Thu·Jan 14, 2016Thursday·January 14, 2016

1. 01*

   Warped $R-$Parity Violation

   B.C. Allanach🇬🇧 · A.M. Iyer🇮🇳 · K. Sridhar🇮🇳

   We consider a modified Randall-Sundrum (RS) framework between the Planck scale and the GUT scale. In this scenario, RS works as a theory of flavour and not as a solution to the hierarchy problem. The latter is resolved by supersymmetrising the bulk, so that the minimal supersymmetric standard model being the effective 4-dimensional theory. Matter fields are localised in the bulk in order to fit fermion-mass and mixing-data. If $R$-parity violating terms are allowed in the superpotential, their orders of magnitude throughout flavour space are then predicted, resulting in rich flavour textures. If the $R$-parity violating contributions to neutrino masses are somewhat suppressed, then lepton-number violating models exist which explain the neutrino oscillation data while not being in contradiction with current experimental bounds. Another promising model is one where baryon number is violated and Dirac neutrino masses result solely from fermion localisation. We sketch the likely discovery signatures of the baryon-number and the lepton-number violating cases.

   hep-phPRD(2016)·0 citations
2. 02*

   Chiral-odd GPDs in large-N_c QCD

   P. Schweitzer🇺🇸 · C. Weiss🇺🇸

   We study the flavor structure of the nucleon's chiral-odd generalized parton distributions (transversity GPDs) in the large-N_c limit of QCD. It is found that in the distributions H_T and E_T-tilde the flavor-nonsinglet component u - d is leading in the 1/N_c expansion, while in E_T and H_T-tilde it is the flavor-singlet component u + d. This pattern is consistent with the flavor structure extracted from hard exclusive pi^0 and eta electroproduction data, assuming that the processes are dominated by the twist-3 mechanism involving the chiral-odd pseudoscalar meson distribution amplitudes.

   hep-phPoS(2015)·4 citations
3. 03*

   Upper Limit on Forward Charm Contribution to Atmospheric Neutrino Flux

   Francis Halzen🇺🇸 · Logan Wille🇺🇸

   We revisit the calculation of charm particle production in hadron collisions, focusing on the production of charm particles that carry a large fraction of the momentum of the incident proton. In the case of strange particles, such a component is familiar from the abundant production of $K^{+}\Lambda$ pairs. Modern collider experiments have no coverage in the very large rapidity region where the forward pair production dominates. While forward charm particles are produced inside the LHC beampipe, they dominate the high-energy atmospheric neutrino flux in underground experiments because long-lived pions and kaons interact before decaying into neutrinos. The fragmentation of the spectator quark in the partonic subprocesses $qc\to qc$ and $gc\to gc$ is responsible for the forward component of charm production in perturbative QCD. We use this phenomenological framework to construct a charm cross section that saturates available accelerator and cosmic ray data, i.e., it represents an upper limit on the normalization of the charm cross section that cannot be reliably calculated because the charm mass is much smaller than the center-of-mass energy. Where the highest energy IceCube observations are concerned, we conclude that the upper limit on the flux of neutrinos from forward charm production may dominate the much-studied central component. It may therefore also represent a significant contribution to the TeV atmospheric neutrino flux but cannot accommodate the PeV flux of high-energy cosmic neutrinos observed by IceCube, or even the excess of events observed in the 30 TeV energy range.

   hep-phastro-ph.HE17 citations
4. 04*

   High-Scale Axions without Isocurvature from Inflationary Dynamics

   John Kearney🇺🇸 · Nicholas Orlofsky🇺🇸 · Aaron Pierce🇺🇸

   Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation $H_I$. If the scale of Peccei-Quinn (PQ) breaking $f_a$ is greater than $\frac{H_I}{2\pi }$, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation $f_I$ require either late-time dilution of the axion abundance or highly super-Planckian $f_I$ that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow $f_a$ close to the Planck scale. Avoiding disruption of inflationary dynamics provides important limits on the parameter space.

   hep-phastro-ph.COPRD(2016)·37 citations
5. 05*

   Direct photon production and jet energy-loss in small systems

   Chun Shen🇨🇦 · Chanwook Park🇨🇦 · Jean-François Paquet🇨🇦 · Gabriel S. Denicol🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   Two types of penetrating probes, direct photon and QCD jets, are investigated in the background of a small and rapidly expanding droplet of quark-gluon plasma. The additional thermal electromagnetic radiation results in a $\sim$50\% enhancement of the direct photons. In high multiplicity p+Pb collisions, jets can lose a sizeable fraction of their initial energy, leading to a charged hadron $R_{\mathrm{pA}}$ of $\sim$0.8 at a transverse momentum around 10\,GeV. Those two proposed measurements can help understand the apparent collective behaviour observed in small collision systems.

   hep-phnucl-exnucl-thNPA(2016)·16 citations
6. 06*

   Enhanced color gauge invariance and a new di-photon state at the LHC

   Stephon Alexander🇺🇸 · Lee Smolin🇨🇦

   We propose to interpret the possible resonance seen in di-photons at the LHC at 750 Gev as a bound state of a new pair of heavy gluons associated with an enhanced color gauge invariance. These have a conservation law which enforces their production and decay in pairs and hence requires that the leading coupling to quarks is quadratically through a dimension 5 operator. One way to realize these hypotheses is if the SU(3) color gauge invariance is enhanced to SL(3, C), while at the same time promoting the internal metric, which picks out what is a unitary transformation, to a dynamical degree of freedom. This theory was first proposed by Cahill[3], Dell[4], Kim and Zee[5], and Julia and Luciani[6]. The dynamical internal metric spontaneously breaks SL(3,C) to SU(3) giving a mass to the vector bosons associated with the generators in SL(3,C)/SU(3). The coupling to the internal metric also ensures that the energy is bounded from below. The new state is produced by gluon fusion and decays to a pair of photons via a direct coupling to a new set of vector quarks allowed by the symmetries.

   hep-ph15 citations
7. 07*

   Rapidity regulators in the semi-inclusive deep inelastic scattering and Drell-Yan processes

   Sean Fleming🇺🇸 · Ou Z. Labun🇺🇸

   We study the semi-inclusive limit of the deep inelastic scattering and Drell-Yan (DY) processes in soft collinear effective theory. In this regime so-called threshold logarithms must be resummed to render perturbation theory well behaved. Part of this resummation occurs via the Dokshitzer, Gribov, Lipatov, Altarelli, Parisi (DGLAP) equation, which at threshold contains a large logarithm that calls into question the convergence of the anomalous dimension. We demonstrate here that the problematic logarithm is related to rapidity divergences, and by introducing a rapidity regulator can be tamed. We show that resumming the rapidity logarithms allows us to reproduce the standard DGLAP running at threshold as long as a set of potentially large non-perturbative logarithms are absorbed into the definition of the parton distribution function (PDF). These terms could, in turn, explain the steep fall-off of the PDF in the endpoint. We then go on to show that the resummation of rapidity divergences does not change the standard threshold resummation in DY, nor do our results depend on the rapidity regulator we choose to use.

   hep-phnucl-thPRD(2017)·3 citations
8. 08*

   The Significance of the 750 GeV Fluctuation in the ATLAS Run 2 Diphoton Data

   Jonathan H. Davis🇬🇧 · Malcolm Fairbairn🇬🇧 · John Heal🇬🇧 · Patrick Tunney🇬🇧

   We investigate the robustness of the resonance like feature centred at around a 750 GeV invariant mass in the 13 TeV diphoton data, recently released by the ATLAS collaboration. We focus on the choice of empirical function used to model the continuum diphoton background in order to quantify the uncertainties in the analysis due to this choice. We extend the function chosen by the ATLAS collaboration to one with two components. By performing a profile likelihood analysis we find that the local significance of a resonance drops from $3.9\sigma$ using the ATLAS background function, and a freely-varying width, to only $2\sigma$ with our own function. We argue that the latter significance is more realistic, since the former was derived using a function which is fit almost entirely to the low-energy data, while underfitting in the region around the resonance.

   hep-ph38 citations
9. 09*

   Combined effect of NSI and SFP on solar electron neutrino oscillation

   Deniz Yilmaz🇹🇷

   The combined effect of SFP and the non standard neutrino interaction (NSI) on the survival probability of solar electron neutrinos (assumed to be Dirac particles) is examined for various values of ${ϵ}_{11}$, ${ϵ}_{12}$ and $\mu B$. It is found that the neutrino survival probability curves affected by SFP and NSI effects individually for some values of the parameters (${ϵ}_{11}$, ${ϵ}_{12}$ and $\mu B$) get close to the standard MSW curve when both effects are combined. Therefore, the combined effect of SFP and NSI needs to be taken into account when the solar electron neutrino data obtained by low energy solar neutrino experiments is investigated.

   hep-phAdv.High Energy Phys.(2016)·5 citations
10. 10*

    Wigner distributions and orbital angular momentum of a proton

    D. Chakrabarti🇮🇳 · T. Maji🇮🇳 · C. Mondal🇮🇳 · A. Mukherjee🇮🇳

    The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact parameter plane are presented for both u and d quarks.

    hep-phEPJC(2016)·51 citations
11. 11*

    Identifying the Universal part of TMDs

    F.F. Van der Veken🇧🇪 · N.G. Stefanis🇩🇪

    We attempt to identify a path layout in the definition of transverse-momentum-dependent T-odd parton distribution functions (TMD)s which combines features of both, initial- and final-state interactions, so that it remains universal despite the fact that the Wilson lines entering such TMDs change their orientation. The generic structure of the quark correlator for this path layout is calculated.

    hep-phFew Body Syst.(2016)·0 citations
12. 12*

    New results at LHC confirming the vacuum stability and Multiple Point Principle

    L.V. Laperashvili🇷🇺 · H.B. Nielsen🇩🇰 · C.R. Das🇷🇺

    In the present paper we argue that the correction to the Higgs mass coming from the bound state of 6 top and 6 anti-top quarks, predicted early by C.D. Froggatt and ourselves, leads to the Standard Model vacuum stability and confirms the accuracy of the multiple point principle (principle of degenerate vacua) for all experimentally valued parameters (Higgs mass, top-quark mass, etc.). Fitting to get the vacuum degeneracy requires a mass of the bound state, just in the region of the new two photon state in LHC, 750-760 GeV.

    hep-phInt.J.Mod.Phys.A(2016)·30 citations
13. 13*

    Hidden-charm molecular pentaquarks and their charm-strange partners

    Rui Chen🇨🇳 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

    In the framework of one-pion-exchange (OPE) model, we study the hidden-charm and charm-strange molecular pentaquark systems composed of a heavy baryon $({\Sigma }_c,{\Sigma }_c^{\ast })$ and a vector meson $({\bar{K}}^{\ast },{\bar{D}}^{\ast })$, where the S-D mixing effect is considered in our calculation. Our result shows that the ${\Sigma }_c{\bar{D}}^{\ast }$ molecular state with $(I=1/2,J^P=3/2^{-})$ and the ${\Sigma }_c^{\ast }{\bar{D}}^{\ast }$ molecular state with $(I=1/2,J^P=5/2^{-})$ exist in the mass range of the observed $P_c(4380)$ and $P_c(4450)$, respectively. Moreover, we predict two other hidden-charm molecular pentaquarks with configurations ${\Sigma }_c{\bar{D}}^{\ast }$ $(I=3/2,J^P=1/2^{-})$ and ${\Sigma }_c^{\ast }{\bar{D}}^{\ast }$ $(I=3/2,J^P=1/2^{-})$ and two charm-strange molecular pentaquarks $P_{cs}(3340)$ and $P_{cs}(3400)$ corresponding to the ${\Sigma }_c{\bar{K}}^{\ast }$ configuration with $(I=1/2,J^P=3/2^{-})$ and the ${\Sigma }_c^{\ast }{\bar{K}}^{\ast }$ configuration with $(I=1/2,J^P=5/2^{-})$, respectively. Additionally, we also predict some hidden-bottom ${\Sigma }_b^{(\ast )}{B}^{\ast }$ and $B_c$-like ${\Sigma }_c^{(\ast )}{B}^{\ast }/{\Sigma }_b^{(\ast )}{\bar{D}}^{\ast }$ pentaquarks.

    hep-phhep-exNPA(2016)·72 citations
14. 14*

    Is symmetry breaking of SU(5) theory responsible for the diphoton excess?

    Ilja Dorsner🇭🇷 · Svjetlana Fajfer🇸🇮 · Nejc Kosnik🇸🇮

    We advocate the possibility that the observed diphoton excess at 750 GeV at the LHC can be addressed by the scalar field that is a part of the SU(5) symmetry breaking sector. The field in question is the Standard Model singlet that resides in the adjoint representation that breaks SU(5) down to SU(3) x SU(2) x U(1). We also show that the required production and subsequent decay to two photons of this singlet can be induced by individual or combined contribution of two scalar multiplets $S_3$ and $R_2$ that transform as (3,3,-1/3) and (3,2,7/6) under SU(3) x SU(2) x U(1), respectively. The individual dominance of these multiplets is directly related to the issue of the charged fermion mass generation within the SU(5) framework and can be unambiguously tested through the diboson decay signatures of the Standard Model singlet field.

    hep-phPRD(2016)·41 citations
15. 15*

    Initial state of Heavy-Ion Collisions: Isotropization and thermalization

    Aleksi Kurkela🇨🇭

    I discuss how local thermal equilibrium and hydrodynamical flow are reached in heavy-ion collisions in the weak coupling limit.

    hep-phnucl-thNPA(2016)·40 citations
16. 16*

    The $\Delta (27)$ flavor 3-3-1 model with neutral leptons

    V. V. Vien🇻🇳 · A. E. Cárcamo Hernández🇨🇱 · H. N. Long🇻🇳

    We build the first 3-3-1 model based on the $\Delta (27)$ discrete group symmetry, consistent with fermion masses and mixings. In the model under consideration, the neutrino masses are generated from a combination of type-I and type-II seesaw mechanisms mediated by three heavy right-handed Majorana neutrinos and three $SU(3{)}_L$ scalar antisextets, respectively. Furthermore, from the consistency of the leptonic mixing angles with their experimental values, we obtain a non-vanishing leptonic Dirac CP violating phase of $-\frac{\pi }{2}$. Our model features an effective Majorana neutrino mass parameter of neutrinoless double beta decay, with values $m_{\beta \beta }=$ 10 and 18 meV for the normal and the inverted neutrino mass hierarchies, respectively.

    hep-phNPB(2016)·64 citations
17. 17*

    The pseudo chiral magnetic effect in QED3

    A. J. Mizher🇲🇽 · A. Raya🇲🇽 · C. Villavicencio🇨🇱

    Chiral magnetic effect (CME) has been suggested to take place during peripheral relativistic heavy ion collisions. However, signals of its realization are not yet independent of ambiguities and thus probing the non-trivial topological vacua of quantum chromodynamics (QCD) is still an open issue. Weyl materials, particularly graphene, on the other hand, are effectively described at low energies by the degrees of freedom of quantum electrodynamics in two spatial dimensions, QED3. This theory shares with QCD some interesting features, like confinement and chiral symmetry breaking and also possesses a non-trivial vacuum structure. In this regard, an analog of the CME is proposed to take place in graphene under the influence of an in-plane magnetic field in which the pseudo-spin or flavor label of charge carriers is participant of the effect, rather than the actual spin. In this contribution, we review the parallelisms and differences between the CME and the so-called pseudo chiral magnetic effect, PCME.

    hep-phNucl.Part.Phys.Proc.(2016)·4 citations
18. 18*

    Revisiting the $B^0\to {\pi }^0{\pi }^0$ decays in the perturbative QCD approach

    Yun-Feng Li🇨🇳 · Xian-Qiao Yu🇨🇳

    We recalculate the branching ratio and CP asymmetry for ${\bar{B}}^0(B^0)\to {\pi }^0{\pi }^0$ decays in the Perturbative QCD approach. In this approach, we consider all the possible diagrams including non-factorizable contributions and annihilation contributions. We obtain $Br({\bar{B}}^0(B^0)\to {\pi }^0{\pi }^0)=(1.17_{-0.12}^{+0.11})\times 10^{-6}$. Our result is in agreement with the latest measured branching ratio of $B^0\to {\pi }^0{\pi }^0$ by the Belle and HFAG Collaborations. We also predict large direct CP asymmetry and mixing CP asymmetry in $B^0\to {\pi }^0{\pi }^0$ decays, which can be tested by the coming Belle-II experiments.

    hep-phPRD(2017)·4 citations
19. 19*

    The hadronic vacuum polarization contribution to $a_{\mu }$ from full lattice QCD

    Bipasha Chakraborty🇬🇧 · C. T. H. Davies🇬🇧 · P. G. de Oliviera🇬🇧 · J. Koponen🇬🇧 · G. P. Lepage🇺🇸 · R. van de Water🇺🇸

    We determine the contribution to the anomalous magnetic moment of the muon from the ${\alpha }_{\mathrm{QED}}^2$ hadronic vacuum polarization diagram using full lattice QCD and including $u/d$ quarks with physical masses for the first time. We use gluon field configurations that include $u$, $d$, $s$ and $c$ quarks in the sea at multiple values of the lattice spacing, multiple $u/d$ masses and multiple volumes that allow us to include an analysis of finite-volume effects. We obtain a result for $a_{\mu }^{\mathrm{HVP},\mathrm{LO}}$ of $667(6)(12)$, where the first error is from the lattice calculation and the second includes systematic errors from missing QED and isospin-breaking effects and from quark-line disconnected diagrams. Our result implies a discrepancy between the experimental determination of $a_{\mu }$ and the Standard Model of 3$\sigma$.

    ↳ hep-lathep-phPRD(2017)·148 citations
20. 20*

    A systematic approach to sketch Bethe-Salpeter equation

    Si-xue Qin🇺🇸

    To study meson properties, one needs to solve the gap equation for the quark propagator and the Bethe-Salpeter (BS) equation for the meson wavefunction, self-consistently. The gluon propagator, the quark-gluon vertex, and the quark--anti-quark scattering kernel are key pieces to solve those equations. Predicted by lattice-QCD and Dyson-Schwinger analyses of QCD's gauge sector, gluons are non-perturbatively massive. In the matter sector, the modeled gluon propagator which can produce a veracious description of meson properties needs to possess a mass scale, accordingly. Solving the well-known longitudinal Ward-Green-Takahashi identities (WGTIs) and the less-known transverse counterparts together, one obtains a nontrivial solution which can shed light on the structure of the quark-gluon vertex. It is highlighted that the phenomenologically proposed anomalous chromomagnetic moment (ACM) vertex originates from the QCD Lagrangian symmetries and its strength is proportional to the magnitude of dynamical chiral symmetry breaking (DCSB). The color-singlet vector and axial-vector WGTIs can relate the BS kernel and the dressed quark-gluon vertex to each other. Using the relation, one can truncate the gap equation and the BS equation, systematically, without violating crucial symmetries, e.g., gauge symmetry and chiral symmetry.

    ↳ nucl-thhep-lathep-phnucl-exEPJ Web Conf.(2016)·11 citations
21. 21*

    The theory of local mass dimension one fermions of spin one half

    Dharam Vir Ahluwalia🇮🇳

    About a decade ago the present author in collaboration with Daniel Grumiller presented an `unexpected theoretical discovery' of spin one-half fermions with mass dimension one [JCAP 2005, PRD 2005]. In the decade that followed a significant number of groups explored intriguing mathematical and physical properties of the new construct. However, the formalism suffered from two troubling features, that of non-locality and a subtle violation of Lorentz symmetry. Here, we trace the origin of both of these issues to a hidden freedom in the definition of duals of spinors and the associated field adjoints. In the process, for the first time, we provide a quantum theory of spin one-half fermions that is free from all the mentioned issues. The interactions of the new fermions are restricted to dimension-four quartic self interaction, and also to a dimension-four coupling with the Higgs. A generalised Yukawa coupling of the new fermions with neutrinos provides an hitherto unsuspected source of lepton-number violation. The new fermions thus present a first-principle dark matter partner to Dirac fermions of the standard model of high energy physics with contrasting mass dimensions -- that of three halves for the latter versus one of the former without mutating the statistics from fermionic to bosonic.

    ↳ hep-thgr-qchep-phmath-ph+1Adv.Appl.Clifford Algebras(2017)·79 citations
22. 22*

    Hybrid Natural Inflation

    Graham G. Ross🇬🇧 · Gabriel German🇬🇧 · J. Alberto Vazquez🇺🇸

    We construct two simple effective field theory versions of {\it Hybrid Natural Inflation (HNI)} that illustrate the range of its phenomenological implications. The resulting inflationary sector potential, $V={\Delta }^4(1+a\cos (\varphi /f))$, arises naturally, with the inflaton field a pseudo-Nambu-Goldstone boson. The end of inflation is triggered by a waterfall field and the conditions for this to happen are determined. Also of interest is the fact that the slow-roll parameter $ϵ$ (and hence the tensor $r$) is a non-monotonic function of the field with a maximum where observables take universal values that determines the maximum possible tensor to scalar ratio $r$. In one of the models the inflationary scale can be as low as the electroweak scale. We explore in detail the associated HNI phenomenology, taking account of the constraints from Black Hole production, and perform a detailed fit to the Planck 2015 temperature and polarisation data.

    ↳ astro-ph.COgr-qchep-phJHEP(2016)·24 citations
23. 23*

    Electroweak interactions and dark baryons in the sextet BSM model with a composite Higgs particle

    Zoltan Fodor🇩🇪 · Kieran Holland🇺🇸 · Julius Kuti🇺🇸 · Santanu Mondal🇭🇺 · Daniel Nogradi🇭🇺 · Chik Him Wong🇩🇪

    The Electroweak interactions of a strongly coupled gauge theory are discussed with outlook beyond the Standard Model (BSM) under global and gauge anomaly constraints. The theory is built on a minimal massless fermion doublet of the SU(2) BSM flavor group (bsm-flavor) with a confining gauge force at the TeV scale in the two-index symmetric (sextet) representation of the BSM SU(3) color gauge group (bsm-color). The intriguing possibility of near-conformal sextet gauge dynamics could lead to the minimal realization of the composite Higgs mechanism with a light $0^{++}$ scalar, far separated from strongly coupled resonances of the confining gauge force in the 2-3 TeV range, distinct from Higgsless Technicolor. In previous publications we have presented results for the meson spectrum of the theory, including the light composite scalar, perhaps the emergent Higgs impostor. Here we discuss the critically important role of the baryon spectrum in the sextet model investigating its compatibility with what we know about thermal evolution of the early Universe including its galactic and terrestrial relics. For an important application, we report the first numerical results on the baryon spectrum of this theory from non-perturbative lattice simulations with baryon correlators in the staggered fermion implementation of the strongly coupled gauge sector. The quantum numbers of composite baryons and their spectroscopy from lattice simulations are required inputs for exploring dark matter contributions of the sextet BSM model, as outlined for future work.

    ↳ hep-lathep-phPRD(2016)·28 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.