Thu·Feb 18, 2016Thursday·February 18, 2016

1. 01*

   Anomalous coupling, top-mass and parton-shower effects in $W^{+}{W}^{-}$ production

   Johannes Bellm🇬🇧 · Stefan Gieseke🇩🇪 · Nicolas Greiner🇨🇭 · Gudrun Heinrich🇩🇪 · Simon Platzer🇬🇧 · Christian Reuschle🇺🇸 · Johann Felix von Soden-Fraunhofen🇩🇪

   We calculate the process $pp\to W^{+}{W}^{-}\to e^{+}{\nu }_e{\mu }^{-}{\bar{\nu }}_{\mu }$ at NLO QCD, including also effective field theory (EFT) operators mediating the $gg{W}^{+}{W}^{-}$ interaction, which first occur at dimension eight. We further combine the NLO and EFT matrix elements produced by GoSam with the HERWIG7/MATCHBOX framework, which offers the possibility to study the impact of a parton shower. We assess the effects of the anomalous couplings by comparing them to top-mass effects as well as uncertainties related to variations of the renormalisation, factorisation and hard shower scales.

   hep-phJHEP(2016)·22 citations
2. 02*

   Indirect Detection Imprint of a CP Violating Dark Sector

   Wei Chao🇺🇸 · Michael J. Ramsey-Musolf🇺🇸 · Jiang-Hao Yu🇺🇸

   We introduce a simple scenario involving fermionic dark matter ($\chi$) and singlet scalar mediators that may account for the Galactic Center GeV $\gamma$-ray excess while satisfying present direct detection constraints. CP-violation in the scalar potential leads to mixing between the Standard Model Higgs boson and the scalar singlet, resulting in three scalars $h_{1,2,3}$ of indefinite CP-transformation properties. This mixing enables s-wave $\chi \bar{\chi }$ annihilation into di-scalar states, followed by decays into four fermion final states. The observed $\gamma$-ray spectrum can be fitted while respecting present direct detection bounds and Higgs boson properties for $m_{\chi }=60\sim 80$ GeV, and $m_{h_3}\sim m_{\chi }$. Searches for the Higgs exotic decay channel $h_1\to h_3{h}_3$ at the 14 TeV LHC should be able to further probe the parameter region favored by the $\gamma$-ray excess.

   hep-phPRD(2016)·11 citations
3. 03*

   Pushing Higgs Effective Theory over the Edge

   Anke Biekötter🇩🇪 · Johann Brehmer🇩🇪 · Tilman Plehn🇩🇪

   Based on a vector triplet model we study a possible failure of dimension-6 operators in describing LHC Higgs kinematics. First, we illustrate that including dimension-6 contributions squared can significantly improve the agreement between the full model and the dimension-6 approximation, both in associated Higgs production and in weak-boson-fusion Higgs production. Second, we test how a simplified model with an additional heavy scalar could improve the agreement in critical LHC observables. In weak boson fusion we find an improvement for virtuality-related observables at large energies, but at the cost of sizeable deviations in interference patterns and angular correlations.

   hep-phPRD(2016)·54 citations
4. 04*

   Coleman-Weinberg symmetry breaking in $SU(8)$ induced by a third rank antisymmetric tensor scalar field

   Stephen L. Adler🇺🇸

   We study $SU(8)$ symmetry breaking induced by minimizing the Coleman-Weinberg effective potential for a third rank antisymmetric tensor scalar field in the 56 representation. Instead of breaking $SU(8)\supset SU(3)\times SU(5)$, we find that the stable minimum of the potential breaks the original symmetry according to $SU(8)\supset SU(3)\times Sp(4)$. Using both numerical and analytical methods, we present results for the potential minimum, the corresponding Goldstone boson structure and BEH mechanism, and the group-theoretic classification of the residual states after symmetry breaking.

   hep-phhep-thJ.Phys.A(2016)·8 citations
5. 05*

   Diphoton decay for a 750 GeV scalar boson in a $SU(6)\otimes U(1{)}_X$ model

   S. F. Mantilla🇨🇴 · R. Martinez🇨🇴 · F. Ochoa🇨🇴 · C. F. Sierra🇨🇴

   We propose a new $SU(6)\otimes U(1{)}_X$ GUT model free from anomalies, with a 750 GeV scalar candidate which can decay into two photons, compatible with the recent diphoton signal reported by ATLAS and CMS collaborations. This model gives masses to all fermions and may explain the 750GeV signal through one loop decays to $\gamma \gamma$ with charged vector and charged Higgs bosons, as well as up- and electron-like exotic particles that arise naturally from the condition of cancellation of anomalies of the $SU(6)\otimes U(1{)}_X$ group. We obtain, for different width approximations, allowed mass regions from 900 GeV to 3 TeV for the exotic up-like quark, in agreement with ATLAS and CMS collaborations data.

   hep-phNPB(2016)·20 citations
6. 06*

   Critical Temperature of Chiral Symmetry Restoration for Quark Matter with a Chiral Chemical Potential

   M. Ruggieri🇨🇳 · G. X. Peng🇨🇳

   In this article we study restoration of chiral symmetry at finite temperature for quark matter with a chiral chemical potential, ${\mu }_5$, by means of a nonlocal Nambu-Jona-Lasinio model. This model allows to introduce in the simplest way possible a Euclidean momentum, $p_E$, dependent quark mass function which decays (neglecting logarithms) as $1/p_E^2$ for large $p_E$, in agreement with asymptotic behaviour expected in QCD in presence of a nonperturbative quark condensate. We focus on the critical temperature for chiral symmetry restoration in the chiral limit, $T_c$, versus ${\mu }_5$, as well as on the order of the phase transition. We find that $T_c$ increases with ${\mu }_5$, and that the transition remains of the second order for the whole range of ${\mu }_5$ considered.

   hep-phhep-latJ.Phys.G(2016)·47 citations
7. 07*

   A Model for Pseudo-Dirac Neutrinos: Leptogenesis and Ultra-High Energy Neutrinos

   Y. H. Ahn🇰🇷 · Sin Kyu Kang🇰🇷 · C. S. Kim🇰🇷

   We propose a model where sterile neutrinos are introduced to make light neutrinos to be pseudo-Dirac particles. It is shown how tiny mass splitting necessary for realizing pseudo-Dirac neutrinos can be achieved. Within the model, we show how leptogenesis can be successfully generated. Motivated by the recent observation of very high energy neutrino events at IceCube, we study a possibility to observe the effects of the pseudo-Dirac property of neutrinos by performing astronomical-scale baseline experiments to uncover the oscillation effects of very tiny mass splitting. Using the result of global fit to neutrino data for the input of neutrino mixing angles and CP phase at $1\sigma$ C.L. and fixing neutrino energy and mass splittings, we study how the oscillation effects induced by pseudo-Dirac neutrinos may affect the track-to-shower ratio obtained from IceCube data. We also discuss future prospect to observe the effects of the pseudo-Dirac property of neutrinos at high energy neutrino experiments.

   hep-phJHEP(2016)·28 citations
8. 08*

   Search for the $a_0(980)-f_0(980)$ mixing in weak decays of $D_s/B_s$ mesons

   Wei Wang🇨🇳

   Scalar mesons $a_0^0(980)$ and $f_0(980)$ can mix with each other through isospin violating effects, and the mixing intensity has been predicted at the percent level in various theoretical models. However the mixing has not been firmed established on the experimental side to date. In this work we explore the possibility to extract the $a_0-f_0$ mixing intensity using weak decays of heavy mesons: $D_s\to [{\pi }^0\eta ,\pi \pi ]e^{+}\nu$, $B_s\to [{\pi }^0\eta ,\pi \pi ]{\ell }^{+}{\ell }^{-}$ and the $B_s\to J/\psi [{\pi }^0\eta ,{\pi }^{+}{\pi }^{-}]$ decays. Based on the large amount of data accumulated by various experimental facilities including BEPC-II, LHC, Super KEKB and the future colliders, we find that the $a_0-f_0$ mixing intensity might be determined to a high precision, which will lead to a better understanding of the nature of scalar mesons.

   hep-phhep-exPLB(2016)·36 citations
9. 09*

   No $\nu$ floors: Effective field theory treatment of the neutrino background in direct dark matter detection experiments

   James B. Dent🇺🇸 · Bhaskar Dutta🇺🇸 · Jayden L. Newstead🇺🇸 · Louis E. Strigari🇺🇸

   Distinguishing a dark matter interaction from an astrophysical neutrino-induced interaction will be major challenge for future direct dark matter searches. In this paper, we consider this issue within non-relativistic Effective Field Theory (EFT), which provides a well-motivated theoretical framework for determining nuclear responses to dark matter scattering events. We analyze the nuclear energy recoil spectra from the different dark matter-nucleon EFT operators, and compare to the nuclear recoil energy spectra that is predicted to be induced by astrophysical neutrino sources. We determine that for 11 of the 14 possible operators, the dark matter-induced recoil spectra can be cleanly distinguished from the corresponding neutrino-induced recoil spectra with moderate size detector technologies that are now being pursued, e.g., these operators would require 0.5 tonne years to be distinguished from the neutrino background for low mass dark matter. Our results imply that in most models detectors with good energy resolution will be able to distinguish a dark matter signal from a neutrino signal, without the need for much larger detectors that must rely on additional information from timing or direction.

   hep-phastro-ph.COPRD(2016)·66 citations
10. 10*

    Hadron energy spectrum in polarized top quark decays considering the effects of hadron and bottom quark masses

    S. Mohammad Moosavi Nejad🇮🇷 · Mahboobe Balali🇮🇷

    We present the analytical expressions for the next-to-leading order corrections to the partial decay width $t(\uparrow )\to b{W}^{+}$, followed by $b\to H_{b}X$, for nonzero b-quark mass ($m_b\ne 0$) in the fixed-flavor-number scheme (FFNs). To make the predictions for the energy distribution of outgoing hadrons $H_b$, as a function of the normalized $H_b$-energy fraction $x_H$, we apply the general-mass variable-flavor-number scheme (GM-VFNs) in a specific helicity coordinate system where the polarization of top quark is evaluated relative to the b-quark momentum. We also study the effects of gluon fragmentation and finite hadron mass on the hadron energy spectrum so that hadron masses are responsible for the low-$x_H$ threshold. In order to describe both the b-quark and the gluon hadronizations in top decays we apply realistic and nonperturbative fragmentation functions extracted through a global fit to $e^{+}{e}^{-}$ annihilation data from CERN LEP1 and SLAC SLC by relying on their universality and scaling violations.

    hep-phEPJC(2016)·24 citations
11. 11*

    New observables for multiple-parton interactions measurements using Z + jets process at the LHC

    M. Bansal🇮🇳 · S. Bansal🇮🇳 · R. Kumar🇮🇳 · J. B. Singh🇮🇳

    Multiple-parton interactions play a vital role in hadron-hadron collisions. This paper presents a study of the multiple-parton interactions with simulated Z + jets events in proton-proton collisions at a centre-of-mass energy of 13 TeV. The events are simulated with POWHEG followed by hadronization and parton-showering using PYTHIA 8. The events with dimuon invariant mass in the range of 60--120 GeV are selected for the analysis. The charged particle jets, having minimum transverse momentum of 5 GeV and absolute pseudo-rapidity less than 2, are used to construct the observables for measurements of the multiple-parton interactions. The proposed observables and phase-space region presented in this paper found to have enhanced sensitivity to multiple-parton interactions. The increased sensitivity to MPI will be lead to precise constraints on the parameters of the MPI models.

    hep-phPRD(2016)·11 citations
12. 12*

    Composite Accidental Axions

    Michele Redi🇮🇹 · Ryosuke Sato🇮🇱

    We present several models where the QCD axion arises accidentally. Confining gauge theories can generate axion candidates whose properties are uniquely determined by the quantum numbers of the new fermions under the Standard Model. The Peccei-Quinn symmetry can emerge accidentally if the gauge theory is chiral. We generalise previous constructions in a unified framework. In some cases these models can be understood as the deconstruction of 5-dimensional gauge theories where the Peccei-Quinn symmetry is protected by locality but more general constructions are possible.

    hep-phhep-thJHEP(2016)·105 citations
13. 13*

    Drell-Yan production of multi Z'-bosons at the LHC within Non-Universal ED and 4D Composite Higgs Models

    Elena Accomando🇬🇧 · Daniele Barducci🇫🇷 · Stefania De Curtis🇮🇹 · Juri Fiaschi🇬🇧 · Stefano Moretti🇬🇧 · Claire H. Shepherd-Themistocleous🇬🇧

    The Drell-Yan di-lepton production at hadron colliders is by far the preferred channel to search for new heavy spin-1 particles. Traditionally, such searches have exploited the Narrow Width Approximation (NWA) for the signal, thereby neglecting the effect of the interference between the additional Z'-bosons and the Standard Model Z and {\gamma}. Recently, it has been established that both finite width and interference effects can be dealt with in experimental searches while still retaining the model independent approach ensured by the NWA. This assessment has been made for the case of popular single Z'-boson models currently probed at the CERN Large Hadron Collider (LHC). In this paper, we test the scope of the CERN machine in relation to the above issues for some benchmark multi Z'-boson models. In particular, we consider Non-Universal Extra Dimensional (NUED) scenarios and the 4-Dimensional Composite Higgs Model (4DCHM), both predicting a multi-Z' peaking structure. We conclude that in a variety of cases, specifically those in which the leptonic decays modes of one or more of the heavy neutral gauge bosons are suppressed and/or significant interference effects exist between these or with the background, especially present when their decay widths are significant, traditional search approaches based on the assumption of rather narrow and isolated objects might require suitable modifications to extract the underlying dynamics.

    hep-phJHEP(2016)·21 citations
14. 14*

    Time to move on?

    John Ellis🇬🇧

    Cosmology and particle physics have long been dominated by theoretical paradigms: Einstein's general theory of relativity in cosmology and the Standard Model of particle physics. The time may have come for paradigm shifts. Does cosmological inflation require a modification of Einstein's gravity? Have experiments at the LHC discovered a new particle beyond the Standard Model? It is premature to answer these questions, but we theorists can dream about the possibilities.

    hep-phastro-ph.COgr-qchep-thInt.J.Mod.Phys.D(2016)·3 citations
15. 15*

    One-loop renormalisation of the NMSSM in SloopS : 1. the neutralino-chargino and sfermion sectors

    G. Belanger🇫🇷 · V. Bizouard🇫🇷 · F. Boudjema🇫🇷 · G. Chalons🇫🇷

    We have completed the one-loop renormalisation of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) allowing for and comparing between different renormalisation schemes. A special attention is paid to on-shell schemes. We study a variety of these schemes based on alternative choices of the physical input parameters. In this paper we present our approach to the renormalisation of the NMSSM and report on our results for the neutralino-chargino and sfermion sectors. We will borrow some results from our study of the Higgs sector whose full discussion is left for a separate publication. We have implemented the set up for all the sectors of the NMSSM within \sloops, a code for the automatic computation of one-loop corrections initially developed for the standard model and the MSSM. Among the many applications that allows the code, we present here the one-loop corrections to neutralino masses and to partial widths of neutralinos and charginos into final states with one gauge boson. One-loop electroweak and QCD corrections to the partial widths of third generation sfermions into a fermion and a chargino or a neutralino are also computed.

    hep-phPRD(2016)·22 citations
16. 16*

    Bilinear quark operator renormalization at generalized symmetric point

    J.M. Bell🇬🇧 · J.A. Gracey🇬🇧

    We compute Green's functions with a bilinear quark operator inserted at non-zero momentum for a generalized momentum configuration to two loops. These are required to assist lattice gauge theory measurements of the same quantity in matching to the high energy behaviour. The flavour non-singlet operators considered are the scalar, vector and tensor currents as well as the second moment of the twist-2 Wilson operator used in deep inelastic scattering for the measurement of nucleon structure functions.

    hep-phhep-latPRD(2016)·6 citations
17. 17*

    Neutrino Cross section Future

    Sowjanya Gollapinni🇺🇸

    The study of neutrino-nucleus interactions has recently received renewed attention due to their importance in interpreting the neutrino oscillation data. Over the past few years, there has been continuous disagreement between neutrino cross section data and predictions due to lack of accurate nuclear models suitable for modern experiments which use heavier nuclear targets. Also, the current short and long-baseline neutrino oscillation experiments focus in the few GeV region where several distinct neutrino processes come into play resulting in complex nuclear effects. Despite recent efforts, more experimental input is needed to improve nuclear models and reduce neutrino interaction systematics which are currently dominating oscillation searches together with neutrino flux uncertainties. A number of new detector concepts with diverse neutrino beams and nuclear targets are currently being developed to provide necessary inputs required for next generation oscillation experiments. This paper summarizes these efforts along with a discussion of future prospects for precision cross section measurements.

    ↳ hep-exhep-phphysics.ins-det7 citations
18. 18*

    Weak and strong coupling limits of the Boltzmann equation in the relaxation-time approximation

    Amaresh Jaiswal🇩🇪 · Bengt Friman🇩🇪 · Krzysztof Redlich🇵🇱

    We consider a momentum dependent relaxation time for the Boltzmann equation in the relaxation time approximation. We employ a power law parametrization for the momentum dependence of the relaxation time, and calculate the shear and bulk viscosity, as well as, the charge and heat conductivity. We show, that for the two popular parametrizations, referred to as the linear and quadratic ansatz, one can obtain transport coefficients which corresponds to the weak and strong coupling regimes, respectively. We also show that, for a system of massless particles with vanishing chemical potential, the off-equilibrium corrections to the phase-space distribution function calculated with the quadratic ansatz are identical with those of the Grad's 14-moment method.

    ↳ nucl-thhep-ph11 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.