Wed·Mar 7, 2018Wednesday·March 7, 2018

1. 01*

   The Light Gluino Gap

   Jared A. Evans🇺🇸 · David McKeen🇺🇸

   A variety of experimental searches and theoretical efforts have constrained gluinos that undergo an all-hadronic decay with no missing energy, as can arise in R-parity violating or stealth supersymmetry. Although the gluino->jj decay is robustly excluded, there is gap in current experimental coverage for gluinos with masses between 51-76 GeV that decay into three light-flavor quarks. In this work, we probe this gap with published multi-jet data from the UA2 experiment. Despite setting the strongest current limit on this region, we find that UA2 data is unable to close this gap for gluino->jjj decays. In addition to this three-jet gap, we note an additional gap for all-hadronic gluino -> n parton decays with $n\ge 4$ for light gluinos (51 GeV < m < 300 GeV) not covered by the current search program.

   hep-ph6 citations
2. 02*

   Matter effects on the flavor conversions of solar neutrinos and high-energy astrophysical neutrinos

   Guo-yuan Huang🇨🇳 · Jun-Hao Liu🇨🇳 · Shun Zhou🇨🇳

   Can we observe the solar eclipses in the neutrino light? In principle, this is possible by identifying the lunar matter effects on the flavor conversions of solar neutrinos when they traverse the Moon before reaching the detectors at the Earth. Unfortunately, we show that the lunar matter effects on the survival probability of solar ${}^8\mathrm{B}$ neutrinos are suppressed by an additional factor of $1.2\%$, compared to the day-night asymmetry. However, we point out that the matter effects on the flavor conversions of high-energy astrophysical neutrinos, when they propagate through the Sun, can be significant. Though the flavor composition of high-energy neutrinos can be remarkably modified, it is quite challenging to observe such effects even in the next-generation of neutrino telescopes.

   hep-phNPB(2018)·9 citations
3. 03*

   Nearly isentropic flow at sizeable $\eta /s$

   Aleksi Kurkela🇨🇭 · Urs Achim Wiedemann🇨🇭 · Bin Wu🇨🇭

   Non-linearities in the harmonic spectra of hadron-nucleus and nucleus-nucleus collisions provide evidence for the dynamical response to azimuthal spatial eccentricities. Here, we demonstrate within the framework of transport theory that even the mildest interaction correction to a picture of free-streaming particle distributions, namely the inclusion of one perturbatively weak interaction ("one-hit dynamics"), will generically give rise to all observed linear and non-linear structures. We further argue that transport theory naturally accounts within the range of its validity for realistic signal sizes of the linear and non-linear response coefficients observed in azimuthal momentum anisotropies with a large mean free path of the order of the system size in peripheral ($\sim 50\%$ centrality) PbPb or central pPb collisions. The shear viscosity to entropy density ratio $\eta /s$ of such a transport theory is approximately an order of magnitude larger than that of an almost perfect fluid. The phenomenological success of transport simulations thus challenges the perfect fluid paradigm of ultra-relativistic nucleus-nucleus and hadron-nucleus collisions.

   hep-phhep-exnucl-exnucl-thPLB(2018)·67 citations
4. 04*

   Semileptonic ${\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell }$ Transition in Full QCD

   K. Azizi🇹🇷 · J. Y. Sungu🇹🇷

   The tree-level $b\to c\ell {\bar{\nu }}_{\ell }$ based hadronic transitions have been on the focus of much attention since recording significant deviations of the experimental data, on the ratios of the branching fractions in $\tau$ and $e-\mu$ channels of the semileptonic $B\to D$ transition, from the SM predictions by BaBar Collaboration in 2012. It can be of great importance to look whether similar discrepancies take place in the semileptonic baryonic ${\Lambda }_b\to {\Lambda }_c\ell {\bar{\nu }}_{\ell }$ decay channel or not. In this accordance we estimate the decay width as well as the ratios of the branching fractions in $\tau$ and $e-\mu$ channels of this baryonic transition by calculating the form factors, entering the amplitude of this transition as the main inputs, in the framework of QCD sum rules in full theory. We compare the obtained results with the predictions of other theoretical studies. Our results may be compared with the corresponding future experimental data to look for possible deviations of data from the SM predictions.

   hep-phhep-exhep-latPRD(2018)·45 citations
5. 05*

   Spectroscopy of ${\Omega }_{ccb}$ baryon in Hypercentral Quark Model

   Zalak Shah🇮🇳 · Ajay Kumar Rai🇮🇳

   We extract the mass spectra of triply heavy baryon ${\Omega }_{ccb}$ using Hypercentral constituent quark model. The first order correction is also added to the potential term of Hamiltonian. The radial and orbital excited state masses are also determined. Moreover, the Regge trajectories and magnetic moments are also given for this baryon.

   hep-phCPC(2018)·31 citations
6. 06*

   Dark Matter Direct Detection from new interactions in models with spin-two mediators

   A. Carrillo-Monteverde🇬🇧 · Yoo-Jin Kang🇰🇷 · Hyun Min Lee🇰🇷 · Myeonghun Park🇰🇷 · Veronica Sanz🇬🇧

   We consider models where a massive spin-two resonance acts as the mediator between Dark Matter (DM) and the SM particles through the energy-momentum tensor. We examine the effective theory for fermion, vector and scalar DM generated in these models and find novel types of DM-SM interaction never considered before. We identify the effective interactions between DM and the SM quarks when the mediator is integrated out, and match them to the gravitational form factors relevant for spin-independent DM-nucleon scattering. We also discuss the interplay between DM relic density conditions, direct detection bounds and collider searches for the spin-two mediator.

   hep-phJHEP(2018)·38 citations
7. 07*

   SModelS extension with the CMS supersymmetry search results from Run 2

   Juhi Dutta🇮🇳 · Sabine Kraml🇫🇷 · Andre Lessa🇧🇷 · Wolfgang Waltenberger🇦🇹

   We present the update of the SModelS database with the simplified model results from CMS searches for supersymmetry at Run 2 with 36 fb${}^{-1}$ of data. The constraining power of these new results is compared to that of the 8 TeV results within the context of a full model, the pMSSM. The new database, v1.1.2, is publicly available and can readily be employed for physics studies with SModelS.

   hep-phhep-exLHEP(2018)·54 citations
8. 08*

   Heavy neutral fermions at the high-luminosity LHC

   Juan Carlos Helo🇨🇱 · Martin Hirsch🇪🇸 · Zeren Simon Wang🇩🇪

   Long-lived light particles (LLLPs) appear in many extensions of the standard model. LLLPs are usually motivated by the observed small neutrino masses, by dark matter or both. Typical examples for fermionic LLLPs (a.k.a. heavy neutral fermions, HNFs) are sterile neutrinos or the lightest neutralino in R-parity violating supersymmetry. The high luminosity LHC is expected to deliver up to 3/ab of data. Searches for LLLPs in dedicated experiments at the LHC could then probe the parameter space of LLLP models with unprecedented sensitivity. Here, we compare the prospects of several recent experimental proposals, FASER, CODEX-b and MATHUSLA, to search for HNFs and discuss their relative merits.

   hep-phJHEP(2018)·124 citations
9. 09*

   An overview of ${\Lambda }_c$ decays

   Michael Gronau · Jonathan L. Rosner

   The decays of the ground-state charmed baryon ${\Lambda }_c$ are now close to being completely mapped out. In this paper we discuss some remaining open questions, whose answers can help shed light on weak processes contributing to those decays, on calculations of such quantities as transition form factors in lattice QCD, and on missing decay modes such as ${\Lambda }_c\to {\Lambda }^{\ast }{\ell }^{+}{\nu }_{\ell }$, where ${\Lambda }^{\ast }$ is an excited resonance. The discussion is in part a counterpart to a previous analysis of inclusive $D_s$ decays.

   hep-phhep-exPhys. Rev. D 97, 116015 (2018)
10. 10*

    Potential Energy Between Static Quarks Is Time Dependent in The Classical Yang-Mills Theory

    Gouranga C Nayak🇺🇸

    Lattice QCD predicts that the potential energy between static quarks is independent of time. However, in this paper we show that the gauge invariant color singlet potential energy between static quarks in the classical Yang-Mills theory depends on time even if the quarks are at rest. This is a consequence of the time dependent fundamental color charge $q^a(t)$ of the quark in the classical Yang-Mills theory. We find that the gauge invariant color singlet time dependent potential energy between static quarks does not violate the conservation of energy in the Yang-Mills theory.

    hep-phhep-latnucl-th3 citations
11. 11*

    Weak Decays of Heavy Baryons in Light-Front Approach

    Zhen-Xing Zhao🇨🇳

    In this work, we perform a analysis of semi-leptonic and nonleptonic weak decays of heavy baryons: ${\Lambda }_b,{\Xi }_b,{\Omega }_b$ and ${\Lambda }_c,{\Xi }_c,{\Omega }_c$. For nonleptonic decay modes, we study only the factorizable channels induced by the external W-emission. The two spectator quarks in baryonic transitions are treated as a diquark and form factors are calculated in the light-front approach. Using the results for form factors, we also calculate some corresponding semi-leptonic and nonleptonic decay widths. We find that our results are comparable with the available experimental data and other theoretical predictions. Decay branching fractions for many channels are found to reach the level $10^{-3}\sim 10^{-2}$, which are promising to be discovered in the future measurements at BESIII, LHCb and BelleII. The SU(3) symmetry in semi-leptonic decays is examined and sources of symmetry breaking are discussed.

    hep-phhep-exCPC(2018)·121 citations
12. 12*

    De-Confinement in high multiplicity proton-proton collisions at LHC energies

    A. S. Hirsch · C. Pajares · R. P. Scharenberg · B. K. Srivastava

    Recently, the CMS Collaboration has published identified particle transverse momentum spectra in high multiplicity events at LHC energies $\sqrt{s}$ = 0.9-13 TeV. In the present work the transverse momentum spectra have been analyzed in the framework of the color fields inside the clusters of overlapping strings, which are produced in high energy hadronic collisions. The non-Abelian nature is reflected in the coherence sum of the color fields which as a consequence gives rise to an enhancement of the transverse momentum and a suppression of the multiplicities relative to the non overlapping strings. The initial temperature and shear viscosity to entropy density ratio $\eta /s$ are obtained. For the higher multiplicity events at $\sqrt{s}$ =7 and 13 TeV the initial temperature is above the universal hadronization temperature and is consistent with the creation of de-confined matter. In these small systems it can be argued that the thermalization is a consequence of the quantum tunneling through the event horizon introduced by the confining color fields, in analogy to the Hawking-Unruh effect. The small shear viscosity to entropy density ratio $\eta /s$ near the critical temperature suggests that the matter is a strongly coupled Quark Gluon Plasma.

    hep-phhep-exPRD(2019)·47 citations
13. 13*

    Methods for separation of deuterons produced in the medium and in jets in high energy collisions

    Natasha Sharma🇮🇳 · Tony Perez🇺🇸 · Andy Castro🇺🇸 · Lokesh Kumar🇮🇳 · Christine Nattrass🇺🇸

    Coalescence has long been used to describe the production of light (anti-)nuclei in heavy ion collisions. The same underlying mechanism may also exist in jets when a proton and a neutron are close enough in phase space to form a deuteron. We model deuteron production in jets by applying an afterburner to protons and neutrons produced in PYTHIA for $p$+$p$ collisions at a center of mass energy $\sqrt{s}=$ 7 TeV. PYTHIA provides a reasonable description of the proton spectra and the shape of the deuteron spectrum predicted by the afterburner is in agreement with the data. We show that the rise in the coalescence parameter $B_2$ with momentum observed in data is consistent with coalescence in jets. We show that di-hadron correlations can be used to separate the contributions from the jet and the underlying event. This model predicts that the conditional coalescence parameter in the jet-like correlation should be independent of the trigger momentum.

    hep-phnucl-thPRC(2018)·13 citations
14. 14*

    Monte Carlo Top Quark Mass Calibration

    Bahman Dehnadi🇩🇪 · André H. Hoang🇦🇹 · Vicent Mateu🇪🇸 · Moritz Preisser🇦🇹 · Iain W. Stewart🇺🇸

    The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, $m_t^{\mathrm{MC}}$. Due to the complicated interplay of hadronization and parton shower dynamics in Monte Carlo event generators relevant for kinematic reconstruction, relating $m_t^{\mathrm{MC}}$ to field theory masses is a non-trivial task. In this talk we report on a calibration procedure to determine this relation using hadron level QCD predictions for 2-Jettiness in $e^{+}{e}^{-}$ annihilation, an observable which has kinematic top mass sensitivity and a close relation to the invariant mass of the particles coming from the top decay. The theoretical ingredients of the QCD prediction are reviewed. Fitting $e^{+}{e}^{-}$ 2-Jettiness calculations at NLL/NNLL order to PYTHIA 8.205, we find that $m_t^{\mathrm{MC}}$ agrees with the MSR mass $m_{t,1\mathrm{GeV}}^{\mathrm{MSR}}$ within uncertainties. At NNLL we find $m_t^{\mathrm{MC}}=m_{t,1\mathrm{GeV}}^{\mathrm{MSR}}+(0.18\pm 0.22)\mathrm{GeV}$. $m_t^{\mathrm{MC}}$ can differ from the pole mass $m_t^{\mathrm{pole}}$ by up to $600\mathrm{MeV}$, and using the pole mass generally leads to larger uncertainties. At NNLL we find $m_t^{\mathrm{MC}}=m_t^{\mathrm{pole}}+(0.57\pm 0.28)\mathrm{GeV}$ as the fit result. In contrast, converting $m_{t,1\mathrm{GeV}}^{\mathrm{MSR}}$ obtained at NNLL to the pole mass gives a result for $m_t^{\mathrm{pole}}$ that is substantially larger and incompatible with the fit result. We also explain some theoretical aspects relevant for employing the C-parameter as an alternative calibration observable.

    hep-phPoS(2018)·4 citations
15. 15*

    IceCube bounds on sterile neutrinos above 10 eV

    Mattias Blennow🇪🇸 · Enrique Fernandez-Martinez🇪🇸 · Julia Gehrlein🇪🇸 · Josu Hernandez-Garcia🇮🇹 · Jordi Salvado🇪🇸

    We study the capabilities of IceCube to search for sterile neutrinos with masses above 10 eV by analyzing its ${\nu }_{\mu }$ disappearance atmospheric neutrino sample. We find that IceCube is not only sensitive to the mixing of sterile neutrinos to muon neutrinos, but also to the more elusive mixing with tau neutrinos through matter effects. The currently released 1-year data shows a mild (around 2$\sigma$) preference for non-zero sterile mixing, which overlaps with the favoured region for the sterile neutrino interpretation of the ANITA upward shower. Although the null results from CHORUS and NOMAD on ${\nu }_{\mu }$ to ${\nu }_{\tau }$ oscillations in vacuum disfavour the hint from the IceCube 1-year data, the relevant oscillation channel and underlying physics are different. At the $99\%$ C.L. an upper bound is obtained instead that improves over the present Super-Kamiokande and DeepCore constraints in some parts of the parameter space. We also investigate the physics reach of the roughly 8 years of data that is already on tape as well as a forecast of 20 years data to probe the present hint or improve upon current constraints.

    hep-phEPJC(2018)·22 citations
16. 16*

    On the behaviour of composite resonances breaking lepton flavour universality

    Mikael Chala🇬🇧 · Michael Spannowsky🇬🇧

    Within the context of composite Higgs models, recent hints on lepton-flavour non-universality in $B$ decays can be explained by a vector resonance $V$ with sizeable couplings to the Standard Model leptons ($\ell$). We argue that, in such a case, spin-$1/2$ leptonic resonances ($L$) are most probably light enough to open the decay mode $V\to L\ell$. This implies, in combination with the fact that couplings between composite resonances are much larger than those between composite and elementary fields, that this new decay can be important. In this paper, we explore under which conditions it dominates over other decay modes. Its discovery, however, requires a dedicated search strategy. Employing jet substructure techniques, we analyse the final state with largest branching ratio, namely ${\mu }^{+}{\mu }^{-}Z/h,Z/h\to$ jets. We show that (i) parameter space regions that were believed excluded by di-muon searches are still allowed, (ii) these regions can already be tested with the dedicated search we propose and (iii) $V$ masses as large as $\sim 3.5$ TeV can be probed at the LHC during the high-luminosity phase.

    hep-phPRD(2018)·28 citations
17. 17*

    Soft evolution after a hard scattering process

    Duff Neill🇺🇸 · Varun Vaidya🇺🇸

    The dynamical cascade of momentum, spin, charge, and other quantum numbers from an ultra-violet process into the infra-red is a fundamental concern for asymptotically free or conformal gauge field theories. It is also a practical concern for any high energy scattering experiment with energies above tens of GeV. We present a formulation of the evolution equation that governs this cascade, the Banfi-Marchesini-Smye equation, from both an effective field theory point of view and a direct diagrammatic argument. The equation uses exact momentum conservation, and is applicable to both scattering with initial and final state hard partons. The direct diagrammatic formulation is organized by constructing a generating functional. This functional is also automatically realized with soft wilson lines and collinear field operators coupled to external currents. The two approaches are directly connected by reverse engineering the Lehman-Symanzik-Zimmermann reduction procedure to insert states within the soft and collinear matrix elements. At leading order, the cascade is completely controlled by the soft anomalous dimension. By decomposing the anomalous dimension into on-shell and off-shell regions as would be realized in the effective field theory approach with a Glauber mediating potential, we are forced to choose a transverse momentum ordering in order to trivialize the overlap between Glauber potential contributions and the pure soft region. The evolution equation then naturally incorporates factorization violating effects driven by off-shell exchanges for active partons. Finally, we examine the consequences of abandoning exact momentum conservation as well as terminating the evolution at the largest inclusive scale, procedures often used to simplify the analysis of the cascade.

    hep-phhep-th9 citations
18. 18*

    Analyzing the Gamma-ray Sky with Wavelets

    Bhaskaran Balaji🇺🇸 · Ilias Cholis🇺🇸 · Patrick J. Fox🇺🇸 · Samuel D. McDermott🇺🇸

    We analyze the gamma-ray sky at energies of 0.5 to 50 GeV using the undecimated wavelet transform on the sphere. Focusing on the inner $60^{\circ }\times 60^{\circ }$ of the sky, we identify and characterize four separate residuals beyond the expected Milky Way diffuse emission. We detect the \textit{Fermi} Bubbles, finding compelling evidence that they are diffuse in nature and contain very little small-scale structure. We detect the "cocoon" inside the Southern Bubble, and we also identify its northern counterpart above 2 GeV. The Northern Cocoon lies along the same axis but is $\sim 30\%$ dimmer than the southern one. We characterize the Galactic center excess, which we find extends up to $20^{\circ }$ in $|b|$. At latitudes $|b|\le 5^{\circ }$ we find evidence for power in small angular scales that could be the result of point-source contributions, but for $|b|\ge 5^{\circ }$ the Galactic center excess is dominantly diffuse in its nature. Our findings show that either the Galactic center excess and {\it Fermi} Bubbles connect smoothly or that the Bubbles brighten significantly below $15^{\circ }$ in latitude. We find that the Galactic center excess appears off-center by a few degrees towards negative $\ell$. Additionally, we find and characterize two emissions along the Galactic disk centered at $\ell \simeq +25^{\circ }$ and $-20^{\circ }$. These emissions are significantly more elongated along the Galactic disk than the Galactic center excess.

    ↳ astro-ph.HEastro-ph.COastro-ph.GAastro-ph.IM+1PRD(2018)·23 citations
19. 19*

    Beam energy dependence of squeeze-out effect on the directed and elliptic flow in Au+Au collisions at high baryon density region

    Chao Zhang🇨🇳 · Jiamin Chen🇨🇳 · Xiaofeng Luo🇨🇳 · Feng Liu🇨🇳 · Yasushi Nara🇯🇵

    We present a detailed analysis of the beam energy dependence of the mechanisms for the generation of directed and elliptic flows in Au+Au collisions focusing on the role of hadronic rescattering and spectator shadowing within a microscopic transport model JAM with different equation of state. A systematic study of the beam energy dependence is performed for Au+Au collisions at $\sqrt{s_{NN}}=2.3-62.4$ GeV. The transition of the dynamical origin of the directed flow is observed. We find that the initial Glauber type nucleon-nucleon collisions generate negative $v_1$ for nucleons at midrapidity due to the presence of spectator matter, and this negative nucleon $v_1$ is turned to be positive by the meson-baryon interactions at the beam energy region of $\sqrt{s_{NN}}<30$ GeV. In contrast, above 30 GeV there is no spectator shadowing at midrapidity, and initial nucleon-nucleon collisions do not generate directed flow, but subsequent rescatterings among produced particles generate negative $v_1$ for nucleons. It is demonstrated that negative pion-directed flows are mostly generated by the interaction with the spectator matter. It is also shown that the squeeze-out effect is largely suppressed in the case of softening, which leads to the enhancement of elliptic flow around $\sqrt{s_{NN}}=5-7$ GeV. The elliptic flow at midrapidity above 10 GeV is not influenced by the squeeze-out due to spectator matter, while its effect is seen at the forward rapidity range of $y/y_{c.m.}>0.5$, which decreases as beam energy increases.

    ↳ nucl-exhep-exhep-phnucl-thPRC(2018)·32 citations
20. 20*

    Revisit of cosmic ray antiprotons from dark matter annihilation with updated constraints on the background model from AMS-02 and collider data

    Ming-Yang Cui (NJU, PMO)🇨🇳 · Xu Pan (PMO)🇨🇳 · Qiang Yuan (PMO, USTC, PKU)🇨🇳 · Yi-Zhong Fan (PMO, USTC)🇨🇳 · Hong-Shi Zong (NJU)🇨🇳

    We study the cosmic ray antiprotons with updated constraints on the propagation, proton injection, and solar modulation parameters based on the newest AMS-02 data near the Earth and Voyager data in the local interstellar space, and on the cross section of antiproton production due to proton-proton collisions based on new collider data. We use a Bayesian approach to properly consider the uncertainties of the model predictions of both the background and the dark matter (DM) annihilation components of antiprotons. We find that including an extra component of antiprotons from the annihilation of DM particles into a pair of quarks can improve the fit to the AMS-02 antiproton data considerably. The favored mass of DM particles is about $60\sim 100$ GeV, and the annihilation cross section is just at the level of the thermal production of DM ($⟨\sigma v⟩\sim O(10^{-26})$ cm${}^3$~s${}^{-1}$).

    ↳ astro-ph.HEhep-phJCAP(2018)·47 citations
21. 21*

    Electric structure of shallow D-wave states in Halo EFT

    J. Braun🇩🇪 · W. Elkamhawy🇩🇪 · R. Roth🇩🇪 · H.-W. Hammer🇩🇪

    We compute the electric form factors of one-neutron halo nuclei with shallow D-wave states up to next-to-leading order and the E2 transition from the S-wave to the D-wave state up to leading order in Halo Effective Field Theory (Halo EFT). The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of $R_{core}/R_{halo}$, where $R_{core}$ and $R_{halo}$ denote the length scales of the core and the halo, respectively. We propose a power counting scenario for weakly-bound states in one-neutron Halo EFT and discuss its implications for higher partial waves in terms of universality. The scenario is applied to the ${\frac{5}{2}}^{+}$ first excited state and the ${\frac{1}{2}}^{+}$ ground state of ${}^{15}\text{C}$. We obtain several universal correlations between electric observables and use data for the E2 transition ${\frac{5}{2}}^{+}\to {\frac{1}{2}}^{+}$ together with ab initio results from the No-Core Shell Model to predict the quadrupole moment.

    ↳ nucl-thhep-phJ.Phys.G(2019)·11 citations
22. 22*

    Multifield Polygonal Bounces

    Victor Guada🇸🇮 · Alessio Maiezza🇭🇷 · Miha Nemevšek🇸🇮

    We propose a new approach for computing tunneling rates in quantum or thermal field theory with multiple scalar fields. It is based on exact analytical solutions of piecewise linear potentials with many segments that describes any given potential to arbitrary precision. The method is first developed for the single field case in 3 and 4 space-time dimensions and demonstrated on examples of classical potentials as well as the calculation of quantum fluctuations. A systematic expansion of the potential beyond the linear order is considered, taking into account higher order corrections, which paves the way for multiple scalar fields. We thereby provide a fast semi-analytical tool for evaluating the bounce action for theories with an extended scalar sector.

    ↳ hep-thgr-qchep-phPRD(2019)·44 citations
23. 23*

    High Precision Statistical Landau Gauge Lattice Gluon Propagator Computation vs. the Gribov-Zwanziger approach

    David Dudal🇧🇪 · Orlando Oliveira🇵🇹 · Paulo J. Silva🇵🇹

    The compatibility of the results from the Gribov-Zwanziger tree level prediction and lattice simulations, using large statistical ensembles, for the Landau gauge gluon propagator are investigated, thereby complementing earlier work using small-scale statistics. Our results show that the data is well described by the tree level estimate only up to momenta $p\lesssim 1$ GeV while clearly favoring the so-called Refined Gribov-Zwanziger scenario, implying particular relations between certain possible $d=2$ condensates. We also provide a global fit of the lattice data which interpolates between the above scenario at low momenta and the usual continuum one-loop renormalization improved perturbation theory after introducing an infrared log-regularizing term.

    ↳ hep-lathep-phhep-thnucl-thAnnals Phys.(2018)·81 citations
24. 24*

    The CMB neutrino mass / vacuum energy degeneracy: a simple derivation of the degeneracy slopes

    Will Sutherland🇬🇧

    It is well known that estimating cosmological parameters from cosmic microwave background (CMB) data alone results in a significant degeneracy between the total neutrino mass and several other cosmological parameters, especially the Hubble constant H_0 and the matter density parameter ${\Omega }_m$. Adding low-redshift measurements such as baryon acoustic oscillations (BAOs) breaks this degeneracy and greatly improves the constraints on neutrino mass. The sensitivity is surprisingly high, e.g. adding the $\sim 1$ percent measurement of the BAO ratio $r_s/D_V$ from the BOSS survey leads to a limit $\Sigma m_{\nu }<0.19$ eV, equivalent to ${\Omega }_{\nu }<0.0045$ at 95\% confidence. For the case of $\Sigma m_{\nu }<0.6$ eV, the CMB degeneracy with neutrino mass almost follows a track of constant sound horizon angle (Howlett et al 2012). For a $\Lambda$CDM + $m_{\nu }$ model, we use simple but quite accurate analytic approximations to derive the slope of this track, giving dimensionless multipliers between the neutrino to matter ratio ($x_{\nu }\equiv {\omega }_{\nu }/{\omega }_{cb}$) and the shifts in other cosmological parameters. The resulting multipliers are substantially larger than 1: conserving the CMB sound horizon angle requires parameter shifts $\delta \ln H_0\approx -2\delta x_{\nu }$, $\delta \ln {\Omega }_m\approx +5\delta x_{\nu }$, $\delta \ln {\omega }_{\Lambda }\approx -6.2\delta x_{\nu }$, and most notably $\delta {\omega }_{\Lambda }\approx -14\delta {\omega }_{\nu }$. These multipliers give an intuitive derivation of the degeneracy direction, which agrees well with the numerical likelihood results from the Planck team.

    ↳ astro-ph.COhep-phMNRAS(2018)·11 citations
25. 25*

    Time-dependent Features in the Primordial Spectrum

    Laura Covi🇩🇪 · Simone Dresti🇩🇪

    In a Quantum Field Theory with a time-dependent background, time-translational symmetry is broken. We therefore expect time-dependent loop corrections to cosmological observables after renormalization for an interacting field, with the consequent physical implications. In this paper we compute and discuss such radiative corrections to the primordial spectrum within simple models, both for massless and massive virtual fields, and we disentangle the time-dependence caused by the background and by the initial state after renormalization. For the investigated models the departure from near-scale-invariance is very small and there is full compatibility with the current Planck data constraints. Future CMB measurements may improve the current constraints on feature-full primordial spectra and possibly observe these effects in the most optimistic scenario of hybrid inflation, revealing the interacting nature of the inflaton field.

    ↳ gr-qchep-phhep-th3 citations
26. 26*

    Open charm and dileptons from relativistic heavy-ion collisions

    Taesoo Song🇩🇪 · Wolfgang Cassing🇩🇪 · Pierre Moreau🇩🇪 · Elena Bratkovskaya🇩🇪

    Dileptons are considered as one of the cleanest signals of the quark-gluon plasma (QGP), however, the QGP radiation is masked by many 'background' sources from either hadronic decays or semileptonic decays from correlated charm pairs. In this study we investigate the relative contribution of these channels in heavy-ion collisions from $\sqrt{s_{\mathrm{NN}}}=$ 8 GeV to 5 TeV with a focus on the competition between the thermal QGP radiation and the semileptonic decays from correlated $D-$meson pairs. As a 'tool' we employ the parton-hadron-string dynamics (PHSD) transport approach to study dilepton spectra in Pb+Pb (Au+Au) collisions in a wide energy range incorporating for the first time a fully microscopic treatment of the charm dynamics and their semileptonic decays. We find that the dileptons from correlated $D-$meson decays dominate the 'thermal' radiation from the QGP in central Pb+Pb collisions at the intermediate masses (1.2 GeV $<M<$ 3 GeV) for $\sqrt{s_{\mathrm{NN}}}>$ 40 GeV, while for $\sqrt{s_{\mathrm{NN}}}=$ 8 to 20 GeV the contribution from $D,\bar{D}$ decays to the intermediate mass dilepton spectra is subleading such that one should observe a rather clear signal from the QGP radiation. We, furthermore, study the $p_T$-spectra and the $R_{AA}(p_T)$ of single electrons at different energies as well as the excitation function of the inverse slope of the $m_T$- spectra for intermediate-mass dileptons from the QGP and from charm decays. We find moderate but characteristic changes in the inverse slope parameter for $\sqrt{s_{\mathrm{NN}}}>$ 20 GeV which can be observed experimentally in high statistics data. Additionally, we provide detailed predictions for dilepton spectra from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV.

    ↳ nucl-thhep-phPRC(2018)·64 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.