Tue·Oct 20, 2015Tuesday·October 20, 2015

1. 01*

   Analytical Expressions for the Hard-Scattering Production of Massive Partons

   Cheuk-Yin Wong🇺🇸

   We obtain explicit expressions for the two-particle differential cross section and the two-particle angular correlation function in the hard-scattering production of massive partons in order to exhibit the ``ridge" structure on the away side in the hard-scattering process. The single-particle production cross section is also obtained and compared with the ALICE experimental data for charm production in pp collisions at 7 TeV at LHC.

   hep-phJ.Phys.Conf.Ser.(2016)·1 citation
2. 02*

   Dark Matter Decay to a Photon and a Neutrino: the Double Monochromatic Smoking Gun Scenario

   Chaïmae El Aisati🇧🇪 · Michael Gustafsson🇩🇪 · Thomas Hambye🇧🇪 · Tiziana Scarna🇧🇪

   In the energy range from few TeV to 25 TeV, upper bounds on the dark matter decay rate into high energy monochromatic neutrinos have recently become comparable to those on monochromatic gamma-ray lines. This implies clear possibilities of a future double "smoking-gun" evidence for the dark matter particle, from the observation of both a gamma and a neutrino line at the same energy. In particular, we show that a scenario where both lines are induced from the same dark matter particle decay leads to correlations that can already be tested. We study this "double monochromatic" scenario by considering the complete list of lowest dimensional effective operators that could induce such a decay. Furthermore, we argue that, on top of lines from decays into two-body final states, three-body final states can also be highly relevant. In addition to producing a distinct hard photon spectrum, three-body final states also produce a line-like feature in the neutrino spectrum that can be searched for by neutrino telescopes.

   hep-phastro-ph.HEPRD(2016)·29 citations
3. 03*

   Lattice tests of beyond Standard Model dynamics

   Thomas DeGrand🇺🇸

   Over the last few years lattice techniques have been used to investigate candidate theories of new physics beyond the Standard Model. This review gives a survey of results from these studies. Most of these investigations have been of systems of gauge fields and fermions that have slowly-running coupling constants. A major portion of the review is a critical discussion of work in this particular subfield, first describing the methods used, and then giving a compilation of results for specific models.

   hep-phhep-latRMP(2016)·136 citations
4. 04*

   Probing the Dark Sector with Dark Matter Bound States

   Haipeng An🇺🇸 · Bertrand Echenard🇺🇸 · Maxim Pospelov🇨🇦 · Yue Zhang🇺🇸

   A model of dark sector where $O(\mathrm{few}\mathrm{GeV})$ mass dark matter particles $\chi$ couple to a lighter dark force mediator $V$, $m_V\ll m_{\chi }$, is motivated by the recently discovered mismatch between simulated and observed shapes of galactic haloes. Such models, in general, provide a challenge for direct detection efforts and collider searches. We show that for a large range of coupling constants and masses, the production and decay of the bound states of $\chi$, such as $0^{-+}$ and $1^{--}$ states, ${\eta }_D$ and ${{\rm Y}}_D$, is an important search channel. We show that $e^{+}{e}^{-}\to {\eta }_D+V$ or ${{\rm Y}}_D+\gamma$ production at $B$-factories for ${\alpha }_D>0.1$ is sufficiently strong to result in multiple pairs of charged leptons and pions via ${\eta }_D\to 2V\to 2(l^{+}{l}^{-})$ and ${{\rm Y}}_D\to 3V\to 3(l^{+}{l}^{-})$ $(l=e,\mu ,\pi )$. The absence of such final states in the existing searches performed at \babar\ and Belle sets new constraints on the parameter space of the model. We also show that a search for multiple bremsstrahlung of dark force mediators, $e^{+}{e}^{-}\to \chi \bar{\chi }+nV$, resulting in missing energy and multiple leptons, will further improve the sensitivity to self-interacting dark matter.

   hep-phastro-ph.COhep-exPRL(2016)·46 citations
5. 05*

   The $\rho {\gamma }^{\ast }\to \pi (\rho )$ transition form factors in the Perturbative QCD factorization approach

   Ya-Lan Zhang🇨🇳 · Shan Cheng🇩🇪 · Jun Hua🇨🇳 · Zhen-Jun Xiao🇨🇳

   In this paper, we studied the $\rho {\gamma }^{\ast }\to \pi$ and $\rho {\gamma }^{\ast }\to \rho$ transition processes and made the calculations for the $\rho \pi$ transition form factor $Q^4{F}_{\rho \pi }(Q^2)$ and the $\rho$ meson electromagnetic form factors, $F_{\mathrm{LL},\mathrm{LT},\mathrm{TT}}(Q^2)$ and $F_{1,2,3}(Q^2)$, by employing the perturbative QCD (PQCD) factorization approach. For the $\rho {\gamma }^{\ast }\to \pi$ transition, we found that the contribution to form factor $Q^4{F}_{\rho \pi }(Q)$ from the term proportional to the distribution amplitude combination ${\varphi }_{\rho }^T(x_1){\varphi }_{\pi }^P(x_2)$ is absolutely dominant, and the PQCD predictions for both the size and the $Q^2$-dependence of this form factor $Q^4{F}_{\rho \pi }(Q^2)$ agree well with those from the extended ADS/QCD models or the light-cone QCD sum rule. For the $\rho {\gamma }^{\ast }\to \rho$ transition and in the region of $Q^2\ge 3$ GeV${}^2$, further more, we found that the PQCD predictions for the magnitude and their $Q^2$-dependence of the $F_1(Q^2)$ and $F_2(Q^2)$ form factors agree well with those from the QCD sum rule, while the PQCD prediction for $F_3(Q^2)$ is much larger than the one from the QCD sum rule.

   hep-phhep-exPRD(2015)·13 citations
6. 06*

   Models for SIMP dark matter and dark photon

   Hyun Min Lee🇰🇷 · Min-Seok Seo🇰🇷

   We give a review on the SIMP paradigm and discuss a consistent model for SIMP dark mesons in the context of a dark QCD with flavor symmetry. The $Z^{\prime }$-portal interaction is introduced being compatible with stable dark mesons and is responsible for making the SIMP dark mesons remain in kinetic equilibrium with the SM during the freeze-out process. The SIMP parameter space of the $Z^{\prime }$ gauge boson can be probed by future collider and direct detection experiments.

   hep-phastro-ph.COAIP Conf.Proc.(2016)·10 citations
7. 07*

   $a_0(980)$ as a companion pole of $a_0(1450)$

   Thomas Wolkanowski🇩🇪 · Francesco Giacosa🇩🇪

   Light scalar hadrons are often understood as dynamically generated resonances. These arise as `companion poles' in the propagators of $q\bar{q}$ seed states when accounting for meson-loop contributions to the self-energies of the latter. Following this idea, we demonstrate that for the scalar--isovector state $a_0(1450)$ the full one-loop propagator has two poles: a pole of the seed state $a_0(1450)$ and a companion pole corresponding to $a_0(980)$. The positions of these poles are studied by varying the relative coupling strength between the non-derivative and derivative parts of the interactions.

   hep-phPoS(2016)·2 citations
8. 08*

   BSM Lessons from the SM Higgs

   Andrea Wulzer🇮🇹

   In this talk I will review the implications on Standard Model (SM) and Beyond the SM (BSM) theory of the experimental exploration of the scalar sector. Given that the Higgs discovery has been the most important achievement, I will start with a general overview of its dramatic impact on the physics of fundamental interaction. Next, I will describe how scalar sector results, including the measurements of the Higgs couplings and mass and the negative searches for extra scalars, constrain concrete BSM scenarios related with Naturalness. In particular, I will discuss composite Higgs and low energy supersymmetry, both in its minimal and next-to-minimal implementations.

   hep-phPoS(2015)·5 citations
9. 09*

   Reheating-era leptogenesis

   Yuta Hamada🇯🇵 · Kiyoharu Kawana🇯🇵

   We propose a novel leptogenesis scenario at the reheating era. Our setup is minimal in the sense that, in addition to the standard model Lagrangian, we only consider an inflaton and higher dimensional operators. The lepton number asymmetry is produced not by the decay of a heavy particle, but by the scattering between the standard model particles. After the decay of an inflaton, the model is described within the standard model with higher dimensional operators. The Sakharov's three conditions are satisfied by the following way. The violation of the lepton number is realized by the dimension-5 operator. The complex phase comes from the dimension-6 four lepton operator. The universe is out of equilibrium before the reheating is completed. It is found that the successful baryogenesis is realized for the wide range of parameters, the inflaton mass and reheating temperature, depending on the cutoff scale. Since we only rely on the effective Lagrangian, our scenario can be applicable to all mechanisms to generate neutrino Majorana masses.

   hep-phastro-ph.COhep-thPLB(2016)·23 citations
10. 10*

    Composite Inflation in the light of 2015 Planck data

    Phongpichit Channuie (Walailak U.)🇹🇭

    In this work, we examine cosmological constraints on models of composite inflation based on the slow-roll approximation by using the recent Planck measurement. We compare the spectral index of curvature perturbation (and its running) and the tensor-to-scalar ratio predicted by such models with Planck 2015 data. We find that the predictions of technicolor inflation are nicely consistent with the Planck analysis. Moreover, the predictions from the second model, glueball inflation, are in good agreement with the Planck data at $2\sigma$C.L. However, the final two models, super glueball inflation and orientifold inflation, favor only the rather large value of the tensor-to-scalar ratio of which the predictions are in tension with the Planck analysis.

    hep-phastro-ph.COgr-qchep-thClass.Quant.Grav.(2016)·4 citations
11. 11*

    QCD sum rule calculation for P-wave bottom baryons

    Qiang Mao🇨🇳 · Hua-Xing Chen🇨🇳 · Wei Chen🇨🇦 · Atsushi Hosaka🇯🇵 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    We study the P-wave bottom baryons using the method of QCD sum rule and heavy quark effective theory. Our results suggest that Lambda_b(5912) and Lambda_b(5920) can be well described by the baryon doublet [3F_bar, 1, 1, rho], and they belong to the SU(3) 3F_bar multiplets of J(P)=1/2(-) and 3/2(-). Their SU(3) flavor partners, Xi_b(1/2-) and Xi_b(3/2-), have masses 6.06 \pm 0.13 GeV and 6.07 \pm 0.13 GeV, respectively, with mass splitting 9 \pm 4 MeV. The results obtained using baryon doublet [3F_bar, 1, 0, lambda] are similar and also consistent with the experimental data. We also study the SU(3) 6F multiplets by using the baryon multiplets [6F, 0, 1, lambda], [6_F, 1, 0, rho] and [6F, 2, 1, lambda], and our results suggest that the P-wave bottom baryons Sigma_b, Xi'_b and Omega_b have (averaged) masses about 6.0 GeV, 6.2 GeV and 6.4 GeV, respectively.

    hep-phPRD(2015)·95 citations
12. 12*

    Next-To-Leading Order Differential Cross-Sections for $J/\psi$, $\psi (2S)$ and ${\rm Y}$ Production in Proton-Proton Collisions at a Fixed-Target Experiment using the LHC Beams (AFTER@LHC)

    Y.Feng🇨🇳 · J.-X. Wang🇨🇳

    Using nonrelativistic QCD (NRQCD) factorization, we calculate the yields for $J/\psi$, $\psi (2S)$ and ${\rm Y}(1S)$ hadroproduction at $\sqrt{s}=$ 72 GeV and 115 GeV including the next-to-leading order QCD corrections. Both these center-of-mass energies correspond to those obtained with 7~TeV and 2.76~TeV nucleon beam impinging a fixed target. We study the cross section integrated in $p_t$ as a function of the rapidity as well as the $p_t$ differential cross section in the central rapidity region. Using different NLO fit results of the NRQCD long-distance matrix elements, we evaluate a theoretical uncertainty which is certainly much larger than the projected experimental uncertainties with the expected 20 fb${}^{-1}$ to be collected per year with AFTER@LHC.

    hep-phAdv.High Energy Phys.(2015)·5 citations
13. 13*

    Quark and Lepton Mass Matrix Model with Only Six Family-Independent Parameters

    Yoshio Koide🇯🇵 · Hiroyuki Nishiura🇯🇵

    We propose a unified mass matrix model for quarks and leptons, in which sixteen observables of mass ratios and mixings of the quarks and neutrinos are described by using no family number-dependent parameters except for the charged lepton masses and only six family number-independent free parameters. The model is constructed by extending the so-called "Yukawaon" model to a seesaw type model with the smallest number of possible family number-independent free parameters. As a result, once the six parameters is fixed by the quark mixing and the mass ratios of quarks and neutrinos, no free parameters are left in the lepton mixing matrix. The results are in excellent agreement with the neutrino mixing data. We predict ${\delta }_{CP}^{\ell }=-68^{\circ }$ for the leptonic $CP$ violating phase and $⟨m⟩\simeq 21$ meV for the effective Majorana neutrino mass.

    hep-phPRD(2015)·9 citations
14. 14*

    Prospects for Higgs- and Z-resonant Neutralino Dark Matter

    Koichi Hamaguchi🇯🇵 · Kazuya Ishikawa🇯🇵

    In the minimal supersymmetric standard models, neutralino dark matter with mass of $m_{\chi }\sim m_Z/2\sim 45$ GeV and $m_{\chi }\sim m_h/2\sim 62$ GeV can have the thermal relic abundance ${\Omega }_{{\chi }_1}{h}^2\simeq 0.120$ via the $Z$- and Higgs-resonant annihilations, respectively, while avoiding all the current constraints. Phenomenology of such scenarios is determined only by three parameters, Bino mass $M_1$, Higgsino mass $\mu$, and $\tan \beta$, in the limit that all other supersymmetric particles and heavy Higgs bosons are decoupled. In this paper, we comprehensively study the constraints and future prospects of the search for such Higgs- and $Z$-resonant neutralino dark matter. It is shown that almost all the parameter space of the scenario will be probed complementarily by the LHC search for the chargino and neutralinos, the direct detection experiments, and the Higgs invisible decay search at the ILC.

    hep-phhep-exPRD(2016)·39 citations
15. 15*

    On the smallness of the cosmological constant in SUGRA models with Planck scale SUSY breaking and degenerate vacua

    C. Froggatt🇬🇧 · R. Nevzorov🇦🇺 · H. B. Nielsen🇩🇰 · A. Thomas🇦🇺

    We argue that the exact degeneracy of vacua in N=1 supergravity can shed light on the smallness of the cosmological constant. The presence of such vacua, which are degenerate to very high accuracy, may also result in small values of the quartic Higgs coupling and its beta function at the Planck scale in the phase in which we live.

    hep-phastro-ph.COgr-qchep-thPoS(2015)·10 citations
16. 16*

    LHC signatures and cosmological implications of the E6 inspired SUSY models

    R. Nevzorov🇦🇺

    The phenomenological implications of the E6 inspired supersymmetric models based on the Standard Model gauge group together with extra U(1)_N gauge symmetry under which right-handed neutrinos have zero charge are examined. In these models single discrete symmetry forbids the tree-level flavour changing processes and the most dangerous operators that violate baryon and lepton numbers. The two-loop renormalisation group flow of the gauge and Yukawa couplings is explored and the qualitative pattern of the Higgs spectrum in the case of the quasi-fixed point scenario is discussed. These E6 inspired models contain two dark-matter candidates. The presence of exotic states in these models gives rise to the nonstandard decays of the lightest Higgs boson which are also considered.

    hep-phPoS(2015)·13 citations
17. 17*

    Collins functions for pions from SIDIS and new e+e- data: a first glance at their transverse momentum dependence

    M. Anselmino🇮🇹 · M. Boglione🇮🇹 · U. D'Alesio🇮🇹 · J.O. Gonzalez Hernandez🇮🇹 · S. Melis🇮🇹 · F. Murgia🇮🇹 · A. Prokudin🇺🇸

    New data from Belle and BaBar Collaborations on azimuthal asymmetries, measured in e+e- annihilations into pion pairs at Q^2=112 GeV^2, allow to take the first, direct glance at the transverse momentum dependence of the Collins functions, in addition to their z dependence. These data, together with available Semi-Inclusive Deep Inelastic Scattering (SIDIS) data on the Collins asymmetry, are simultaneously analysed in the framework of the generalised parton model assuming two alternative Q^2 evolution schemes and exploiting two different parameterisations for the Collins functions. The corresponding results for the transversity distributions are presented. Analogous data, newly released by the BESIII Collaboration, on e+e- annihilations into pion pairs at the lower Q^2 of 13 GeV^2, offer the possibility to explore the sensitivity of these azimuthal correlations on transverse momentum dependent evolution effects.

    hep-phhep-exPRD(2015)·113 citations
18. 18*

    On the strong coupling $N^{(\ast )}{N}^{(\ast )}\pi$

    K. Azizi🇹🇷 · Y. Sarac🇹🇷 · H. Sundu🇹🇷

    We study the strong vertices $N^{\ast }N\pi$, $N^{\ast }{N}^{\ast }\pi$ and $NN\pi$ in QCD, where $N^{\ast }$ denotes the negative parity $N(1535)$ state. We use the most general form of the interpolating currents to calculate the corresponding strong coupling constants. It is obtained that the coupling associated to $N^{\ast }N\pi$ vertex is strongly suppressed compared to those related to two other vertices. The strong coupling corresponding to $N^{\ast }{N}^{\ast }\pi$ is obtained to be roughly half of that of $NN\pi$ vertex. We compare the obtained results on $N^{\ast }N\pi$ and $NN\pi$ vertices with the existing predictions of other theoretical studies as well as those extracted from the experimental data.

    hep-phEPJA(2016)·14 citations
19. 19*

    Schwinger mechanism revisited

    Francois Gelis🇫🇷 · Naoto Tanji🇩🇪

    In this article, we review recent theoretical works on the Schwingermechanism of particle production in external electrical fields. Although the non-perturbative Schwinger mechanism is at the center of this discussion, many of the approaches that we discuss can cope with general time and space dependent fields, and therefore also capture the perturbative contributions to particle production.

    hep-phhep-thnucl-thPPNP(2016)·194 citations
20. 20*

    The calorimetric spectrum of the electron-capture decay of ${}^{163}$Ho. A preliminary analysis of the preliminary data

    A. De Rújula🇪🇸 · M. Lusignoli🇮🇹

    It is in principle possible to measure directly the electron neutrino mass (or masses and mixing angles) in weak electron-capture decays. The optimal nuclide in this respect is ${}^{163}$Ho. The favoured experimental technique, currently pursued in various experiments (ECHo, HOLMES and NuMECS) is "calorimetric". The calorimetric energy spectrum is a sum over the unstable vacant orbitals, or "holes", left by the electrons weakly captured by the nucleus. We discuss the current progress in this field and analize the preliminary data. Our conclusion is that, as pointed out by Robertson, the contribution of two-hole states is not negligible. But --in strong contradistinction with the tacit conclusion of previous comparisons of theory and observations-- we find a quite satisfactory agreement. A crucial point is that, in the creation of secondary holes, electron shakeoff and not only electron shakeup must be taken into account.

    hep-phnucl-thphysics.atom-ph14 citations
21. 21*

    Approach to the time development of parton fragmentation

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

    It is the central goal of our studies to describe parton fragmentation in the hot and dense medium of a quark gluon plasma (QGP). Under the assumption that the medium is not static and homogeneous, knowledge about the temporal evolution of the processes involved can be of essential importance. Therefore, parton fragmentation has been studied with a Monte-Carlo algorithm that approximates the DGLAP-evolution of fragmentation functions via a set of parton cascades. The presented work consists mainly of implementations of this kind of algorithm and the application of a simple approximation, which gives the time development of partonic cascades. As approximations to the parton-splitting processes of gluons and massless quarks in the vacuum two different schemes with the same leading-log contributions are investigated. Furthermore, the temporal evolutions of quantities related to partonic cascades have been examined: To our understanding, especially variables (like, e.g.: parton multiplicities or virtualities) that give insight, when parton splittings take place, are of great interest, as they allow identifying the parts of the fragmentation process that will be most affected by medium interactions.

    hep-phPoS(2015)·0 citations
22. 22*

    The GENIE Neutrino Monte Carlo Generator: Physics and User Manual

    Costas Andreopoulos🇬🇧 · Christopher Barry🇬🇧 · Steve Dytman🇺🇸 · Hugh Gallagher🇺🇸 · Tomasz Golan🇺🇸 · Robert Hatcher🇺🇸 · Gabriel Perdue🇺🇸 · Julia Yarba🇺🇸

    GENIE is a suite of products for the experimental neutrino physics community. This suite includes i) a modern software framework for implementing neutrino event generators, a state-of-the-art comprehensive physics model and tools to support neutrino interaction simulation for realistic experimental setups (the Generator product), ii) extensive archives of neutrino, charged-lepton and hadron scattering data and software to produce a comprehensive set of data/MC comparisons (the Comparisons product), and iii) a generator tuning framework and fitting applications (the Tuning product). This book provides the definite guide for the GENIE Generator: It presents the software architecture and a detailed description of its physics model and official tunes. In addition, it provides a rich set of data/MC comparisons that characterise the physics performance of GENIE. Detailed step-by-step instructions on how to install and configure the Generator, run its applications and analyze its outputs are also included.

    hep-phhep-ex483 citations
23. 23*

    The pion-cloud contribution to the electromagnetic nucleon structure

    D. Kupelwieser🇦🇹 · W. Schweiger🇦🇹

    The present contribution continues and extends foregoing work on the calculation of electroweak form factors of hadrons using the point-form of relativistic quantum mechanics. Here we are particularly interested in studying pionic effects on the electromagnetic structure of the nucleon. To this aim we employ a hybrid constituent-quark model that comprises, in addition to the $3q$ valence component, also a $3q$+$\pi$ non-valence component. With a simple wave function for the $3q$ component we get reasonable results for the nucleon form factors. In accordance with other authors we find that the pionic effect is significant only below $Q^2\lesssim 0.5$~GeV${}^2$.

    hep-phnucl-thBled Workshops Phys.(2015)·0 citations
24. 24*

    The nature of massive neutrinos and multiple mechanisms in neutrinoless double beta decay

    Aurora Meroni🇩🇰

    Determining the nature -Dirac or Majorana- of massive neutrinos is one of the most pressing and challenging problems in the field of neutrino physics. We discuss how one can possibly extract information on the couplings, if any, which might be involved in neutrinoless double beta-decay using a multi-isotope approach. We investigate as well the potential of combining data on the half-lives of nuclides which largely different Nuclear Matrix Elements such as ${}^{136}$Xe and of one or more of the four nuclei ${}^{76}$Ge, ${}^{82}$Se, ${}^{100}$Mo and ${}^{130}$Te, for discriminating between different pairs of non-interfering or interfering mechanisms of neutrinoless double beta-decay. The case studies do not extend to the evaluation of the theoretical uncertainties of the results, due to the nuclear matrix elements calculations and other causes.

    hep-phEur.Phys.J.Plus(2015)·1 citation
25. 25*

    Derivative interactions and perturbative UV contributions in N Higgs Doublet Models

    Yohei Kikuta🇯🇵 · Yasuhiro Yamamoto🇪🇸

    We study the Higgs derivative interactions on models including arbitrary number of the Higgs doublets. These interactions are generated by two ways. One is higher order corrections of composite Higgs models, and the other is integrating out heavy scalars and vectors. In the latter case, three point couplings between the Higgs doublets and them are the sources of the derivative interactions. The representations of these heavy particles are constrained to couple with the doublets. We explicitly calculate the all derivative interactions generated by integrating out. Their degrees of freedom and conditions to impose the custodial symmetry are discussed. We also study the vector boson scattering processes with a couple of two Higgs doublet models to see experimental signals of the derivative interactions. They are differently affected by each heavy field.

    hep-phEPJC(2016)·6 citations
26. 26*

    Two, three, many body systems involving mesons. Multimeson condensates

    E. Oset🇪🇸 · M. Bayar🇹🇷 · A. Dote🇯🇵 · T. Hyodo🇯🇵 · P. K. Khemchandani🇧🇷 · W. H. Liang🇨🇳 · A. Martinez Torres🇧🇷 · M. Oka🇯🇵 · L.Roca🇪🇸 · T. Uchino🇪🇸 · C.W. Xiao🇩🇪

    In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.

    hep-phnucl-thActa Phys.Polon.B(2016)·3 citations
27. 27*

    Remarks on measurement of the decay ${\Xi }_b^{-}\to {\Lambda }_b{\pi }^{-}$

    M.B. Voloshin🇺🇸

    The interpretation of the recent observation by LHCb of a heavy-flavor-conserving and strangeness-changing decay ${\Xi }_b^{-}\to {\Lambda }_b{\pi }^{-}$ in terms of the branching fraction for the decay suffers from the uncertainty in the yield of the ${\Xi }_b^{-}$ hyperons relative to that of the ${\Lambda }_b$. It is pointed out here that this relative yield can be determined with a significantly reduced uncertainty by measuring within the same experimental conditions the decays related by the flavor $SU(3)$ symmetry and/or the heavy quark symmetry, such as ${\Xi }_b\to J/\psi \Xi$, ${\Lambda }_b\to J/\psi \Lambda$, or ${\Xi }_b^{-}\to {\Xi }_c^0\ell \nu$, ${\Lambda }_b\to {\Lambda }_c\ell \nu$.

    hep-phhep-ex17 citations
28. 28*

    A Mechanism of Ultraviolet Naturalness

    Durmus Ali Demir🇹🇷

    The Standard Model (SM), as the quantum field theory of the strong and electroweak interactions, needs be carried into curved spacetime to incorporate gravity. This is done here not for the full but for the effective SM action by integrating-in affine curvature. This approach leads to naturalization of the SM Higgs sector and reduction of the cosmological constant down to the neutrino scale thanks to the fact that quadratic (quartic) UV contributions to the Higgs boson mass (vacuum energy) turn into the Higgs-curvature coupling (the Einstein-Hilbert term). New physics beyond the SM, necessary for inducing gravity properly, does not have to interact with the SM. It can form a secluded sector to source non-interacting dark matter observable via only gravity, or a weakly-coupled sector to source dark matter and possible collider signals.

    hep-phgr-qchep-th13 citations
29. 29*

    Symmetries and unitary interactions of mass dimension one fermionic dark matter

    Cheng-Yang Lee🇧🇷

    The fermionic fields constructed from Elko have several unexpected properties. They satisfy the Klein-Gordon but not the Dirac equation and are of mass dimension one instead of three-half. Starting with the Klein-Gordon Lagrangian, we initiate a careful study of the symmetries and interactions of these fermions and their higher-spin generalisations. We find, although the fermions are of mass dimension one, the four-point fermionic self-interaction violates unitarity at high-energy. Therefore, it cannot be a fundamental interaction of the theory. It follows that for the spin-half fermions, the demand of renormalisability and unitarity forbids four-point interactions and only allows for the Yukawa interaction. For fermions with spin j>1/2, they have no renormalisable or unitary interactions. Since the theory is described by a Klein-Gordon Lagrangian, the interaction generated by the local $U(1)$ gauge symmetry which contains a four-point interaction, is excluded by the demand of renormalisability. In the context of the Standard Model, these properties make the spin-half fermions natural dark matter candidates.

    ↳ hep-thhep-phInt.J.Mod.Phys.A(2016)·15 citations
30. 30*

    Ultra high energy cosmic rays and possible signature of black strings

    Rita C. Anjos🇧🇷 · Carlos H. Coimbra-Araújo🇧🇷 · Roldao da Rocha🇧🇷 · Vitor de Souza🇧🇷

    Ultra high energy cosmic rays (UHECRs) probably originate in extreme conditions in which extra dimension effects might be important. In this paper we calculate the correction in black hole accretion mechanisms due to extra dimension effects in the static and rotating cases. A parametrization of the external Kerr horizons in both cases is presented and analysed. We use previous calculations of upper limits on the UHECR flux to set limits on the UHECR production efficiency of nine sources. The upper limit on the UHECR luminosity calculation is based on GeV-TeV gamma-ray measurements. The total luminosity due to the accretion mechanism is compared to the upper limit on UHECRs. The dependence of the UHECR production efficiency upper limit on black hole mass is also presented and discussed

    ↳ hep-thastro-ph.HEhep-phJCAP(2016)·8 citations
31. 31*

    Electromagnetic effects on the light hadron spectrum

    MILC Collaboration: S. Basak (1)🇮🇳 · A. Bazavov (2)🇺🇸 · C. Bernard (3)🇺🇸 · C. DeTar (4)🇺🇸 · E. Freeland (5)🇺🇸 · J. Foley (4)🇺🇸 · Steven Gottlieb (6)🇺🇸 · U. M. Heller (7)🇺🇸 · J. Komijani (3)🇺🇸 · J. Laiho (8)🇺🇸 · L. Levkova (4)🇺🇸 · R. Li (6)🇺🇸 and 6 other authors

    For some time, the MILC Collaboration has been studying electromagnetic effects on light mesons. These calculations use fully dynamical QCD, but only quenched photons, which suffices to NLO in XPT. That is, the sea quarks are electrically neutral, while the valence quarks carry charge. For the photons we use the non-compact formalism. We have new results with lattice spacing as small as 0.045 fm and a large range of volumes. We consider how well chiral perturbation theory describes these results and the implications for light quark masses

    ↳ hep-lathep-phJ.Phys.Conf.Ser.(2015)·23 citations
32. 32*

    Chiral phase transition and Schwinger mechanism in a pure electric field

    Gaoqing Cao🇨🇳 · Xu-Guang Huang🇨🇳

    We systematically study the chiral symmetry breaking and restoration in the presence of a pure electric field in the Nambu--Jona-Lasinio (NJL) model at finite temperature and baryon chemical potential. In addition, we also study the effect of the chiral phase transition on the charged pair production due to the Schwinger mechanism. For these purposes, a general formalism for parallel electric and magnetic fields is developed at finite temperature and chemical potential for the first time. In the pure electric field limit $B\to 0$, we compute the order parameter, the transverse-to-longitudinal ratio of the Goldstone mode velocities, and the Schwinger pair production rate as functions of the electric field. The inverse catalysis effect of the electric field to chiral symmetry breaking is recovered. And the Goldstone mode is find to disperse anisotropically such that the transverse velocity is always smaller than the longitudinal one, especially at nonzero temperature and baryon chemical potential. As expected, the quark-pair production rate is greatly enhanced by the chiral symmetry restoration.

    ↳ nucl-thhep-phhep-thPRD(2016)·30 citations
33. 33*

    Large N meson masses from a matrix model

    Antonio González-Arroyo🇪🇸 · Masanori Okawa🇯🇵

    We explain how to compute meson masses in the large $N$ limit using the twisted Eguchi-Kawai model. A very simple formula is derived, and we show how it leads in a fast and efficient way to results which are in fairly good agreement with other determinations. The method is easily extensible to reduced models with dynamical fermions based on the twisted reduction idea.

    ↳ hep-lathep-phhep-thPLB(2016)·28 citations
34. 34*

    Searches for Majorana Neutrinos and Direct Searches for Exotics at LHCb

    X. Cid Vidal (on behalf of the LHCb collaboration)🇨🇭

    These proceedings present the LHCb results on Majorana neutrino searches and direct production of exotic particles using the data collected during Run I of LHC. For the former, Majorana neutrinos are searched for both on-shell and off-shell in $B$ and $D$ decays to final states with two same-sign muons. For the latter, different types of new particles are studied profiting the unique coverage of LHCb with respect to other detectors.

    ↳ hep-exhep-ph2 citations
35. 35*

    No Vacuum Cerenkov Radiation Losses in the Timelike Lorentz-Violating Chern-Simons Theory

    Karl Schober🇺🇸 · Brett Altschul🇺🇸

    In a Lorentz- and CPT-violating modification of electrodynamics that includes a timelike Chern-Simons term, there are no energy losss through vacuum Cerenkov radiation. A charge moving with a constant velocity does not lose energy, because of an unusual cancellation. Higher frequency modes of the electromagnetic field carry away positive energy, but lower frequency modes carry away a compensating negative amount of energy.

    ↳ hep-thhep-phPRD(2015)·27 citations
36. 36*

    Quark deconfinement and the duration of short Gamma Ray Bursts

    Alessandro Drago (1) · Andrea Lavagno (2) · Brian Metzger (3) · Giuseppe Pagliara (1) ((1) Ferrara U. & INFN, Ferrara, (2) Turin Polytechnic & INFN, Turin, (3) Columbia U., Astron. Astrophys.)

    We propose a model for short duration gamma-ray bursts (sGRBs) based on the formation of a quark star after the merger of two neutron stars. We assume that the sGRB central engine is a proto-magnetar, which has been previously invoked to explain the plateau-like X-ray emission observed following both long and short GRBs. Here, we show that: i) a few milliseconds after the merger it is possible to form a stable and massive star made in part of quarks; ii) during the early cooling phase of the incompletely formed quark star, the flux of baryons ablated from the surface by neutrinos is large and it does not allow the outflow to achieve a bulk Lorentz factor high enough to produce a GRB; iii) after the quark burning front reaches the stellar surface, baryon ablation ceases and the jet becomes too baryon poor to produce a GRB; iv) however, between these two phases a GRB can be produced over the finite timescale required for the baryon pollution to cease; a characteristic timescale of the order of $\sim 0.1$ s naturally results from the time the conversion front needs to cover the distance between the rotational pole and the latitude of the last closed magnetic field line; v) we predict a correlation between the luminosity of the sGRB and its duration, consistent with the data; vi) our model also predicts a delay of the order of ten seconds between the time of the merger event and the sGRB, allowing for the possibility of precursor emission and implying that the jet will encounter the dense cocoon formed immediately after the merger.

    ↳ astro-ph.HEhep-phnucl-thPRD(2016)·34 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.