Wed·Jul 22, 2015Wednesday·July 22, 2015

1. 01*

   Gravitino Dark Matter and low-scale Baryogenesis

   Giorgio Arcadi🇫🇷 · Laura Covi🇩🇪 · Marco Nardecchia🇬🇧

   A very simple way to obtain comparable baryon and DM densities in the early Universe is through their contemporary production from the out-of-equilibrium decay of a mother particle, if both populations are suppressed by comparably small numbers, i.e. the CP violation in the decay and the branching fraction respectively. We present a detailed study of this kind of scenario in the context of a R-parity violating realization of the MSSM in which the baryon asymmetry and the gravitino Dark Matter are produced by the decay of a Bino. The implementation of this simple picture in a realistic particle framework results, however, quite involving, due to the non trivial determination of the abundance of the decaying Bino, as well as due to the impact of wash-out processes and of additional sources both for the baryon asymmetry and the DM relic density. In order to achieve a quantitative determination of the baryon and Dark Matter abundances, we have implemented and solved a system of coupled Boltzmann equations for the particle species involved in their generation, including all the relevant processes. In the most simple, but still general, limit, in which the processes determining the abundance and the decay rate of the Bino are mediated by degenerate right-handed squarks, the correct values of the DM and baryon relic densities are achieved for a Bino mass between 50 and 100 TeV, Gluino NLSP mass in the range 15-60 TeV and a gravitino mass between 100 GeV and few TeV. These high masses are unfortunately beyond the kinematical reach of LHC. On the contrary, an antiproton signal from the decays of the gravitino LSP might be within the sensitivity of AMS-02 and gamma-ray telescopes.

   hep-phPRD(2015)·37 citations
2. 02*

   Hydrodynamical Description of the QCD Dirac Spectrum at Finite Chemical Potential

   Yizhuang Liu🇺🇸 · Piotr Warchol🇵🇱 · Ismail Zahed🇺🇸

   We present a hydrodynamical description of the QCD Dirac spectrum at finite chemical potential as an uncompressible droplet in the complex eigenvalue space. For a large droplet, the fluctuation spectrum around the hydrostatic solution is gapped by a longitudinal Coulomb plasmon, and exhibits a frictionless odd viscosity. The stochastic relaxation time for the restoration/breaking of chiral symmetry is set by twice the plasmon frequency. The leading droplet size correction to the relaxation time is fixed by a universal odd viscosity to density ratio ${\eta }_O/{\rho }_0=(\beta -2)/4$ for the three Dyson ensembles $\beta =1,2,4$.

   hep-phhep-lathep-thPRD(2015)·3 citations
3. 03*

   Interpretation of Vector-like Quark Searches: Heavy Gluons in Composite Higgs Models

   Juan Pedro Araque🇵🇹 · Nuno Filipe Castro🇵🇹 · Jose Santiago🇪🇸

   Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. We pay special attention to the sensitivity of the Large Hadron Collider experiments, both in run-1 and early run-2, to differences in the kinematical distributions from the different production mechanisms. We have found that even though there can be significant differences in some kinematical distributions at the parton level, the differences are washed out at the reconstruction level. Thus, the published experimental results can be reinterpreted in models with heavy gluons by simply rescaling the production cross section.

   hep-phhep-exJHEP(2015)·36 citations
4. 04*

   Associated production of a top-quark pair with vector bosons at NLO in QCD: impact on $t\bar{t}H$ searches at the LHC

   Fabio Maltoni🇧🇪 · Davide Pagani🇧🇪 · Ioannis Tsinikos🇧🇪

   We study the production of a top-quark pair in association with one and two vector bosons, $t\bar{t}V$ and $t\bar{t}VV$ with $V=\gamma ,Z,W^{\pm }$, at the LHC. We provide predictions at next-to-leading order in QCD for total cross sections and top-quark charge asymmetries as well as for differential distributions. A thorough discussion of the residual theoretical uncertainties related to missing higher orders and to parton distribution functions is presented. As an application, we calculate the total cross sections for this class of processes (together with $t\bar{t}H$ and $t\bar{t}t\bar{t}$ production) at hadron colliders for energies up to 100 TeV. In addition, by matching the NLO calculation to a parton shower, we determine the contribution of $t\bar{t}V$ and $t\bar{t}VV$ to final state signatures (two-photon and two-same-sign-, three- and four-lepton) relevant for $t\bar{t}H$ analyses at the Run II of the LHC.

   hep-phhep-exJHEP(2016)·181 citations
5. 05*

   Higgs Couplings in an Effective Theory Framework

   Hermes Belusca-Maito (Laboratoire de Physique Théorique, Université Paris-Sud XI, Orsay, France)🇫🇷

   The study of the properties of the scalar boson recently discovered at the LHC (ATLAS and CMS experiments) may allow us to know whether it is well described by the Standard Model. In the case where deviations from SM predictions are present, this would be an evidence for the presence of new physics. We focus on the study of the Higgs couplings to matter in a model-independent approach by introducing a dimension-6 effective Lagrangian that includes both CP-even and CP-odd effective couplings. Constraints are set on some of these coefficients using experimental data from ATLAS and CMS as well as electroweak precision measurements from LEP, SLC and Tevatron. These data meaningfully constrain CP-even and some CP-odd couplings.

   hep-ph7 citations
6. 06*

   Sterile Neutrino Dark Matter Production in the Neutrino-phillic Two Higgs Doublet Model

   Adisorn Adulpravitchai🇹🇭 · Michael A. Schmidt🇦🇺

   Sterile Neutrinos with a mass in the keV range form a good candidate for dark matter. They are naturally produced from neutrino oscillations via their mixing with the active neutrinos. However the production via non-resonant neutrino oscillations has recently been ruled out. The alternative production via Higgs decay is negligibly small compared to neutrino oscillations. We show that in the neutrino-phillic two Higgs doublet model, the contribution from Higgs decay can dominate over the contribution from neutrino oscillations and evade all constraints. We also study the free-streaming horizon and find that a sterile neutrino mass in the range of 4 to 53 keV leads to warm dark matter.

   hep-phastro-ph.COJHEP(2015)·28 citations
7. 07*

   Higgs boson cosmology

   Ian G. Moss🇬🇧

   The discovery of the Standard Model Higgs boson opens up a range of speculative cosmological scenarios, from the formation of structure in the early universe immediately after the big bang, to relics from the electroweak phase transition one nanosecond after the big bang, on to the end of the present-day universe through vacuum decay. Higgs physics is wide-ranging, and gives an impetus to go beyond the Standard Models of particle physics and cosmology to explore the physics of ultra-high energies and quantum gravity.

   hep-phastro-ph.COhep-thContemp.Phys.(2015)·8 citations
8. 08*

   Mini-Proceedings, 17th meeting of the Working Group on Radiative Corrections and MC Generators for Low Energies

   H. Czyż (ed.)🇵🇱 · S. Eidelman🇷🇺 · A. Hafner · C.F. Redmer🇸🇪 · P.A. Lukin🇷🇺 · T. Ferber🇩🇪 · P. Masjuan (ed.)🇩🇪 · K. Kołodziej🇵🇱 · O. Shekhovtsova🇵🇱 · G. Venanzoni (ed.)🇮🇹

   The mini-proceedings of the 17${}^{\mathrm{th}}$ Meeting of the "Working Group on Radiative Corrections and MonteCarlo Generators for Low Energies" held in Frascati, 20${}^{\mathrm{th}}$ - 21${}^{\mathrm{st}}$ April, are presented. These meetings, started in 2006, have as aim to bring together experimentalists and theoreticians working in the fields of meson transition form factors, hadronic contributions to the anomalous magnetic moment of the leptons, and the effective fine structure constant. The development of MonteCarlo generators and Radiative Corrections for precision $e^{+}{e}^{-}$ and $\tau$-lepton physics are also covered, with emphasis on meson production. Heavy quark masses were covered as well in this edition.

   hep-ph1 citation
9. 09*

   Single bottom quark production in kT-factorisation

   Grigorios Chachamis🇪🇸 · Michal Deak🇪🇸 · Martin Hentschinski🇲🇽 · German Rodrigo🇪🇸 · Agustin Sabio Vera🇪🇸

   We present a study within the kT-factorisation scheme on single bottom quark production at the LHC. In particular, we calculate the rapidity and transverse momentum differential distributions for single bottom quark/anti-quark production. In our setup, the unintegrated gluon density is obtained from the NLx BFKL Green function whereas we included mass effects to the Lx heavy quark jet vertex. We compare our results to the corresponding distributions predicted by the usual collinear factorisation scheme. The latter were produced with Pythia 8.1.

   hep-phJHEP(2015)·48 citations
10. 10*

    Survival of charged rho condensation at high temperature and density

    Hao Liu🇨🇳 · Lang Yu🇨🇳 · Mei Huang🇨🇳

    The charged vector $\rho$ mesons in the presence of external magnetic fields at finite temperature $T$ and chemical potential $\mu$ have been investigated in the framework of the Nambu--Jona-Lasinio model. We compute the masses of charged $\rho$ mesons numerically as a function of the magnetic field for different values of temperature and chemical potential. The self-energy of the $\rho$ meson contains the quark-loop contribution, i.e. the leading order contribution in $1/N_c$ expansion. The charged $\rho$ meson mass decreases with the magnetic field and drops to zero at a critical magnetic field $e{B}_c$, which means that the charged vector meson condensation, i.e. the electromagnetic superconductor can be induced above the critical magnetic field. Surprisingly, it is found that the charged $\rho$ condensation can even survive at high temperature and density. At zero temperature, the critical magnetic field just increases slightly with the chemical potential, which indicates that the charged $\rho$ condensation might occur inside compact stars. At zero density, in the temperature range $0.2-0.5\mathrm{GeV}$, the critical magnetic field for charged $\rho$ condensation is in the range of $0.2-0.6{\mathrm{GeV}}^2$, which indicates that the high temperature electromagnetic superconductor could be created at LHC.

    hep-phnucl-thCPC(2016)·21 citations
11. 11*

    Generalised Parton Distributions: A Dyson-Schwinger approach for the pion

    C. Mezrag🇫🇷

    We compute the pion quark Generalised Parton Distribution H and quark Double Distributions in a coupled Bethe-Salpeter and Dyson-Schwinger approach in terms of quark flavors or isospin states. We use analytic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We obtain an analytic expression for the pion Generalised Parton Distribution at a low scale. Our model fulfils most of the required symmetry properties and compares very well to experimental pion form factor or valence parton distribution function experimental data. In addition, we have highlighted limitations of the so-called impulse approximation, which breaks symmetries when computing the valence parton distribution function. Doing so, we introduced new terms which were neglected before. Finally, we also shed light on a specific property of the pion GPD: Polyakov soft pion theorem.

    hep-phnucl-thPoS(2015)·0 citations
12. 12*

    Nucleon Electric Dipole Moments in High-Scale Supersymmetric Models

    Junji Hisano🇯🇵 · Daiki Kobayashi🇯🇵 · Wataru Kuramoto🇯🇵 · Takumi Kuwahara🇯🇵

    The electric dipole moments (EDMs) of electron and nucleons are promising probes of the new physics. In generic high-scale supersymmetric (SUSY) scenarios such as models based on mixture of the anomaly and gauge mediations, gluino has an additional contribution to the nucleon EDMs. In this paper, we studied the effect of the $CP$-violating gluon Weinberg operator induced by the gluino chromoelectric dipole moment in the high-scale SUSY scenarios, and we evaluated the nucleon and electron EDMs in the scenarios. We found that in the generic high-scale SUSY models, the nucleon EDMs may receive the sizable contribution from the Weinberg operator. Thus, it is important to compare the nucleon EDMs with the electron one in order to discriminate among the high-scale SUSY models.

    hep-phJHEP(2015)·25 citations
13. 13*

    Configuration mixing and effective baryon-baryon interactions

    Xinmei Zhu🇨🇳 · Hongxia Huang🇨🇳 · Jialun Ping🇨🇳 · Fan Wang🇨🇳

    The effective baryon-baryon interactions is studied in the refined quark delocalization color screening model (QDCSM), in which the different quark clusterings are fully taken into account, instead of controlling by a variational delocalization parameter $ϵ(s)$ between two 3-quark clusters. The symmetry bases are employed to do the calculation, all possible configurations for two quark clusters are considered. The results obtained are very similar to that of QDCSM. It is inferred that the delocalization parameter $ϵ(s)$ used in QDCSM is an economic and effective way to describe the mixing of quarks between baryons.

    hep-phPRC(2015)·7 citations
14. 14*

    The Pentaquark Candidates in the Dynamical Diquark Picture

    Richard F. Lebed🇺🇸

    Starting with the dynamical picture of the exotic $c\bar{c}$-containing states $XYZ$ as the confinement-induced hadronization of a rapidly separating pair of a compact diquark and antidiquark, we describe the pentaquark candidates $P_c^{+}(4380)$ and $P_c^{+}(4450)$ in terms of a confined but rapidly separating color-antitriplet diquark $cu$ and color-triplet "triquark" $\bar{c}(ud)$. This separation explains the relatively small $P_c^{+}$ widths, despite these 5-quark systems lying far above both the $J/\psi p$ and ${\Lambda }_c{\bar{D}}^{(\ast )0}$ thresholds. The $P_c^{+}$ states are predicted to form isospin doublets with neutral partners $P_c^0$.

    hep-phnucl-thPLB(2015)·291 citations
15. 15*

    Separating Dijet Resonances Using the Color Discriminant Variable

    Elizabeth H. Simmons🇺🇸 · R. Sekhar Chivukula🇺🇸 · Pawin Ittisamai🇺🇸 · Natascia Vignaroli🇺🇸

    Color-singlet and color-octet vector bosons predicted in theories beyond the Standard Model have the potential to be discovered as dijet resonances at the LHC. A color-singlet resonance that has leptophobic couplings needs further investigation to be distinguished from a color-octet one. In previous work, we introduced a method for discriminating between the two kinds of resonances when their couplings are flavor-universal, using measurements of the dijet resonance mass, total decay width and production cross-section. Here, we describe two extensions of that work. First, we broaden the method to the case where the vector resonances have flavor non-universal couplings, by incorporating measurements of the heavy-flavor decays of the resonance. Second, we apply the method to separating vector bosons from color-octet scalars and excited quarks.

    hep-phhep-exInt.J.Mod.Phys.A(2017)·1 citation
16. 16*

    Constraints on $\mu$-distortion fluctuations and primordial non-Gaussianity from Planck data

    Rishi Khatri🇩🇪 · Rashid Sunyaev🇩🇪

    We use the Planck HFI channel maps to make an all sky map of $\mu$-distortion fluctuations. Our $\mu$-type distortion map is dominated by the $y$-type distortion contamination from the hot gas in the low redshift Universe and we can thus only place upper limits on the $\mu$-type distortion fluctuations. For the amplitude of $\mu$-type distortions on $10^{\prime }$ scales we get the limit on root mean square (rms) value ${\mu }_{rms}^{10^{\prime }}<6.4\times 10^{-6}$, a limit 14 times stronger than the COBE-FIRAS ($95\%$ confidence) limit on the mean of $<\mu ><90\times 10^{-6}$. Using our maps we also place strong upper limits on the auto angular power spectrum of $\mu$, $C_{\ell }^{\mu \mu }$ and the cross angular power spectrum of $\mu$ with the CMB temperature anisotropies, $C_{\ell }^{\mu T}$. The strongest observational limits are on the largest scales, $\ell (\ell +1)/(2\pi )C_{\ell }^{\mu \mu }{|}_{\ell =2-26}<(2.3\pm 1.0)\times 10^{-12}$ and $\ell (\ell +1)/(2\pi )C_{\ell }^{\mu T}{|}_{\ell =2-26}<(2.6\pm 2.6)\times 10^{-12}K$. Our observational limits can be used to constrain new physics which can create spatially varying energy release in the early Universe between redshifts $5\times 10^4\lesssim z\lesssim 2\times 10^6$. We specifically apply our observational results to constrain the primordial non-Gaussianity of the local type, when the source of $\mu$-distortion is Silk damping, for very squeezed configurations with the wavenumber for the short wavelength mode $46\lesssim k_S\lesssim 10^{4}Mp{c}^{-1}$ and for the long wavelength mode $k_L\approx 10^{-3}Mp{c}^{-1}$. Our limits on the primordial non-Gaussianity parameters are $f_{NL}<10^5,{\tau }_{NL}<1.4\times 10^{11}$ for $k_S/k_L\approx 5\times 10^4-10^7$. We give a new derivation of the evolution of the $\mu$-distortion fluctuations. We also introduce mixing of Bose-Einstein spectra and $y^{BE}$-type distortions.

    ↳ astro-ph.COhep-phJCAP(2015)·39 citations
17. 17*

    Searching for features of a string-inspired inflationary model with cosmological observations

    Yi-Fu Cai🇨🇦 · Elisa G. M. Ferreira🇨🇦 · Bin Hu🇳🇱 · Jerome Quintin🇨🇦

    The latest Planck results show a power deficit in the temperature anisotropies near $\ell \approx 20$ in the cosmic microwave background (CMB). This observation can hardly be explained within the standard inflationary $\Lambda$-cold-dark-matter ($\Lambda$CDM) scenario. In this paper we consider a string theory inspired inflationary model (axion monodromy inflation) with a step-like modulation in the potential which gives rise to observable signatures in the primordial perturbations. One interesting phenomenon is that the primordial scalar modes experience a sudden suppression at a critical scale when the modulation occurs. By fitting to the CMB data, we find that the model can nicely explain the $\ell \approx 20$ power deficit anomaly as well as predict specific patterns in the temperature-polarization correlation and polarization autocorrelation spectra. Though the significance of the result is not sufficient to claim a detection, our analysis reveals that fundamental physics at extremely high energy scales, namely, some effects inspired by string theory, may be observationally testable in forthcoming cosmological experiments.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2015)·34 citations
18. 18*

    Cost-Benefit Analysis of the Large Hadron Collider to 2025 and beyond

    Massimo Florio🇮🇹 · Stefano Forte🇮🇹 · Emanuela Sirtori🇮🇹

    Social cost-benefit analysis (CBA) of projects has been successfully applied in different fields such as transport, energy, health, education, and environment, including climate change. It is often argued that it is impossible to extend the CBA approach to the evaluation of the social impact of research infrastructures, because the final benefit to society of scientific discovery is generally unpredictable. Here, we propose a quantitative approach to this problem, we use it to design an empirically testable CBA model, and we apply it to the the Large Hadron Collider (LHC), the highest-energy accelerator in the world, currently operating at CERN. We show that the evaluation of benefits can be made quantitative by determining their value to users (scientists, early-stage researchers, firms, visitors) and non-users (the general public). Four classes of contributions to users are identified: knowledge output, human capital development, technological spillovers, and cultural effects. Benefits for non-users can be estimated, in analogy to public goods with no practical use (such as environment preservation), using willingness to pay. We determine the probability distribution of cost and benefits for the LHC since 1993 until planned decommissioning in 2025, and we find there is a 92% probability that benefits exceed its costs, with an expected net present value of about 3 billion euro, not including the unpredictable economic value of discovery of any new physics. We argue that the evaluation approach proposed here can be replicated for any large-scale research infrastructure, thus helping the decision-making on competing projects, with a socio-economic appraisal complementary to other evaluation criteria.

    ↳ physics.soc-phhep-exhep-phhep-th+17 citations
19. 19*

    Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from $t\bar{t}$ production at the Tevatron

    D0 Collaboration

    We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in $t\bar{t}$ production in dilepton final states using 9.7 fb${}^{-1}$ of proton-antiproton collisions at $\sqrt{s}=1.96$ TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible $t\bar{t}$ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of $A^{t\bar{t}}=(15.0\pm 6.4\text{ (stat)}\pm 4.9\text{ (syst)})\%$ and a top-quark polarization times spin analyzing power in the beam basis of $\kappa P=(7.2\pm 10.5\text{ (stat)}\pm 4.2\text{ (syst)})\%$, with a correlation of $-56\%$ between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of $\kappa P=(11.3\pm 9.1\text{ (stat)}\pm 1.9\text{ (syst)})\%.$ If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of $A^{t\bar{t}}=(17.5\pm 5.6\text{ (stat)}\pm 3.1\text{ (syst)})\%.$ A combination with the D0 $A^{t\bar{t}}$ measurement in the lepton+jets final state yields an asymmetry of $A^{t\bar{t}}=(11.8\pm 2.5\text{ (stat)}\pm 1.3\text{ (syst)})\%.$ Within their respective uncertainties, all these results are consistent with the standard model expectations.

    ↳ hep-exhep-phPRD(2015)·47 citations
20. 20*

    The road to MOND--a novel perspective

    Mordehai Milgrom🇮🇱

    Accepting that galactic mass discrepancies are due to modified dynamics, I show why it is specifically the MOND paradigm that is pointed to cogently. MOND is thus discussed here as a special case of a larger class of modified dynamics theories whereby galactic systems with large mass discrepancies are described by scale-invariant dynamics. This is a novel presentation that uses more recent, after-the-fact insights and data (largely predicted beforehand by MOND). Starting from a purist set of tenets, I follow the path that leads specifically to the MOND basic tenets. The main signposts are: (i) Space-time scale invariance underlies the dynamics of systems with large mass discrepancies. (ii) In these dynamics, $G$ must be replaced by a single "scale-invariant" gravitational constant, Q0 (in MOND, Q0=A0=Ga0, where a0 is MOND's acceleration constant). (iii) Universality of free fall points to the constant q0=Q0/G as the boundary between the G-controlled, standard dynamics, and the Q0-controlled, scale-invariant dynamics (in MOND, q0=a0). (iv) Data clinches the case for q0 being an acceleration (MOND).

    ↳ astro-ph.GAastro-ph.COgr-qchep-phPRD(2015)·16 citations
21. 21*

    Bose-Einstein condensates in neutron stars

    C.J. Pethick🇩🇰 · Thomas Schaefer🇺🇸 · A. Schwenk🇩🇪

    In the two decades since the appearance of the book "Bose-Einstein Condensation" in 1995, there have been a number of developments in our understanding of dense matter. After a brief overview of neutron star structure and the Bose-Einstein condensed phases that have been proposed, we describe selected topics, including neutron and proton pairing gaps, the physics of the inner crust of neutron stars, where a neutron fluid penetrates a lattice of nuclei, meson condensates, and pairing in dense quark matter. Especial emphasis is placed on basic physical effects and on connections to the physics of cold atomic gases.

    ↳ nucl-thastro-ph.HEcond-mat.quant-gashep-ph23 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.