Wed·Jan 27, 2016Wednesday·January 27, 2016

1. 01*

   Wgamma and Zgamma production at the LHC in NNLO QCD

   Massimiliano Grazzini🇨🇭 · Stefan Kallweit🇩🇪 · Dirk Rathlev🇩🇪

   We consider the production of Wgamma and Zgamma pairs at the LHC, and report on the fully differential computation of next-to-next-to-leading order (NNLO) corrections in QCD perturbation theory. The calculation includes leptonic vector-boson decays with the corresponding spin correlations, off-shell effects and final-state photon radiation. We present numerical results for pp collisions at 7 TeV, and compare them with available ATLAS data. In the case of Zgamma production, the impact of NNLO corrections is generally moderate, ranging from 8% to 17%, depending on the applied cuts. In the case of Wgamma production, the NNLO effects are more important, and range from 19% to 26%, thereby improving the agreement of the theoretical predictions with the data. As expected, a veto against jets significantly reduces the impact of QCD radiative corrections.

   hep-phPoS(2016)·6 citations
2. 02*

   LHC probes of TeV-scale scalars in $\mathrm{SO}(10)$ grand unification

   Ufuk Aydemir🇸🇪 · Tanumoy Mandal🇸🇪

   We investigate the possibility of TeV-scale scalars as low energy remnants arising in the non-supersymmetric $\mathrm{SO}(10)$ grand unification framework where the field content is minimal. We consider a scenario where the $\mathrm{SO}(10)$ gauge symmetry is broken into the gauge symmetry of the Standard Model (SM) through multiple stages of symmetry breaking, and a colored and hypercharged scalar $\chi$ picks a TeV-scale mass in the process. The last stage of the symmetry breaking occurs at the TeV scale where the left-right symmetry, i.e. $\mathrm{SU}(2{)}_L\otimes \mathrm{SU}(2{)}_R\otimes \mathrm{U}(1{)}_{B-L}\otimes \mathrm{SU}(3{)}_C$, is broken into that of the SM by a singlet scalar field $\mathcal{S}$ of mass $M_{\mathcal{S}}\sim 1$ TeV, which is a component of an $\mathrm{SU}(2{)}_R$-triplet scalar field, acquiring a TeV-scale vacuum expectation value. For the LHC phenomenology, we consider a scenario where $\mathcal{S}$ is produced via gluon-gluon fusion through loop interactions with $\chi$ and also decays to a pair of SM gauge bosons through $\chi$ in the loop. We find that the parameter space is heavily constrained from the latest LHC data. We use a multivariate analysis to estimate the LHC discovery reach of $\mathcal{S}$ into the diphoton channel.

   hep-phAdv.High Energy Phys.(2017)·48 citations
3. 03*

   Inelastic WIMP-nucleus scattering to the first excited state in ${}^{125}$Te

   J. D. Vergados (University of Ioannina, Ioannina, Greece)🇦🇺 · F.T. Avignone III (University of South Carolina, Columbia, SC, USA)🇺🇸 · M. Kortelainen (University of Jyvaskyla, Finland)🇫🇮 · P. Pirinen (University of Jyvaskyla, Finland)🇫🇮 · P. C. Srivastava (Indian Institute of Technology, Roorkee, India)🇮🇳 · J. Suhonen (University of Jyvaskyla, Finland)🇫🇮 · A. W. Thomas (ARC Centre of Excellence in Particle Physics at the Terascale, University of Adelaide, Australia)🇦🇺

   The direct detection of dark matter constituents, in particular the weakly interacting massive particles (WIMPs), is considered central to particle physics and cosmology. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Examples considered previously were the first excited states of ${}^{127}$I and ${}^{129}$Xe and ${}^{83}$Kr. Here we examine ${}^{125}$Te, which offers some advantages and is currently being considered as a target.In all these cases the extra signature of the gamma rays following the de-excitation of these states has definite advantages over the purely nuclear recoil and, in principle, such a signature can be exploited experimentally. A brief discussion of the experimental feasibility is given in the context of the CUORE experiment.

   hep-phJ.Phys.G(2016)·12 citations
4. 04*

   Diboson excess and $Z^{\prime }$-predictions via left-right non-linear Higgs

   Jing Shu🇨🇳 · Juan Yepes🇨🇳

   The excess events reported by the ATLAS Collaboration in the $WZ$-final state, and by the CMS Collaboration in the $e^{+}{e}^{-}jj$, $Wh$ and $jj$-final states, may be induced by the decays of a heavy boson $W^{\prime }$ in the 1.8-2 TeV mass range, here modelled via the larger local group $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ in a non-linear dynamical Higgs scenario. The $W^{\prime }$-production cross section at the 13 TeV LHC is around 700-1200 fb. This framework also predicts a heavy $Z^{\prime }$ boson with a mass of 2.5-4 TeV, and some decay channels testable in the LHC Run II. We determine the cross section times branching fractions for the dijet, dilepton and top-pair $Z^{\prime }$-decay channels at the 13 TeV LHC around 2.3, 7.1, 70.2 fb respectively, for $M_{Z^{\prime }}=2.5$ TeV, while one/two orders of magnitude smaller for the dijet/dilepton and top-pair modes at $M_{Z^{\prime }}=4$ TeV. Non-zero contributions from the effective operators, and the underlying Higgs sector of the model, will induce sizeable enhancement in the $W^{+}{W}^{-}$ and $Zh$-final states that could be probed in the future LHC Run II.

   hep-phMod.Phys.Lett.A(2016)·16 citations
5. 05*

   Recent developments in Neutrino Physics

   Davide Meloni🇮🇹

   We discuss the recent progress in neutrino physics in the following fields: (i) interpretation of the short and long neutrino oscillation data in terms of neutrino flavor transitions; (ii) models for neutrino masses and mixings.

   hep-ph0 citations
6. 06*

   Impact of Gravity on Vacuum Stability

   Vincenzo Branchina🇮🇹 · Emanuele Messina🇮🇹 · Dario Zappala🇮🇹

   In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed that a strong gravitational field can stabilize the false vacuum, suppressing the formation of true vacuum bubbles. This result is obtained for the case when the energy density difference between the two vacua is small, the so called thin wall regime, but is considered of more general validity. Here we show that when this condition does not hold, however, {\it a strong gravitational field (Planckian physics) does not necessarily induce a total suppression of true vacuum bubble nucleation}. Contrary to common expectations then, gravitational physics at the Planck scale {\it does not stabilize the false vacuum}. These results are of crucial importance for the stability analysis of the electroweak vacuum and for searches of new physics beyond the Standard Model.

   hep-phEPL(2016)·44 citations
7. 07*

   New mechanisms for double charmed meson production at the LHCb

   Rafal Maciula🇵🇱 · Vladimir A. Saleev🇷🇺 · Alexandra V. Shipilova🇷🇺 · Antoni Szczurek🇵🇱

   We discuss production of $D^0{D}^0$ (and ${\bar{D}}^0{\bar{D}}^0$) pairs related to the LHCb Collaboration results for $\sqrt{s}$ = 7 TeV in proton-proton scattering. We consider double-parton scattering (DPS) mechanisms of double $c\bar{c}$ production and subsequent $cc\to D^0{D}^0$ hadronization as well as double $g$ and mixed $gc\bar{c}$ production with $gg\to D^0{D}^0$ and $gc\to D^0{D}^0$ hadronization calculated with the help of the scale-dependent hadronization functions of Kniehl et al. Single-parton scattering (SPS) mechanism of digluon production is also taken into account. We compare our results with several correlation observables in azimuthal angle ${\phi }_{D^0{D}^0}$ between $D^0$ mesons or in dimeson invariant mass $M_{D^0{D}^0}$. The inclusion of new mechanisms with $g\to D^0$ fragmentation leads to larger cross sections, than when including only DPS mechanism with standard scale-independent $cc\to D^0{D}^0$ fragmentation functions. Some consequences of the presence of the new mechanisms are discussed. In particular a larger ${\sigma }_{eff}$ is needed to describe the LHCb data. There is a signature that ${\sigma }_{eff}$ may depend on transverse momentum of $c$ quarks and/or $\bar{c}$ antiquarks.

   hep-phhep-exPLB(2016)·40 citations
8. 08*

   Electroproduction ratios of Baryon-Meson states and Strangeness Suppression

   E. Santopinto🇮🇹 · R. Bijker🇲🇽 · H. García-Tecocoatzi🇲🇽

   We describe the electroproduction ratios of baryon-meson states from nucleon, inferring from the sea quarks in the nucleon using an extension of the quark model that takes into account the sea. As a result we provide, with no adjustable parameters, the predictions of ratios of exclusive meson-baryon final states:$\Lambda K^{+}$, ${\Sigma }^{\ast }K$, $\Sigma K$, $p{\pi }^0$, and $n{\pi }^{+}$. These predictions are in agreement with the new Jlab experimental data showing that sea quarks play an important role in the electroproduction. We also predicted further ratios of exclusive reactions that can be measured and tested in future experiments. In particular, we suggested new experiments on deuterium and tritium. Such measurements can provide crucial test of different predictions concerning the structure of nucleon and its sea quarks helping to solve an outstanding problem. Finally, we computed the so called strangeness suppression factor, ${\lambda }_s$, that is the suppression of strange quark-antiquarks compared to nonstrange pairs, and we found that our finding with this simple extension of the quark model is in good agreement with the results of Jlab and CERN experiments.

   hep-phPLB(2016)·17 citations
9. 09*

   Hadron diffractive scattering at ultrahigh energies and coulomb interaction

   V.V. Anisovich🇷🇺 · V.A. Nikonov🇷🇺

   We study the interplay of hadronic and Coulomb interactions for $pp$ scattering at LHC energies on the basis of the previous determination of the real part of the amplitude [{\it V.V. Anisovich, V.A. Nikonov, J. Nyiri}, Int. J. Mod. Phys. A{\bf 30}, 1550188 (2015)]. The interference of hadron and Coulomb interactions is discussed in terms of the $K$-matrix function technique. Supposing the black disk mode for the asymptotic interaction of hadrons, we calculate interference effects for the energies right up to $\sqrt{s}=10^6$ TeV. It turns out that the real part of the amplitude is concentrated in the impact parameter space at the border of the black disk that results in a growth of interplay effects with the energy increase.

   hep-phMod.Phys.Lett.A(2016)·1 citation
10. 10*

    Resummed differential cross sections for top-quark pairs at the LHC

    Benjamin D. Pecjak🇬🇧 · Darren J. Scott🇬🇧 · Xing Wang🇨🇳 · Li Lin Yang🇨🇳

    We present state of the art resummation predictions for differential cross sections in top-quark pair production at the LHC. They are derived from a formalism which allows the simultaneous resummation of both soft and small-mass logarithms, which endanger the convergence of fixed-order perturbative series in the boosted regime, where the partonic center-of-mass energy is much larger than the mass to the top quark. We combine such a double resummation at NNLL${}^{\prime }$ accuracy with standard soft-gluon resummation at NNLL accuracy and with NLO calculations, so that our results are applicable throughout the whole phase space. We find that the resummation effects on the differential distributions are significant, bringing theoretical predictions into better agreement with experimental data compared to fixed-order calculations. Moreover, such effects are not well described by the NNLO approximation of the resummation formula, especially in the high-energy tails of the distributions, highlighting the importance of all-orders resummation in dedicated studies of boosted top production.

    hep-phPRL(2016)·65 citations
11. 11*

    Kinetic freeze-out temperature and flow velocity extracted from transverse momentum spectra of final-state light flavor particles produced in collisions at RHIC and LHC

    Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸

    The transverse momentum spectra of final-state light flavor particles produced in proton-proton (p-p), copper-copper (Cu-Cu), gold-gold (Au-Au), lead-lead (Pb-Pb), and proton-lead (p-Pb) collisions for different centralities at relativistic heavy ion collider (RHIC) and large hadron collider (LHC) energies are studied in the framework of a multisource thermal model. The experimental data measured by the STAR, CMS, and ALICE Collaborations are consistent with the results calculated by the multi-component Erlang distribution and Tsallis Statistics. The effective temperature and real temperature (kinetic freeze-out temperature) of interacting system at the stage of kinetic freeze-out, the mean transverse flow velocity and mean flow velocity of particles, and the relationships between them are extracted. The dependences of effective temperature and mean (transverse) momentum on rest mass, moving mass, centrality, and center-of-mass energy, and the dependences of kinetic freeze-out temperature and mean (transverse) flow velocity on centrality, center-of-mass energy, and system size are obtained.

    hep-phnucl-exnucl-thEPJA(2016)·43 citations
12. 12*

    Event patterns extracted from transverse momentum and rapidity spectra of Z bosons and quarkonium states produced in pp and Pb-Pb collisions at LHC

    Ya-Hui Chen🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸

    Transverse momentum ($p_T$) and rapidity ($y$) spectra of $Z$ bosons and quarkonium states (some charmonium $c\bar{c}$ mesons such as $J/\psi$ and $\psi (2S)$, and some bottomonium $b\bar{b}$ mesons such as ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$) produced in proton-proton ($pp$) and lead-lead (Pb-Pb) collisions at the large hadron collider (LHC) are uniformly described by a hybrid model of two-component Erlang distribution for $p_T$ spectrum and two-component Gaussian distribution for $y$ spectrum. The former distribution results from a multisource thermal model, and the latter one results from the revised Landau hydrodynamic model. The modelling results are in agreement with the experimental data measured in $pp$ collisions at center-of-mass energies $\sqrt{s}=2.76$ and 7 TeV, and in Pb-Pb collisions at center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=2.76$ TeV. Based on the parameter values extracted from $p_T$ and $y$ spectra, the event patterns (particle scatter plots) in two-dimensional $p_T$-$y$ space and in three-dimensional velocity space are obtained.

    hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2016)·6 citations
13. 13*

    Frontiers of QCD with Precision nPDFs

    Aleksander Kusina🇫🇷 · Florian Lyonnet🇺🇸 · Fredrick I. Olness🇺🇸 · Ingo Schienbein🇫🇷

    Searches for new physics will increasingly depend on identifying deviations from precision Standard Model (SM) predictions. Quantum Chromodynamics (QCD) will necessarily play a central role in this endeavor as it provides the framework for the parton model. However, as we move to higher orders and into extreme kinematic regions, we begin to see the full complexities of the QCD theory. Recent theoretical developments improve our ability to analyze both proton and nuclear PDFs across the full kinematic range. These developments are incorporated into the new nCTEQ15 PDFs, and we review these developments with respect to future measurements, and identify areas where additional effort is required.

    hep-phEPJ Web Conf.(2016)·0 citations
14. 14*

    Dark matter subhalos and unidentified sources in the Fermi 3FGL source catalog

    Djoeke Schoonenberg🇳🇱 · Jennifer Gaskins🇳🇱 · Gianfranco Bertone🇳🇱 · Jürg Diemand🇨🇭

    If dark matter consists of weakly interacting massive particles (WIMPs), dark matter subhalos in the Milky Way could be detectable as gamma-ray point sources due to WIMP annihilation. In this work, we perform an updated study of the detectability of dark matter subhalos as gamma-ray sources with the Fermi Large Area Telescope (Fermi LAT). We use the results of the Via Lactea II simulation, scaled to the Planck 2015 cosmological parameters, to predict the local dark matter subhalo distribution. Under optimistic assumptions for the WIMP parameters --- a 40 GeV particle annihilating to $b\bar{b}$ with a thermal cross-section, as required to explain the Galactic center GeV excess --- we predict that at most $\sim 10$ subhalos might be present in the third Fermi LAT source catalog (3FGL). This is a smaller number than has been predicted by prior studies, and we discuss the origin of this difference. We also compare our predictions for the detectability of subhalos with the number of subhalo candidate sources in 3FGL, and derive upper limits on the WIMP annihilation cross-section as a function of the particle mass. If a dark matter interpretation could be excluded for all 3FGL sources, our constraints would be competitive with those found by indirect searches using other targets, such as known Milky Way satellite galaxies.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAhep-phJCAP(2016)·50 citations
15. 15*

    On the R-Process Enrichment of Dwarf Spheroidal Galaxies

    Joseph Bramante🇺🇸 · Tim Linden🇺🇸

    Recent observations of Reticulum II have uncovered an overabundance of r-process elements, compared to similar ultra-faint dwarf spheroidal galaxies (UFDs). Because the metallicity and star formation history of Reticulum II appear consistent with all known UFDs, the high r-process abundance of Reticulum II suggests enrichment through a single, rare event, such as a double neutron star (NS) merger. However, we note that this scenario is extremely unlikely, as binary stellar evolution models require significant supernova natal kicks to produce NS-NS or NS-black hole mergers, and these kicks would efficiently remove compact binary systems from the weak gravitational potentials of UFDs. We examine alternative mechanisms for the production of r-process elements in UFDs, including a novel mechanism wherein NSs in regions of high dark matter density implode after accumulating a black-hole-forming mass of dark matter. We find that r-process proto-material ejection by tidal forces, when a single neutron star implodes into a black hole, can occur at a rate matching the r-process abundance of both Reticulum II and the Milky Way. Remarkably, dark matter models which collapse a single neutron star in observed UFDs also solve the missing pulsar problem in the Milky Way Galactic center. We propose tests specific to dark matter r-process production which may uncover, or rule out, this model.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAastro-ph.SR+1ApJ(2016)·37 citations
16. 16*

    Light-by-light scattering in ultraperipheral PbPb collisions at the Large Hadron Collider

    Mariola Klusek-Gawenda🇵🇱 · Piotr Lebiedowicz🇵🇱 · Antoni Szczurek🇵🇱

    We calculate cross sections for diphoton production in (semi)exclusive $PbPb$ collisions, relevant for the LHC. The calculation is based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $\gamma \gamma \to \gamma \gamma$ subprocess are calculated including two different mechanisms. We take into account box diagrams with leptons and quarks in the loops. In addition, we consider a vector-meson dominance (VDM-Regge) contribution with virtual intermediate hadronic (vector-like) excitations of the photons. We get much higher cross sections in $PbPb$ collisions than in earlier calculation from the literature. This opens a possibility to study the $\gamma \gamma \to \gamma \gamma$ (quasi)elastic scattering at the LHC. We present many interesting differential distributions which could be measured by the ALICE, CMS or ATLAS Collaborations at the LHC. We study whether a separation or identification of different components (boxes, VDM-Regge) is possible. We find that the cross section for elastic $\gamma \gamma$ scattering could be measured in the heavy-ion collisions for subprocess energies smaller than $W_{\gamma \gamma }\approx 15-20$ GeV.

    ↳ nucl-thhep-exhep-phPRC(2016)·119 citations
17. 17*

    Measurement of elliptic flow of light nuclei at $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV at RHIC

    STAR Collaboration: L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · A. Aparin · D. Arkhipkin · E. C. Aschenauer · M. U. Ashraf · A. Attri · G. S. Averichev and 327 other authors

    We present measurements of 2${}^{nd}$ order azimuthal anisotropy ($v_2$) at mid-rapidity $(|y|<1.0)$ for light nuclei d, t, ${}^3$He (for $\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and anti-nuclei $\bar{\mathrm{d}}$ ($\sqrt{s_{NN}}$ = 200, 62.4, 39, 27, and 19.6 GeV) and ${}^3\overline{\mathrm{He}}$ ($\sqrt{s_{NN}}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The $v_2$ for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{\mathrm{p}}$. We observe mass ordering in nuclei $v_2(p_T)$ at low transverse momenta ($p_T<2.0$ GeV/$c$). We also find a centrality dependence of $v_2$ for d and $\bar{\mathrm{d}}$. The magnitude of $v_2$ for t and ${}^3$He agree within statistical errors. Light-nuclei $v_2$ are compared with predictions from a blast wave model. Atomic mass number ($A$) scaling of light-nuclei $v_2(p_T)$ seems to hold for $p_T/A<1.5$ GeV/$c$. Results on light-nuclei $v_2$ from a transport-plus-coalescence model are consistent with the experimental measurements.

    ↳ nucl-exhep-exhep-phPRC(2016)·108 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.