Mon·Oct 31, 2016Monday·October 31, 2016

1. 01*

   Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung

   Yacine Mehtar-Tani🇺🇸 · Konrad Tywoniuk🇨🇭

   We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.

   hep-phnucl-thJHEP(2017)·128 citations
2. 02*

   Lifetime and mass of rho meson in correlation with magnetic-dimensional reduction

   Mamiya Kawaguchi🇯🇵 · Shinya Matsuzaki🇯🇵

   It is simply anticipated that in a strong magnetic configuration, the Landau quantization ceases the neutral rho meson to decay to the charged pion pair, so the neutral rho meson will be long-lived. To closely access this naive observation, we explicitly compute the charged pion-loop in the magnetic field at the one-loop level, to evaluate the magnetic dependence of the lifetime for the neutral rho meson as well as its mass.Due to the dimensional reduction induced by the magnetic field (violation of the Lorentz invariance), the polarization (spin $s_z=-1,0,+1$) modes of the rho meson, as well as the corresponding pole mass and width, are decomposed in a nontrivial manner compared to the vacuum case. To see the significance of the reduction effect, we simply take the lowest-Landau level approximation to analyze the spin-dependent rho masses and widths. We find that the "fate" of the rho meson may be more complicated because of the magnetic-dimensional reduction: as the magnetic field increases, the rho width for the spin $s_z=0$ starts to develop, reach a peak, to be vanishing at the critical magnetic field to which the folklore refers. On the other side, the decay rates of the other rhos for $s_z=-1,+1$ monotonically increase as the magnetic field develops. The correlation between the polarization dependence and the Landau-level truncation is also addressed.

   hep-phnucl-thEPJA(2017)·11 citations
3. 03*

   Automated Neutrino Jet and Top Jet Predictions at Next-to-Leading-Order with Parton Shower Matching in Effective Left-Right Symmetric Models

   Olivier Mattelaer🇧🇪 · Manimala Mitra🇮🇳 · Richard Ruiz🇬🇧

   Hadronic decays of boosted resonances, e.g., top quark jets, at hadronic super colliders are frequent predictions in TeV-scale extensions of the Standard Model of Particle Physics. In such scenarios, accurate modeling of QCD radiation is necessary for trustworthy predictions. We present the automation of fully differential, next-to-leading-order (NLO) in QCD corrections with parton shower (PS) matching for an effective Left-Right Symmetric Model (LRSM) that features $W_R^{\pm },Z_R$ gauge bosons and heavy Majorana neutrinos $N$. Publicly available universal model files require remarkably fewer user inputs for predicting benchmark collider processes than leading order LRSM constructions. We present predictions for inclusive $W_R^{\pm },Z_R$ production at the $\sqrt{s}=13$ TeV Large Hadron Collider (LHC) and a hypothetical future 100 TeV Very Large Hadron Collider (VLHC), as well as inclusive $N$ production for a hypothetical Large Hadron Electron Collider (LHeC). As a case study, we investigate at NLO+PS accuracy the properties of heavy neutrino (color-singlet) jets and top quark (color-triplet) jets from decays of high-mass $W_R$ bosons at the LHC. Contrary to top jets, we find that the kinematic properties of heavy neutrinos jets, and in particular jet mass, are resilient against the effects of parton showers and hard QCD radiation. This suggests that in searches for neutrino jets, aggressive selection cuts that would otherwise be inappropriate for top jets can be imposed with minimal signal loss.

   hep-phhep-ex44 citations
4. 04*

   Exponential parameterization of the neutrino mixing matrix - comparative analysis with different data sets and CP violation

   Konstantin Zhukovsky🇷🇺 · Anatoly Borisov🇷🇺

   The exponential parameterization of Pontecorvo-Maki-Nakagawa-Sakata mixing matrix for neutrino is used for comparative analysis of different neutrino mixing data. The UPMNS matrix is considered as the element of the SU(3) group and the second order matrix polynomial is constructed for it. The inverse problem of constructing the logarithm of the mixing matrix is addressed. In this way the standard parameterization is related to the exponential parameterization exactly. The exponential form allows easy factorization and separate analysis of the rotation and the CP violation. With the most recent experimental data on the neutrino mixing (May 2016), we calculate the values of the exponential parameterization matrix for neutrinos with account for the CP violation. The complementarity hypothesis for quarks and neutrinos is demonstrated to hold, despite significant change in the neutrino mixing data. The values of the entries of the exponential mixing matrix are evaluated with account for the actual degree of the CP violation in neutrino mixing and without it. Various factorizations of the CP violating term are investigated in the framework of the exponential parameterization.

   hep-phEPJC(2016)·8 citations
5. 05*

   Flavored Gauge Mediation with Discrete Non-Abelian Symmetries

   Lisa L. Everett🇺🇸 · Todd S. Garon🇺🇸

   We explore the model-building and phenomenology of flavored gauge mediation models of supersymmetry breaking in which the electroweak Higgs doublets and the SU(2) messenger doublets are connected by a discrete non-Abelian symmetry. The embedding of the Higgs and messenger fields into representations of this non-Abelian Higgs-messenger symmetry results in specific relations between the Standard Model Yukawa couplings and the messenger-matter Yukawa interactions. Taking the concrete example of an S(3) Higgs-messenger symmetry, we demonstrate that while the minimal implementation of this scenario suffers from a severe mu/B_mu problem that is well-known from ordinary gauge mediation, expanding the Higgs-messenger field content allows for the possibility that mu and B_mu can be separately tuned, allowing for the possibility of phenomenologically viable models of the soft supersymmetry breaking terms. We construct toy examples of this type that are consistent with the observed 125 GeV Higgs boson mass.

   hep-phPRD(2018)·7 citations
6. 06*

   Phenomenological study of extended seesaw model for light sterile neutrino

   Newton Nath🇮🇳 · Monojit Ghosh🇯🇵 · Srubabati Goswami🇮🇳 · Shivani Gupta🇦🇺

   We study the zero textures of the Yukawa matrices in the minimal extended type-I seesaw (MES) model which can give rise to $\sim$ eV scale sterile neutrinos. In this model, three right handed neutrinos and one extra singlet $S$ are added to generate a light sterile neutrino. The light neutrino mass matrix for the active neutrinos, $m_{\nu }$, depends on the Dirac neutrino mass matrix ($M_D$), Majorana neutrino mass matrix ($M_R$) and the mass matrix ($M_S$) coupling the right handed neutrinos and the singlet. The model predicts one of the light neutrino masses to vanish. We systematically investigate the zero textures in $M_D$ and observe that maximum five zeros in $M_D$ can lead to viable zero textures in $m_{\nu }$. For this study we consider four different forms for $M_R$ (one diagonal and three off diagonal) and two different forms of $(M_S)$ containing one zero. Remarkably we obtain only two allowed forms of $m_{\nu }$ ($m_{e\tau }=0$ and $m_{\tau \tau }=0$) having inverted hierarchical mass spectrum. We re-analyze the phenomenological implications of these two allowed textures of $m_{\nu }$ in the light of recent neutrino oscillation data. In the context of the MES model, we also express the low energy mass matrix, the mass of the sterile neutrino and the active-sterile mixing in terms of the parameters of the allowed Yukawa matrices. The MES model leads to some extra correlations which disallow some of the Yukawa textures obtained earlier, even though they give allowed one-zero forms of $m_{\nu }$. We show that the allowed textures in our study can be realized in a simple way in a model based on MES mechanism with a discrete Abelian flavor symmetry group $Z_8\times Z_2$.

   hep-phJHEP(2017)·34 citations
7. 07*

   Recent Progress in Lorentz and CPT Violation

   Alan Kostelecky🇺🇸

   This contribution to the CPT'16 meeting briefly highlights some of the recent progress in the phenomenology of Lorentz and CPT violation, with emphasis on research performed at the Indiana University Center for Spacetime Symmetries.

   hep-ph5 citations
8. 08*

   Non-perturbative analysis of the spectrum of meson resonances in an ultraviolet-complete composite-Higgs model

   Nicolas Bizot🇫🇷 · Michele Frigerio🇫🇷 · Marc Knecht🇫🇷 · Jean-Loïc Kneur🇫🇷

   We consider a vector-like gauge theory of fermions that confines at the multi-TeV scale, and that realizes the Higgs particle as a composite Goldstone boson. The weak interactions are embedded in the unbroken subgroup $Sp(4)$ of a spontaneously broken $SU(4)$ flavour group. The meson resonances appear as poles in the two-point correlators of fermion bilinears, and include the Goldstone bosons plus a massive pseudoscalar ${\eta }^{\prime }$, as well as scalars, vectors and axial vectors. We compute the mass spectrum of these mesons, as well as their decay constants, in the chiral limit, in the approximation where the hypercolour $Sp(2N)$ dynamics is described by four-fermion operators, à la Nambu-Jona Lasinio. By resumming the leading diagrams in the $1/N$ expansion, we find that the spin-one states lie beyond the LHC reach, while spin-zero electroweak-singlet states may be as light as the Goldstone-boson decay constant, $f\sim 1$ TeV. We also confront our results with a set of available spectral sum rules. In order to supply composite top-quark partners, the theory contains additional fermions carrying both hypercolour and ordinary colour, with an associated flavour symmetry-breaking pattern $SU(6)/SO(6)$. We identify and analyse several non-trivial features of the complete two-sector gauge theory: the 't~Hooft anomaly matching conditions; the higher-dimension operator which incorporates the effects of the hypercolour axial-singlet anomaly; the coupled mass-gap equations; the mixing between the singlet mesons of the two sectors, resulting in an extra Goldstone boson ${\eta }_0$, and novel spectral sum rules. Assuming that the strength of the four-fermion interaction is the same in the two sectors, we find that the coloured vector and scalar mesons have masses $\gtrsim 4f$, while the masses of coloured pseudo-Goldstone bosons, induced by gluon loops, are $\gtrsim 1.5f$.

   hep-phPRD(2017)·31 citations
9. 09*

   Lorentz Violation in Deep Inelastic Electron-Proton Scattering

   Enrico Lunghi🇺🇸

   Lorentz violation in the quark sector induces a sidereal time dependence in electron-proton, proton-antiproton and proton-proton cross sections. At high energies nonperturbative effects are buried in universal nucleon parton distribution functions and Lorentz violating effects are calculable in perturbation theory. We focus on deep inelastic electron-proton scattering data collected from ZEUS and H1 at HERA and show that a sideral time analysis of these events is able to set strong constraints on most of the coefficients we consider.

   hep-phhep-ex1 citation
10. 10*

    Preheating after multifield inflation with nonminimal couplings, III: Dynamical spacetime results

    Matthew P. DeCross🇺🇸 · David I. Kaiser🇺🇸 · Anirudh Prabhu🇺🇸 · Chanda Prescod-Weinstein🇺🇸 · Evangelos I. Sfakianakis🇺🇸

    This paper concludes our semi-analytic study of preheating in inflationary models comprised of multiple scalar fields coupled nonminimally to gravity. Using the covariant framework of paper I in this series, we extend the rigid-spacetime results of paper II by considering both the expansion of the universe during preheating, as well as the effect of the coupled metric perturbations on particle production. The adiabatic and isocurvature perturbations are governed by different effective masses that scale differently with the nonminimal couplings and evolve differently in time. The effective mass for the adiabatic modes is dominated by contributions from the coupled metric perturbations immediately after inflation. The metric perturbations contribute an oscillating tachyonic term that enhances an early period of significant particle production for the adiabatic modes, which ceases on a time-scale governed by the nonminimal couplings ${\xi }_I$. The effective mass of the isocurvature perturbations, on the other hand, is dominated by contributions from the fields' potential and from the curvature of the field-space manifold (in the Einstein frame), the balance between which shifts on a time-scale governed by ${\xi }_I$. As in papers I and II, we identify distinct behavior depending on whether the nonminimal couplings are small (${\xi }_I\lesssim \mathcal{O}(1)$), intermediate (${\xi }_I\sim \mathcal{O}(1-10)$), or large (${\xi }_I\ge 100$).

    ↳ astro-ph.COhep-phhep-thPRD(2018)·103 citations
11. 11*

    Electron Ion Collider: Physics and Prospects

    Hugh E. Montgomery🇺🇸

    We give an outline of the anticipated physics program for a future electron ion collider. The status and prospects for construction of such a device are discussed.

    ↳ hep-exhep-phnucl-exphysics.acc-phPoS(2017)·1 citation
12. 12*

    Dynamical dark energy: scalar fields and running vacuum

    Joan Sola🇪🇸 · Adria Gomez-Valent🇪🇸 · Javier de Cruz Perez🇪🇸

    Recent analyses in the literature suggest that the concordance $\Lambda$CDM model with rigid cosmological term, $\Lambda =$const., may not be the best description of the cosmic acceleration. The class of "running vacuum models", in which $\Lambda =\Lambda (H)$ evolves with the Hubble rate, has been shown to fit the string of $SNIa+BAO+H(z)+LSS+CMB$ data significantly better than the $\Lambda$CDM. Here we provide further evidence on the time-evolving nature of the dark energy (DE) by fitting the same cosmological data in terms of scalar fields. As a representative model we use the original Peebles & Ratra potential, $V\propto {\Phi }^{-\alpha }$. We find clear signs of dynamical DE at $\sim 4\sigma$ c.l., thus reconfirming through a nontrivial scalar field approach the strong hints formerly found with other models and parametrizations.

    ↳ astro-ph.COgr-qchep-phhep-thMod.Phys.Lett.A(2017)·90 citations
13. 13*

    Coupling constant corrections in a holographic model of heavy ion collisions

    Sašo Grozdanov🇳🇱 · Wilke van der Schee🇺🇸

    We initiate a holographic study of coupling-dependent heavy ion collisions by analysing for the first time the effects of leading-order, inverse coupling constant corrections. In the dual description, this amounts to colliding gravitational shock waves in a theory with curvature-squared terms. We find that at intermediate coupling, nuclei experience less stopping and have more energy deposited near the lightcone. When the decreased coupling results in an 80% larger shear viscosity, the time at which hydrodynamics becomes a good description of the plasma created from high energy collisions increases by 25%. The hydrodynamic phase of the evolution starts with a wider rapidity profile and smaller entropy.

    ↳ hep-thgr-qchep-phnucl-thPRL(2017)·61 citations
14. 14*

    Reconciling threshold and subthreshold expansions for pion-nucleon scattering

    D. Siemens🇩🇪 · J. Ruiz de Elvira🇩🇪 · E. Epelbaum🇩🇪 · M. Hoferichter🇺🇸 · H. Krebs🇩🇪 · B. Kubis🇩🇪 · U.-G. Meißner🇩🇪

    Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion-nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the $\Delta (1232)$ as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the $\Delta$ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the $\Delta$-less theory the resummation of $1/m_N$ corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.

    ↳ nucl-thhep-phPLB(2017)·124 citations
15. 15*

    Holographic Isotropisation in Gauss-Bonnet Gravity

    Tomas Andrade🇬🇧 · Jorge Casalderrey-Solana🇬🇧 · Andrej Ficnar🇬🇧

    We study holographic isotropisation of homogeneous, strongly coupled, non-Abelian plasmas in Gauss-Bonnet gravity with a negative cosmological constant. We focus on small values of the Gauss-Bonnet coupling parameter ${\lambda }_{GB}$ and linearise the equations of motion around a time-dependent background solution with ${\lambda }_{GB}=0$. We numerically solve the linearised equations and show that the entire time evolution of the pressure anisotropy can be well approximated by the linear in ${\lambda }_{GB}$ corrections to the quasinormal mode expansion, even in the cases of high anisotropy. We finally show that, quite generally, the time evolution of the pressure anisotropy with the Gauss-Bonnet term is approximately {\it shifted} with respect to the evolution without it, with the sign of the shift being directly related to the sign of the ${\lambda }_{GB}$ parameter. This suggests that finite coupling corrections generically {\it increase} the isotropisation time of strongly coupled plasmas.

    ↳ hep-thgr-qchep-phJHEP(2017)·42 citations
16. 16*

    ${\Lambda }_c{\Sigma }_c\pi$ coupling and ${\Sigma }_c\to {\Lambda }_c\pi$ decay in lattice QCD

    K. U. Can🇯🇵 · G. Erkol🇹🇷 · M. Oka🇯🇵 · T. T. Takahashi🇯🇵

    We evaluate the ${\Lambda }_c{\Sigma }_c\pi$ coupling constant ($G_{{\Lambda }_c{\Sigma }_c\pi }$) and the width of the strong decay ${\Sigma }_c\to {\Lambda }_c\pi$ in 2+1 flavor lattice QCD on four different ensembles with pion masses ranging from 700 MeV to 300 MeV. We find $G_{{\Lambda }_c{\Sigma }_c\pi }=18.332(1.476{)}_{stat.}(2.171{)}_{syst.}$ and the decay width $\Gamma ({\Sigma }_c\to {\Lambda }_c\pi )=1.65(28{)}_{stat.}(30{)}_{syst.}$~MeV on the physical quark-mass point, which is in agreement with the recent experimental determination.

    ↳ hep-lathep-phPLB(2017)·10 citations
17. 17*

    Scalar-tensor linear inflation

    Michal Artymowski🇵🇱 · Antonio Racioppi🇪🇪

    We investigate two approaches to non minimally coupled gravity theories which present linear inflation as attractor solution: a) the scalar-tensor theory approach, where we look for a scalar-tensor theory that would restore results of linear inflation in the strong coupling limit for any form of the non-minimal coupling to gravity of the form of $f(\phi )R/2$; b) the particle physics approach, where we motivate the form of the Jordan frame potential by the loop corrections to the inflaton field. In both cases the Jordan frame potentials are modifications of the induced inflation, but instead of the Starobinsky attractor they lead to the linear inflation in the strong coupling limit.

    ↳ astro-ph.COgr-qchep-phJCAP(2017)·38 citations
18. 18*

    Inconsistency of the interactions between pseudoscalar, spinor and Rarita-Schwinger fields

    D. Badagnani🇦🇷 · A. Mariano🇦🇷 · C. Barbero🇦🇷

    We perform the Dirac quantization of RS fields interacting with a spinor and the first derivative of a pseudoscalar field. We achieve the calculations for two forms of this interaction: first we review the conventional coupling of lowest derivative order, reproducing the well known inconsistencies in its anticommutator algebra. Then, we perform the analysis on the next order term popularly known as spin 3/2 gauge invariant interaction, which is claimed to be free of these inconsistencies. Nevertheless we find that the direct application of the Dirac formalism leads to inconsistencies in complete analogy to the previous case. This is of high relevance in the particle phenomenology field, where these interactions are used to interpret experimental data involving Delta(1232) resonances.

    ↳ nucl-thhep-ph0 citations
19. 19*

    Weyl Current, Scale-Invariant Inflation and Planck Scale Generation

    Pedro G. Ferreira🇬🇧 · Christopher T. Hill🇺🇸 · Graham G. Ross🇬🇧

    Scalar fields, ${\varphi }_i$ can be coupled non-minimally to curvature and satisfy the general criteria: (i) the theory has no mass input parameters, including the Planck mass; (ii) the ${\varphi }_i$ have arbitrary values and gradients, but undergo a general expansion and relaxation to constant values that satisfy a nontrivial constraint, $K({\varphi }_i)=$ constant; (iii) this constraint breaks scale symmetry spontaneously, and the Planck mass is dynamically generated; (iv) there can be adequate inflation associated with slow roll in a scale invariant potential subject to the constraint; (v) the final vacuum can have a small to vanishing cosmological constant (vi) large hierarchies in vacuum expectation values can naturally form; (vii) there is a harmless dilaton which naturally eludes the usual constraints on massless scalars. These models are governed by a global Weyl scale symmetry and its conserved current, $K_{\mu }$ . At the quantum level the Weyl scale symmetry can be maintained by an invariant specification of renormalized quantities.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2017)·117 citations
20. 20*

    Testing the hadronic spectrum in the strange sector

    Paolo Parotto🇺🇸

    Heavier resonances are continually being added to the hadronic spectrum from the Particle Data Group that follow an exponentially increasing mass spectrum. However, it has been suggested that even further states predicted from Quark Models are needed in the hadronic spectrum in order to improve the agreement between the hadron resonance gas model predictions and lattice QCD data. We find that the inclusion of such states with extrapolated branching ratios slightly decreases the freezeout temperature. To eliminate ambiguities, we introduce a first principle method to extract the freeze-out temperature for charged kaons from experimental data, which yields a lower bound of $T_{\text{fo}}\gtrsim$145 MeV for the highest collision energy at RHIC.

    ↳ nucl-thhep-lathep-phJ.Phys.Conf.Ser.(2017)·0 citations
21. 21*

    Biased Tracers in Redshift Space in the EFT of Large-Scale Structure

    Ashley Perko🇺🇸 · Leonardo Senatore🇺🇸 · Elise Jennings🇺🇸 · Risa H. Wechsler🇺🇸

    The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a novel formalism that is able to accurately predict the clustering of large-scale structure (LSS) in the mildly non-linear regime. Here we provide the first computation of the power spectrum of biased tracers in redshift space at one loop order, and we make the associated code publicly available. We compare the multipoles $\ell =0,2$ of the redshift-space halo power spectrum, together with the real-space matter and halo power spectra, with data from numerical simulations at $z=0.67$. For the samples we compare to, which have a number density of $\bar{n}=3.8\cdot 10^{-2}(h{\mathrm{Mpc}}^{-1}{)}^3$ and $\bar{n}=3.9\cdot 10^{-4}(h{\mathrm{Mpc}}^{-1}{)}^3$, we find that the calculation at one-loop order matches numerical measurements to within a few percent up to $k\simeq 0.43h{\mathrm{Mpc}}^{-1}$, a significant improvement with respect to former techniques. By performing the so-called IR-resummation, we find that the Baryon Acoustic Oscillation peak is accurately reproduced. Based on the results presented here, long-wavelength statistics that are routinely observed in LSS surveys can be finally computed in the EFTofLSS. This formalism thus is ready to start to be compared directly to observational data.

    ↳ astro-ph.COgr-qchep-phhep-th214 citations
22. 22*

    Multiparton interactions: From pp to pA

    Christian Bierlich🇸🇪

    In the process of understanding nuclear collisions, reliable extrapolations from pp collisions, based on Glauber models, are highly desirable, though seldomly accurate. We review the inclusion of diffractive excitations and argue that they provide an important contribution to centrality observables in pA collisions. We present a method for distinguishing between diffractively and non-diffractively wounded nucleons, and a proof-of-principle for an extrapolation of multiparton interaction models built on this.

    ↳ nucl-thhep-phNucl.Part.Phys.Proc.(2017)·0 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.