf{Q}}^2\le 5)$~GeV${}^2$ range and their theoretical uncertainties

    S. V. Mikhailov🇷🇺 · A. V. Pimikov🇨🇳 · N. G. Stefanis🇩🇪

    We consider the pion-photon transition form factor at low to intermediate spacelike momenta within the theoretical framework of light-cone sum rules. We derive predictions which take into account all currently known contributions stemming from QCD perturbation theory up to the next-to-next-to-leading order (NNLO) and by including all twist terms up to order six. In order to enable a more detailed comparison with forthcoming high-precision data, we also estimate the main systematic theoretical uncertainties, stemming from various sources, and discuss their influence on the calculations --- in particular the dominant one related to the still uncalculated part of the NNLO contribution. The analysis addresses, in broad terms, also the role of the twist-two pion distribution amplitude derived with different approaches.

    hep-phEPJ Web Conf.(2017)·3 citations
23. 23*

    Extending two Higgs doublet models for two-loop neutrino mass generation and one-loop neutrinoless double beta decay

    Zhen Liu🇨🇳 · Pei-Hong Gu🇨🇳

    We extend some two Higgs doublet models, where the Yukawa couplings for the charged fermion mass generation only involve one Higgs doublet, by two singlet scalars respectively carrying a singly electric charge and a doubly electric charge. The doublet and singlet scalars together can mediate a two-loop diagram to generate a tiny Majorana mass matrix of the standard model neutrinos. Remarkably, the structure of the neutrino mass matrix is fully determined by the symmetric Yukawa couplings of the doubly charged scalar to the right-handed leptons. Meanwhile, a one-loop induced neutrinoless double beta decay can arrive at a testable level even if the electron neutrino has an extremely small Majorana mass. We also study other experimental constraints and implications including some rare processes and Higgs phenomenology.

    hep-phNPB(2017)·28 citations
24. 24*

    Schwinger mechanism in linear covariant gauges

    A. C. Aguilar🇧🇷 · D. Binosi🇮🇹 · J. Papavassiliou🇪🇸

    In this work we explore the applicability of a special gluon mass generating mechanism in the context of the linear covariant gauges. In particular, the implementation of the Schwinger mechanism in pure Yang-Mills theories hinges crucially on the inclusion of massless bound-state excitations in the fundamental nonperturbative vertices of the theory. The dynamical formation of such excitations is controlled by a homogeneous linear Bethe-Salpeter equation, whose nontrivial solutions have been studied only in the Landau gauge. Here, the form of this integral equation is derived for general values of the gauge-fixing parameter, under a number of simplifying assumptions that reduce the degree of technical complexity. The kernel of this equation consists of fully-dressed gluon propagators, for which recent lattice data are used as input, and of three-gluon vertices dressed by a single form factor, which is modelled by means of certain physically motivated Ansätze. The gauge-dependent terms contributing to this kernel impose considerable restrictions on the infrared behavior of the vertex form factor; specifically, only infrared finite Ansätze are compatible with the existence of nontrivial solutions. When such Ansätze are employed, the numerical study of the integral equation reveals a continuity in the type of solutions as one varies the gauge-fixing parameter, indicating a smooth departure from the Landau gauge. Instead, the logarithmically divergent form factor displaying the characteristic "zero crossing", while perfectly consistent in the Landau gauge, has to undergo a dramatic qualitative transformation away from it, in order to yield acceptable solutions. The possible implications of these results are briefly discussed.

    hep-phhep-lathep-thPRD(2017)·47 citations
25. 25*

    Mixed Inert Scalar Triplet Dark Matter, Radiative Neutrino Masses and Leptogenesis

    Wen-Bin Lu🇨🇳 · Pei-Hong Gu🇨🇳

    The neutral component of an inert scalar multiplet with hypercharge can provide a stable dark matter particle when its real and imaginary parts have a splitting mass spectrum. Otherwise, a tree-level dark matter-nucleon scattering mediated by the $Z$ boson will be much above the experimental limit. In this paper we focus on a mixed inert scalar triplet dark matter scenario where a complex scalar triplet with hypercharge can mix with another real scalar triplet without hypercharge through their renormalizable coupling to the standard model Higgs doublet. We consider three specified cases that carry most of the relevant features of the full parameter space: (i) the neutral component of the real triplet dominates the dark matter particle, (ii) the neutral component of the complex triplet dominates the dark matter particle; and (iii) the neutral components of the real and complex triplets equally constitute the dark matter particle. Subject to the dark matter relic abundance and direct detection constraint, we perform a systematic study on the allowed parameter space with particular emphasis on the interplay among triplet-doublet terms and gauge interactions. In the presence of these mixed inert scalar triplets, some heavy Dirac fermions composed of inert fermion doublets can be utilized to generate a tiny Majorana neutrino mass term at one-loop level and realize a successful leptogenesis for explaining the cosmic baryon asymmetry.

    hep-phNPB(2017)·41 citations
26. 26*

    Signatures of Flux Tube Fragmentation and Strangeness Correlations in pp Collisions

    Cheuk-Yin Wong🇺🇸

    In the fragmentation of a color flux tube in high-energy $pp$ collisions or $e^{+}$-$e^{-}$ annihilations, the production of $q$-$\bar{q}$ pairs along a color flux tube precedes the fragmentation of the tube. The local conservation laws in the production of these $q$-$\bar{q}$ pairs will lead to the correlations of adjacently produced hadrons. As a consequence, the fragmentation of a flux tube will yield a many-hadron correlation in the form of a chain of hadrons ordered in rapidity, with adjacent hadrons correlated in charges, flavor contents, and azimuthal angles. It will also lead to a two-hadron angular correlation between two hadrons with opposite charges or strangeness that is suppressed at $\Delta \varphi \sim 0$ but enhanced at $\Delta \varphi \sim \pi$, within a rapidity window $\Delta y$$\sim$$1/(dN/dy)$.

    hep-phJ.Phys.Conf.Ser.(2017)·0 citations
27. 27*

    Solar neutrinos, helicity effects and new affine gravity with torsion II

    David Alvarez-Castillo🇷🇺 · Diego Julio Cirilo-Lombardo🇦🇷 · Jilberto Zamora-Saa🇷🇺

    The cross section for neutrino helicity spin-flip obtained from a new f(R, T) model of gravitation with dynamic torsion field introduced by one of the authors in [1], is phenomenologically analyzed. To this end, due to the logarithmical energy dependence of the cross section, the relation with the axion decay constant fa (Peccei-Quinn parameter) is used. Consequently the link with the phenomenological energy/mass window is found from the astrophysical and high energy viewpoints. The highest helicity spin-flip cross-sectional values presented in this work coincide with a recent estimation on the axion mass computed in [2] in the framework of finite temperature extended lattice QCD and under cosmological considerations.

    hep-phgr-qchep-thJHEAp(2017)·9 citations
28. 28*

    The fourth dimension of the nucleon structure: spacetime analysis of the timelike electromagnetic proton form factors

    Andrea Bianconi🇮🇹 · Egle Tomasi-Gustafsson🇫🇷

    As well known, spacelike proton form factors expressed in the Breit frame may be interpreted as the Fourier transform of static space distributions of electric charge and current. In particular, the electric form factor is simply the Fourier transform of the charge distribution $F(q)=\int e^{i\vec{q}\cdot \vec{r}}\rho (r)d^{3}r$. We don't have an intuitive interpretation of the same level of simplicity for the proton timelike form factor appearing in the reactions $e^{+}{e}^{-}\leftrightarrow \bar{p}p$. However, one may suggest that in the center of mass (CM) frame, where $q_{\mu }{x}^{\mu }=qt$, a timelike electric form factor is the Fourier transform $F(q)=\int e^{iqt}R(t)dt$ of a function $R(t)$ expressing how the electric properties of the forming (or annihilating) proton-antiproton pair evolve in time. Here we analyze in depth this idea, show that the functions $\rho (r)$ and $R(t)$ can be formally written as the time and space integrals of a unique correlation function depending on both time and space coordinates.

    hep-phnucl-thPRC(2017)·9 citations
29. 29*

    CEPC Precision of Electroweak Oblique Parameters and Weakly Interacting Dark Matter: the Fermionic Case

    Chengfeng Cai🇨🇳 · Zhao-Huan Yu🇦🇺 · Hong-Hao Zhang🇨🇳

    Future electroweak precision measurements in the Circular Electron Positron Collider (CEPC) project would significantly improve the precision of electroweak oblique parameters. We evaluate the expected precision through global fits, and study the corresponding sensitivity to weakly interacting fermionic dark matter. Three models with electroweak multiplets in the dark sector are investigated as illuminating examples. We find that the CEPC data can probe up to TeV scales and explore some regions where direct detection cannot reach, especially when the models respect the custodial symmetry.

    hep-phhep-exNPB(2017)·43 citations
30. 30*

    Di-J/psi production at the Tevatron and the LHC

    Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇨🇭

    We briefly review recent results which we have obtained in the study of J/psi-pair production at the Tevatron and the LHC. We claim that the existing data set from CMS and D0 point at a significant double-parton-scattering contribution with an effective cross section smaller than that for jet-related observables. We have also derived simple relations involving feed-down fractions from excited states which can help in disentangling the single from the double scatterings.

    hep-phhep-exPoS(2016)·3 citations
31. 31*

    Jets and high-$p_T$ probes measured in the STAR experiment

    Nihar Ranjan Sahoo (for the STAR collaboration)🇺🇸

    Hard probes created through large momentum transfers are used to study the properties of QCD matter created in heavy-ion collisions, by comparing the measurements to those in p+p collisions. Jets, and the "quenching" or suppression of jets in the medium created in heavy-ion collisions, are studied through various different observables. We present the most recent measurements from $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions, with p+p collisions as the reference, by the STAR Collaboration. The observables are semi-inclusive charged jets and di-jet transverse momentum imbalance. Additionally, correlation measurements of direct photon-hadron and neutral pion-hadron are presented and discussed.

    ↳ nucl-exhep-exhep-phnucl-thPoS(2016)·0 citations
32. 32*

    A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton

    A. Gewering-Peine🇩🇪 · D. Horns🇩🇪 · J.H.M.M. Schmitt

    The Standard Model of particle physics can be extended to include sterile (right-handed) neutrinos or axions to solve the dark matter problem. Depending upon the mixing angle between active and sterile neutrinos, the latter have the possibility to decay into monoenergetic active neutrinos and photons in the keV-range while axions can couple to two photons. We have used data taken with X-ray telescopes like e.g. XMM-Newton for the search of line emissions. We used pointings with high exposures and expected dark matter column densities with respect to the dark matter halo of the Milky Way. The posterior predictive p-value analysis has been applied to locate parameter space regions which favour additional emission lines. In addition, upper limits of the parameter space of the models have been generated such that the preexisting limits have been significantly improved.

    ↳ astro-ph.HEhep-phJCAP(2017)·19 citations
33. 33*

    Inverted dipole feature in directional detection of exothermic dark matter

    Nassim Bozorgnia🇳🇱 · Graciela B. Gelmini🇺🇸 · Paolo Gondolo🇺🇸

    Directional dark matter detection attempts to measure the direction of motion of nuclei recoiling after having interacted with dark matter particles in the halo of our Galaxy. Due to Earth's motion with respect to the Galaxy, the dark matter flux is concentrated around a preferential direction. An anisotropy in the recoil direction rate is expected as an unmistakable signature of dark matter. The average nuclear recoil direction is expected to coincide with the average direction of dark matter particles arriving to Earth. Here we point out that for a particular type of dark matter, inelastic exothermic dark matter, the mean recoil direction as well as a secondary feature, a ring of maximum recoil rate around the mean recoil direction, could instead be opposite to the average dark matter arrival direction. Thus, the detection of an average nuclear recoil direction opposite to the usually expected direction would constitute a spectacular experimental confirmation of this type of dark matter.

    ↳ astro-ph.COhep-phJCAP(2017)·6 citations
34. 34*

    The Compton-Schwarzschild relations in higher dimensions

    Matthew J. Lake🇹🇭 · Bernard Carr🇬🇧

    In three spatial dimensions, the Compton wavelength $(R_C\propto M^{-1}$) and Schwarzschild radius $(R_S\propto M$) are dual under the transformation $M\to M_P^2/M$, where $M_P$ is the Planck mass. This suggests that there is a fundamental link -- termed the Black Hole Uncertainty Principle or Compton-Schwarzschild correspondence -- between elementary particles in the $M<M_P$ regime and black holes in the $M>M_P$ regime. In the presence of $n$ extra dimensions, compactified on some scale $R_E$, one expects $R_S\propto M^{1/(1+n)}$ for $R<R_E$, which breaks this duality. However, it may be restored in some circumstances because the effective Compton wavelength depends on the form of the $(3+n)$-dimensional wavefunction. If this is spherically symmetric, then one still has $R_C\propto M^{-1}$, as in the $3$-dimensional case. The effective Planck length is then increased and the Planck mass reduced, allowing the possibility of TeV quantum gravity and black hole production at the LHC. However, if the wave function is pancaked in the extra dimensions and maximally asymmetric, then $R_C\propto M^{-1/(1+n)}$, so that the duality between $R_C$ and $R_S$ is preserved. In this case, the effective Planck length is reduced but the Planck mass is unchanged, so TeV quantum gravity is precluded and black holes cannot be generated in collider experiments. Nevertheless, the extra dimensions could still have consequences for the detectability of black hole evaporations and the enhancement of pair-production at accelerators on scales below $R_E$. Though phenomenologically general for higher-dimensional theories, our results are shown to be consistent with string theory via the minimum positional uncertainty derived from $D$-particle scattering amplitudes.

    ↳ gr-qchep-phquant-ph15 citations
35. 35*

    Unique probe of dark matter in the core of M87 with the Event Horizon Telescope

    Thomas Lacroix🇫🇷 · Mansour Karami🇨🇦 · Avery E. Broderick🇨🇦 · Joseph Silk🇫🇷 · Celine Boehm🇬🇧

    We demonstrate the unprecedented capabilities of the Event Horizon Telescope (EHT) to image the innermost dark matter profile in the vicinity of the supermassive black hole at the center of the M87 radio galaxy. We present the first model of the synchrotron emission induced by dark matter annihilations from a spiky profile in the close vicinity of a supermassive black hole, accounting for strong gravitational lensing effects. Our results show that the EHT should readily resolve dark matter spikes if present. Moreover, the photon ring surrounding the silhouette of the black hole is clearly visible in the spike emission, which introduces observable small-scale structure into the signal. We find that the dark matter-induced emission provides an adequate fit to the existing EHT data, implying that in addition to the jet, a dark matter spike may account for a sizable portion of the millimeter emission from the innermost (subparsec) region of M87. Regardless, our results show that the EHT can probe very weakly annihilating dark matter. Current EHT observations already constrain very small cross sections, typically down to a few 10^{-31} cm^{3} s^{-1} for a 10 GeV candidate, close to characteristic values for p-wave-suppressed annihilation. Future EHT observations will further improve constraints on the DM scenario.

    ↳ astro-ph.GAastro-ph.COastro-ph.HEhep-phPRD(2017)·49 citations
36. 36*

    $B_c$ decays from highly improved staggered quarks and NRQCD

    Brian Colquhoun🇯🇵 · Christine Davies🇬🇧 · Jonna Koponen🇬🇧 · Andrew Lytle🇬🇧 · Craig McNeile (HPQCD collaboration)🇬🇧

    We calculate semileptonic form factors for the decays $B_c\to {\eta }_{c}l\nu$ and $B_c\to J/\psi l\nu$ over the entire $q^2$ range, using a highly improved lattice quark action for charm at several lattice spacings down to $a=0.045$ fm. We have two ways of treating the $b$ quark: either with an $O({\alpha }_s)$ improved NRQCD formalism or by extrapolating a heavy mass $m_h$ to $m_b$ in the relativistic formalism. Comparison of the two approaches provides an important cross-check of methodologies in lattice QCD. Nonperturbative renormalisation of the currents in the relativistic theory also allows us then to fix NRQCD-charm normalisation for $b$ to $c$ decays such as $B\to D$ and $B\to D^{\ast }$.

    ↳ hep-lathep-phPoS(2016)·56 citations
37. 37*

    Nonstandard cosmologies from physics beyond the Standard model

    M.Yu.Khlopov🇷🇺

    The modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy.It implies extension of particle symmetry beyond the Standard model. Studies of physical basis of the modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play important role. The cosmological consequences of particle models inevitably go beyond the 'standard' cosmological $\Lambda$CDM model and some possible feature of such 'nonstandard'cosmological scenarios is the subject of the present brief review.

    ↳ astro-ph.COhep-phBled Workshops Phys.(2016)·2 citations
38. 38*

    Singularity-free model of electrically charged fermionic particles and gauged Q-balls

    Vladimir Dzhunushaliev🇰🇿 · Arislan Makhmudov🇰🇿 · Konstantin G. Zloshchastiev🇿🇦

    We propose a model of an electrically charged fermion as a regular localized solution of electromagnetic and spinor fields interacting with a physical vacuum, which is phenomenologically described as a logarithmic superfluid. We analytically study the asymptotic behavior of the solution, while obtaining its form by numerical methods. The solution has physically plausible properties, such as finite size, self-energy, total charge and mass. In the case of spherical symmetry, its electric field obeys the Coulomb asymptotics at large distances from its core. It is shown that the observable rest mass of the fermion arises as a result of interaction of the fields with the physical vacuum. The spinor and scalar field components of the solution decay exponentially outside the core; therefore they can be regarded as internal degrees of freedom which can only be probed at sufficiently large scales of energy and momentum. Apart from conventional Fermi particles, our model can find applications in a theory of exotic localized objects, such as U(1) gauged Q-balls with half-integer spin.

    ↳ hep-thcond-mat.otherhep-phnlin.PSPRD(2016)·18 citations
39. 39*

    Compact Vortices

    D. Bazeia🇧🇷 · L. Losano🇧🇷 · M.A. Marques🇧🇷 · R. Menezes🇧🇷 · I. Zafalan🇧🇷

    We study a family of Maxwell-Higgs models, described by the inclusion of a function of the scalar field that represent generalized magnetic permeability. We search for vortex configurations which obey first-order differential equations that solve the equations of motion. We first deal with the asymptotic behavior of the field configurations, and then implement a numerical study of the solutions, the energy density and the magnetic field. We work with the generalized permeability having distinct profiles, giving rise to new models, and we investigate how the vortices behave, compared with the solutions of the corresponding standard models. In particular, we show how to build compact vortices, that is, vortex solutions with the energy density and magnetic field vanishing outside a compact region of the plane.

    ↳ hep-thcond-mat.supr-conhep-phEPJC(2017)·21 citations
40. 40*

    Next-to-soft corrections to high energy scattering in QCD and gravity

    A. Luna🇬🇧 · S. Melville🇬🇧 · S. G. Naculich🇺🇸 · C. D. White🇬🇧

    We examine the Regge (high energy) limit of 4-point scattering in both QCD and gravity, using recently developed techniques to systematically compute all corrections up to next-to-leading power in the exchanged momentum i.e. beyond the eikonal approximation. We consider the situation of two scalar particles of arbitrary mass, thus generalising previous calculations in the literature. In QCD, our calculation describes power-suppressed corrections to the Reggeisation of the gluon. In gravity, we confirm a previous conjecture that next-to-soft corrections correspond to two independent deflection angles for the incoming particles. Our calculations in QCD and gravity are consistent with the well-known double copy relating amplitudes in the two theories.

    ↳ hep-thgr-qchep-phJHEP(2017)·107 citations
41. 41*

    Lattice calculation of the pion transition form factor ${\pi }^0\to {\gamma }^{\ast }{\gamma }^{\ast }$

    Antoine Gérardin🇩🇪 · Harvey B. Meyer🇩🇪 · Andreas Nyffeler🇩🇪

    We calculate the pion transition form factor ${\mathcal{F}}_{{\pi }^0{\gamma }^{\ast }{\gamma }^{\ast }}(q_1^2,q_2^2)$, which describe the interaction of an on-shell pion with two off-shell photons, using lattice QCD simulations with two degenerate flavors of dynamical quarks. This form factor is the main ingredient in the calculation of the pion-pole contribution to hadronic light-by-light scattering in the muon $g-2$, $a_{\mu }^{\mathrm{HLbL};{\pi }^0}$. We focus our study on the spacelike region with photon virtualities up to $1.5{\mathrm{GeV}}^2$, not yet measured experimentally. Several lattice spacings and pion masses are used to extrapolate the results to the physical point and a comparison with different phenomenological models is performed. Finally, we use our extrapolated form factor to provide a lattice determinaiton of $a_{\mu }^{\mathrm{HLbL};{\pi }^0}$.

    ↳ hep-lathep-phPoS(2016)·4 citations
42. 42*

    Interacting fermions in rotation: chiral symmetry restoration, moment of inertia and thermodynamics

    M. N. Chernodub🇫🇷 · Shinya Gongyo🇯🇵

    We study rotating fermionic matter at finite temperature in the framework of the Nambu-Jona-Lasinio model. In order to respect causality the rigidly rotating system must be bound by a cylindrical boundary with appropriate boundary conditions that confine the fermions inside the cylinder. We show the finite geometry with the MIT boundary conditions affects strongly the phase structure of the model leading to three distinct regions characterized by explicitly broken (gapped), partially restored (nearly gapless) and spontaneously broken (gapped) phases at, respectively, small, moderate and large radius of the cylinder. The presence of the boundary leads to specific steplike irregularities of the chiral condensate as functions of coupling constant, temperature and angular frequency. These steplike features have the same nature as the Shubnikov-de Haas oscillations with the crucial difference that they occur in the absence of both external magnetic field and Fermi surface. At finite temperature the rotation leads to restoration of spontaneously broken chiral symmetry while the vacuum at zero temperature is insensitive to rotation ("cold vacuum cannot rotate"). As the temperature increases the critical angular frequency decreases and the transition becomes softer. A phase diagram in angular frequency-temperature plane is presented. We also show that at fixed temperature the fermion matter in the chirally restored (gapless) phase has a higher moment of inertia compared to the one in the chirally broken (gapped) phase.

    ↳ hep-thcond-mat.othercond-mat.quant-gashep-phJHEP(2017)·161 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.