Mon·Jan 30, 2017Monday·January 30, 2017

1. 01*

   Collinear parton distributions and the structure of the nucleon sea in a light-front meson-cloud model

   S. Kofler (Graz U.)🇦🇹 · B. Pasquini (Pavia U. & INFN, Pavia)🇮🇹

   The unpolarized, helicity and transversity parton distribution functions of the nucleon are studied within a convolution model where the bare nucleon is dressed by its virtual meson cloud. Using light-front time-ordered perturbation theory, the Fock states of the physical nucleon are expanded in a series involving a bare nucleon and two-particle, meson-baryon, states. The bare baryons and mesons are described with light-front wave functions (LFWFs) for the corresponding valence-parton components. Using a representation in terms of overlap of LFWFs, the role of the non-perturbative antiquark degrees of freedom and the valence quark contribution at the input scale of the model is discussed for the leading-twist collinear parton distributions. After introducing perturbative QCD effects through evolution to experimental scales, the results are compared with available data and phenomenological extractions. Predictions for the nucleon tensor charge are also presented, finding a very good agreement with recent phenomenological extractions.

   hep-phnucl-thPRD(2017)·15 citations
2. 02*

   Manifestations of minimum-bias dijets in high-energy nuclear collisions

   Thomas A. Trainor🇺🇸

   Dijets observed near midrapidity in high-energy nuclear collisions result from large-angle scattering of low-$x$ partons (gluons) within projectile hadrons as a signature manifestation of QCD. Within the same collisions it has been claimed that hydrodynamic flows (radial, elliptic and "higher harmonic" flows) carried by a dense QCD medium or quark-gluon plasma (QGP) dominate the observed hadronic final state. The flow-QGP narrative is imposed {\em a priori} on primary particle data, and of all possible analysis methods a subset A that seems to support that narrative is preferred. The present study explores an alternative minimum-bias (MB) jet narrative -- quantitative correspondence of MB dijet manifestations in the hadronic final state with measured {\em isolated jet} properties. The latter incorporates a different set of methods B that emerge from inductive study of primary particle data without {\em a priori} assumptions. The resulting system of methods and data manifestations is represented by a two-component (soft + hard) model (TCM) of hadron production. A survey of methods reveals that type A tends to discard substantial information carried by primary particle data whereas type B retains almost all information in both primary particle data from nuclear collisions and from isolated jets. The main goal of the present study is a review of MB dijet contributions to high-energy collisions in small and large systems relative to measured isolated-jet properties. Representative analysis methods from types A and B are compared in the context of MB jet manifestations. This study suggests that at least some data features commonly attributed to flows actually result from MB dijets and thereby challenges the flow-QGP narrative.

   hep-ph17 citations
3. 03*

   Closing in on Resonantly Produced Sterile Neutrino Dark Matter

   John F. Cherry🇺🇸 · Shunsaku Horiuchi🇺🇸

   We perform an exhaustive scan of the allowed resonant production regime for sterile neutrino dark matter in order to improve constraints for dark matter structures which arise from the non-thermal sterile neutrino energy spectra. Small-scale structure constraints are particularly sensitive to large lepton asymmetries/small mixing angles which result in relatively warmer sterile neutrino momentum distributions. We revisit Milky Way galaxy subhalo count constraints and combine them with recent searches for X-ray emission from sterile neutrino decays. Together they rule out models outside the mass range 7.0 keV < m_nu_s < 36 keV and lepton asymmetries smaller than 15 x 10-6 per unit entropy density at 95 percent CI or greater. We also find that while a portion of the parameter space remains unconstrained, the combination of subhalo counts and X-ray data indicate the candidate 3.55 keV X-ray line signal potentially originating from a 7.1 keV sterile neutrino decay to be disfavored at 93 percent CI.

   hep-phastro-ph.COPRD(2017)·89 citations
4. 04*

   Heavy neutrino potential for neutrinoless double beta decay

   Yoritaka Iwata🇯🇵

   Heavy neutrino potential for neutrinoless double beta decay is studied with focusing on its statistical property. The existence condition for heavy neutrinos is also presented. In particular sterile neutrinos are possible candidate for heavy nuetrinos. The statistics provide a gross view of understanding amplitude of constitutional components of the nuclear matrix element.

   hep-phnucl-thPoS(2017)·1 citation
5. 05*

   Derivation of the effective Chiral Lagrangian for pseudoscalar, scalar, vector and axial-vector mesons from QCD

   Ke Ren🇨🇳 · Hui-Feng Fu🇨🇳 · Qing Wang🇨🇳

   A previous formal derivation of the effective chiral Lagrangian for low-lying pseudoscalar mesons from first-principles QCD without approximations [Wang et al., Phys. Rev. D61, (2000) 54011] is generalized to further include scalar, vector, and axial-vector mesons. In the large Nc limit and with an Abelian approximation, we show that the properties of the newly added mesons in our formalism are determined by the corresponding underlying fundamental homogeneous Bethe--Salpeter equation in the ladder approximation, which yields the equations of motion for the scalar, vector, and axial-vector meson fields at the level of an effective chiral Lagrangian. The masses appearing in the equations of motion of the meson fields are those determined by the corresponding Bethe--Salpeter equation.

   hep-phhep-thPRD(2017)·9 citations
6. 06*

   Condensation of neutral vector bosons with magnetic moment

   Gretel Quintero Angulo🇨🇺 · Aurora Perez Martinez🇨🇺 · Hugo Perez Rojas🇨🇺

   We study the equation of motion of neutral vector bosons bearing a magnetic moment (MM). The effective rest mass of vector bosons is a decreasing function of the magnetic field intensity. Consequently a diffuse condensation of the bosons appears below a critical value of the field. For typical values of densities and magnetic fields the magnetization is positive and the neutral boson system can maintain a magnetic field self-consistently. A discussion of the relevance in astrophysics is presented.

   hep-phInt.J.Mod.Phys.Conf.Ser.(2017)·7 citations
7. 07*

   Integrated and Differential Accuracy in Resummed Cross Sections

   Daniele Bertolini🇺🇸 · Mikhail P. Solon🇺🇸 · Jonathan R. Walsh🇺🇸

   Standard QCD resummation techniques provide precise predictions for the spectrum and the cumulant of a given observable. The integrated spectrum and the cumulant differ by higher-order terms which, however, can be numerically significant. In this paper we propose a method, which we call the $\sigma \text{-improved}$ scheme, to resolve this issue. It consists of two steps: (i) include higher-order terms in the spectrum to improve the agreement with the cumulant central value, and (ii) employ profile scales that encode correlations between different points to give robust uncertainty estimates for the integrated spectrum. We provide a generic algorithm for determining such profile scales, and show the application to the thrust distribution in $e^{+}{e}^{-}$ collisions at NLL${}^{\prime }$+NLO and NNLL${}^{\prime }$+NNLO.

   hep-phPRD(2017)·15 citations
8. 08*

   Neutrino masses, mixing, and leptogenesis in an S3 model

   Arturo Alvarez Cruz🇲🇽 · Myriam Mondragón🇲🇽

   In this work we use previous results on the masses and mixing of neu- trinos of an S3 model with three right-handed Majorana neutrinos and three Higgs doublets, to reduce one parameter in the case when two of the right-handed neutrinos are mass degenerate. We derive a new param- eterization for the VP M N S mixing matrix, with a new set of parameters, in the more general case where the right-handed neutrino masses are dif- ferent. With these results, we calculate leptogenesis and the associated baryogenesis in the model in the two different scenarios. We show that it is possible to have enough leptogenesis to explain the baryonic asymmetry with right-handed neutrino masses above 10^{6} GeV.

   hep-ph21 citations
9. 09*

   Nonperturbative SU(3) thermodynamics and the phase transition

   N.O. Agasian🇷🇺 · M.S. Lukashov🇷🇺 · Yu.A. Simonov🇷🇺

   The $SU(3)$ equation of state ($P(T),s(T),I(T)$) are calculated within the Field Correlator Method both in the confined and the deconfined phases. The basic dynamics in our approach is contained in the vacuum correlators, both of the colorelectric (CE) and colormagnetic (CM) types, which ensure CE and CM confinement below $T_c$ and CM confinement and Polyakov loops above $T_c$. The resulting values of $T_c$ and $P(T),I(T)$, $s(T)$ are in good agreement with lattice measurements.

   hep-phhep-latEPJA(2017)·26 citations
10. 10*

    Perturbative Power Counting, Lowest-Index Operators and Their Renormalization in Standard Model Effective Field Theory

    Yi Liao🇨🇳 · Xiao-Dong Ma🇨🇳

    We study two aspects of higher dimensional operators in standard model effective field theory. We first introduce a perturbative power counting rule for the entries in the anomalous dimension matrix of operators with equal mass dimension. The power counting is determined by the number of loops and the difference of the indices of the two operators involved, which in turn is defined by assuming that all terms in the standard model Lagrangian have an equal perturbative power. Then we show that the operators with the lowest index are unique at each mass dimension $d$, i.e., $(H^{†}H{)}^{d/2}$ for even $d\ge 4$, and $(L^TϵH)C(L^TϵH{)}^T(H^{†}H{)}^{(d-5)/2}$ for odd $d\ge 5$. Here $H,L$ are the Higgs and lepton doublet, and $ϵ,C$ the antisymmetric matrix of rank two and the charge conjugation matrix, respectively. The renormalization group running of these operators can be studied separately from other operators of equal mass dimension at the leading order in power counting. We compute their anomalous dimensions at one loop for general $d$ and find that they are enhanced quadratically in $d$ due to combinatorics. We also make connections with classification of operators in terms of their holomorphic and anti-holomorphic weights.

    hep-phCommun.Theor.Phys.(2018)·5 citations
11. 11*

    Reopening the Higgs portal for Singlet Scalar Dark Matter

    J. Alberto Casas🇪🇸 · David G. Cerdeño🇬🇧 · Jesus M. Moreno🇪🇸 · Javier Quilis🇪🇸

    A real singlet scalar, connected to the Standard Model sector through a portal with the Higgs boson, is one of the simplest and most popular models for dark matter (DM). However, the experimental advances in direct and indirect DM searches, together with the latest results from the LHC, have ruled out vast areas of the parameter space of this scenario, and are expected to probe it completely within the next years, ruling it out if no signal is found. Motivated by the simplicity of this model, in this article we address a minimal, renormalizable extension that could evade detection, consisting of the addition of an extra real singlet scalar field in the dark sector. We analyze the physical constraints on the model and show that the new annihilation and/or coannihilation channels involving the extra singlet allow to reproduce the correct DM relic abundance while avoiding the bounds from direct and indirect searches for any DM mass above 50 GeV. We also show that, in some interesting regions of the parameter space, the extra particle can be integrated-out, leaving a "clever" effective theory (just involving the DM particle and the Higgs), that essentially reproduces the results.

    hep-phastro-ph.COJHEP(2017)·135 citations
12. 12*

    Two roads to hydrodynamic effective actions: a comparison

    Felix M. Haehl🇨🇦 · R. Loganayagam🇮🇳 · Mukund Rangamani🇺🇸

    We make a detailed comparison between two attempts in recent years to construct hydrodynamic effective actions: we compare our work [1-7] with that of Crossley-Glorioso-Liu [8] and Glorioso-Liu [9]. The general philosophy espoused by the two approaches has a degree of overlap, despite various differences. We will try to outline the similarities to eke out the general lessons that have been uncovered, hoping that it will ease the access to the subject for interested readers.

    ↳ hep-thcond-mat.stat-mechhep-phphysics.flu-dyn29 citations
13. 13*

    Axion excursions of the landscape during inflation

    Gonzalo A. Palma🇨🇱 · Walter Riquelme🇨🇱

    Because of their quantum fluctuations, axion fields had a chance to experience field excursions traversing many minima of their potentials during inflation. We study this situation by analyzing the dynamics of an axion-spectator field $\psi$, present during inflation, with a periodic potential given by $v(\psi )={\Lambda }^4[1-\cos (\psi /f)]$. By assuming that the vacuum expectation value of the field is stabilized at one of its minima, say $\psi =0$, we compute every $n$-point correlation function of $\psi$ up to first order in ${\Lambda }^4$ using the in-in formalism. This computation allows us to identify the distribution function describing the probability of measuring $\psi$ at a particular amplitude during inflation. Because $\psi$ is able to tunnel between the barriers of the potential, we find that the probability distribution function consists of a non-Gaussian multimodal distribution such that the probability of measuring $\psi$ at a minimum of $v(\psi )$ different from $\psi =0$ increases with time. As a result, at the end of inflation, different patches of the Universe are characterized by different values of the axion field amplitude, leading to important cosmological phenomenology: (a) Isocurvature fluctuations induced by the axion at the end of inflation could be highly non-Gaussian. (b) If the axion defines the strength of standard model couplings, then one is led to a concrete realization of the multiverse. (c) If the axion corresponds to dark matter, one is led to the possibility that, within our observable Universe, dark matter started with a nontrivial initial condition, implying novel signatures for future surveys.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2017)·11 citations
14. 14*

    Full jet in quark-gluon plasma with hydrodynamic medium response

    Yasuki Tachibana🇨🇳 · Ning-Bo Chang🇨🇳 · Guang-You Qin🇨🇳

    We study the nuclear modifications of full jets and their structures in relativistic heavy-ion collisions including the effect of hydrodynamic medium response to jet quenching. To study the evolutions of the full jet shower and the traversed medium with energy and momentum exchanges between them, we formulate a coupled jet-fluid model consisting of a set of jet transport equations and relativistic hydrodynamics equations with source terms. In our model, the full jet shower interacts with the medium and gets modified via collisional and radiative processes during the propagation. Meanwhile, the energy and momentum are deposited from the jet shower to the medium and then evolve with the medium hydrodynamically. The full jet defined by a cone size in the final state includes the jet shower and the particles produced from jet-induced flow. We apply our model to calculate the full jet energy loss and the nuclear modifications of jet rate and shape in Pb+Pb collisions at $2.76\mathrm{A}\mathrm{TeV}$. It is found that the inclusion of jet-induced flow contribution leads to stronger jet-cone size dependence for jet energy loss and jet suppression. Jet-induced flow also has a significant contribution to jet shape function and dominates at large angles away from the jet axis.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2017)·166 citations
15. 15*

    Top-quark and Higgs boson perspectives at heavy-ion colliders

    David d'Enterria🇨🇭

    The perspectives for measuring the top quark and the Higgs boson in nuclear collisions at the LHC and Future Circular Collider (FCC) are summarized. Perturbative QCD calculations at (N)NLO accuracy, including nuclear parton distribution functions, are used to determine their cross sections and visible yields after standard analysis cuts in PbPb and pPb collisions at the LHC ($\sqrt{s_{NN}}$ = 5.5, 8.8 TeV) and FCC ($\sqrt{s_{NN}}$ = 39, 63 TeV). In their "cleanest" decay channels, $\mathrm{t}\bar{\mathrm{t}}\to \mathrm{b}\bar{\mathrm{b}}2\mathrm{\ell }2\nu$ and $\mathrm{H}\to \gamma \gamma ,4\mathrm{\ell }$, about 10${}^3$ ($10^5$) top-quark and 10 (10${}^3$) Higgs-boson events are expected at the LHC (FCC) for their total nominal integrated luminosities. Whereas the $\mathrm{t}\bar{\mathrm{t}}$ observation is clearcut at both colliders, evidence for Higgs production, perfectly possible at the FCC, requires integrating $\times$30 more luminosities at the LHC.

    ↳ hep-exhep-phnucl-exnucl-thNucl.Part.Phys.Proc.(2017)·18 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.