Thu·Dec 7, 2017Thursday·December 7, 2017

1. 01*

   Searching for New Physics with $b\to s{\tau }^{+}{\tau }^{-}$ processes

   Bernat Capdevila (Barcelona, Autonoma U. & Barcelona, IFAE)🇪🇸 · Andreas Crivellin (PSI, Villigen)🇨🇭 · Sébastien Descotes-Genon (Orsay, LPT)🇫🇷 · Lars Hofer (ICC, Barcelona U.)🇪🇸 · Joaquim Matias (Barcelona, Autonoma U. & Barcelona, IFAE)🇪🇸

   In recent years, intriguing hints for the violation of Lepton Flavour Universality (LFU) have been accumulated in semileptonic $B$ decays, both in the neutral-current transitions $b\to s{\ell }^{+}{\ell }^{-}$ (i.e., $R_K$ and $R_{K^{\ast }}$) and the charged-current transitions $b\to c{\ell }^{-}{\bar{\nu }}_{\ell }$ (i.e., $R_D$, $R_{D^{\ast }}$ and $R_{J/\psi }$). LHCb has reported deviations from the Standard Model (SM) expectations in $b\to s{\mu }^{+}{\mu }^{-}$ processes as well as in the ratios $R_K$ and $R_{K^{\ast }}$, which together point at New Physics (NP) affecting muons with a high significance. Furthermore, hints for LFU violation in $R_{D^{(\ast )}}$ and $R_{J/\psi }$ point at large deviations from the SM in processes involving tau leptons. Together, these hints for NP motivate the possibility of huge LFU-violating effects in $b\to s{\tau }^{+}{\tau }^{-}$ transitions. In this article we predict the branching ratios of $B\to K{\tau }^{+}{\tau }^{-}$, $B\to K^{\ast }{\tau }^{+}{\tau }^{-}$ and $B_s\to \varphi {\tau }^{+}{\tau }^{-}$ taking into account NP effects in the Wilson coefficients $C_{9{(}^{\prime })}^{\tau \tau }$ and $C_{10{(}^{\prime })}^{\tau \tau }$. Assuming a common NP explanation of $R_{D^{}}$ , $R_{D^{(\ast )}}$ and $R_{J/\psi }$, we show that a very large enhancement of $b\to s{\tau }^{+}{\tau }^{-}$ processes, of around three orders of magnitude compared to the SM, can be expected under fairly general assumptions. We find that the branching ratios of $B_s\to {\tau }^{+}{\tau }^{-}$, $B_s\to \varphi {\tau }^{+}{\tau }^{-}$ and $B\to K^{(\ast )}{\tau }^{+}{\tau }^{-}$ under these assumptions are in the observable range for LHCb and Belle II.

   hep-phhep-exPRL(2018)·138 citations
2. 02*

   Nuclear $p_{\perp }$-broadening of an energetic parton pair

   Florian Cougoulic🇫🇷 · Stéphane Peigné🇫🇷

   We revisit the transverse momentum broadening of a fast parton pair crossing a nuclear medium, putting emphasis on the pair global color state, for any number of colors $N$ and within the eikonal limit for parton propagation and the Gaussian approximation for the gluon field of the target. This study should provide the necessary tools to address nuclear broadening of $n$-parton systems in phenomenology while highlighting the color structure of the process.

   hep-phJHEP(2018)·8 citations
3. 03*

   Stability Analysis of the Chiral Transition in SU(4) Gauge Theory with Fermions in Multiple Representations

   Daniel C. Hackett🇺🇸

   We present a Pisarski-Wilczek stability analysis of SU(4) gauge theory coupled simultaneously to fermions charged under the fundamental and two-index antisymmetric representations of the gauge group. We carry out the calculation to one loop in the $ϵ$ expansion, assuming that the two species of fermion undergo a simultaneous chiral transition. The results indicate that the chiral transition is first order.

   hep-phhep-latPRD(2018)·4 citations
4. 04*

   Confronting the DAMPE Excess with the Scotogenic Type-II Seesaw Model

   Ran Ding🇨🇳 · Zhi-Long Han🇨🇳 · Lei Feng🇨🇳 · Bin Zhu🇨🇳

   The DArk Matter Particle Explorer (DAMPE) has observed a tentative peak at $E\sim 1.4\text{TeV}$ in the cosmic-ray electron spectrum. In this paper, we interpret this excess in the scotogenic type-II seesaw model. This model extends the canonical type-II seesaw model with dark matter (DM) candidates and a loop-induced vacuum expectation value of the triplet scalars, $v_{\Delta }$, resulting in small neutrino masses naturally even for TeV scale triplet scalars. Assuming a nearby DM subhalo, the DAMPE excess can be explained by DM annihilating into a pair of triplet scalars which subsequently decay to charged lepton final states. Spectrum fitting of the DAMPE excess indicates it potentially favors the inverted neutrino mass hierarchy. We also discuss how to evade associated neutrino flux in our model.

   hep-phCPC(2018)·32 citations
5. 05*

   Spectral Functions from the Functional Renormalization Group

   Jochen Wambach🇮🇹 · Christopher Jung🇩🇪 · Fabian Rennecke🇺🇸 · Ralf-Arno Tripolt🇩🇪 · Lorenz von Smekal🇩🇪

   We present results for in-medium spectral functions obtained within the Functional Renormalization Group framework. The analytic continuation from imaginary to real time is performed in a well-defined way on the level of the flow equations. Based on this recently developed method, results for the sigma and the pion spectral function for the quark-meson model are shown at finite temperature, finite quark-chemical potential and finite spatial momentum. It is shown how these spectral function become degenreate at high temperatures due to the restoration of chiral symmetry. In addition, results for vector- and axial-vector meson spectral functions are shown using a gauged linear sigma model with quarks. The degeneration of the $\rho$ and the $a_1$ spectral function as well as the behavior of their pole masses is discussed.

   hep-phhep-thnucl-thPoS(2018)·2 citations
6. 06*

   Synergies and complementarities between proposed future neutrino projects

   Sushant K. Raut🇰🇷

   Measuring the unknown neutrino oscillation parameters is one of the main aims in neutrino physics today. The measurement of these parameters is severely affected by the presence of degeneracies in the parameter space. Various neutrino oscillation projects have been proposed to measure them. In this overview talk, we will discuss some of the proposed neutrino experiments and the synergies between them that can enhance their future physics reach.

   hep-phPoS(2017)·1 citation
7. 07*

   Radiative neutrino masses from order-4 CP symmetry

   Igor P. Ivanov🇵🇹

   Generalized CP symmetry of order 4 (CP4) is surprisingly powerful in shaping scalar and quark sectors of multi-Higgs models. Here, we extend this framework to the neutrino sector. We build two simple Majorana neutrino mass models with unbroken CP4, which are analogous to Ma's scotogenic model. Both models use three Higgs doublets and two or three right-handed (RH) neutrinos. The minimal CP4 symmetric scotogenic model uses only two RH neutrinos, leads to three non-zero light neutrino masses, and contains a built-in mechanism to further suppress them via phase alignment. With three RH neutrinos, one generates a type I seesaw mass matrix of rank 1, which is then corrected by the same scotogenic mechanism, naturally leading to two neutrino mass scales with mild hierarchy. These minimal CP4-based constructions emerge as a primer for introducing additional symmetry structures and exploring their phenomenological consequences.

   hep-phJHEP(2018)·11 citations
8. 08*

   Gravitational form factors and angular momentum densities in light-front quark-diquark model

   Narinder Kumar🇮🇳 · Chandan Mondal🇨🇳 · Neetika Sharma🇮🇳

   We investigate the gravitational form factors (GFFs) and the longitudinal momentum densities ($p^{+}$ densities) for proton in a light-front quark-diquark model. The light-front wave functions are constructed from the soft-wall AdS/QCD prediction. The contributions from both the scalar and the axial vector diquarks are considered here. The results are compared with the consequences of a parametrization of nucleon generalized parton distributions (GPDs) in the light of recent MRST measurements of parton distribution functions (PDFs) and a soft-wall AdS/QCD model. The spatial distribution of angular momentum for up and down quarks inside the nucleon has been presented. At the density level, we illustrate different definitions of angular momentum explicitly for an up and down quark in the light-front quark-diquark model inspired by AdS/QCD.

   hep-phEPJA(2017)·32 citations
9. 09*

   Amplitude analysis of the anomalous decay ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\gamma$

   Ling-Yun Dai🇨🇳 · Xian-Wei Kang🇹🇼 · Ulf-G. Meißner🇩🇪 · Xin-Ying Song🇩🇪 · De-Liang Yao🇪🇸

   In this paper we perform an amplitude analysis of ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\gamma$ and confront it with the latest BESIII data. Based on the final-state interaction theorem, we represent the amplitude in terms of an Omnés function multiplied by a form factor that corresponds to the contributions from left-hand cuts and right-hand cuts in the inelastic channels. We also take into account the isospin violation effect induced by $\rho -\omega$ mixing. Our results show that the anomaly contribution is mandatory in order to explain the data. Its contribution to the decay width of $\Gamma ({\eta }^{\prime }\to \pi \pi \gamma )$ is larger than that induced by isospin violation. Finally we extract the pole positions of the $\rho$ and $\omega$ as well as their corresponding residues.

   hep-phnucl-thPRD(2018)·25 citations
10. 10*

    GR@PPA 2.9: radiation matching for simulating photon production processes in hadron collisions

    Shigeru Odaka🇯🇵 · Yoshimasa Kurihara🇯🇵

    We release an event generator package, GR@PPA 2.9, for simulating the direct (single) photon and diphoton (double photon) production in hadron collisions. The included programs were used in our previous studies, in which we have explicitly shown large contributions from parton-associated processes. The programs consistently combine simulations based on matrix elements with parton-shower simulations that reproduce the multiple parton radiation and quark fragmentation to photons. The matrix elements include associated parton production processes up to two partons. We provide instructions for the installation and execution of the programs in this article. The practical performance is also presented.

    hep-phComput.Phys.Commun.(2018)·0 citations
11. 11*

    Z-pole test of effective dark matter diboson interactions at the CEPC

    Mingjie Jin🇨🇳 · Yu Gao🇨🇳

    In this paper we investigate the projected sensitivity to effective dark matter (DM) - diboson interaction during the high luminosity $Z$-pole and 240 GeV runs at the proposed Circular Electron Positron Collider (CEPC). The proposed runs at the 91.2 GeV $e^{+}{e}^{-}$ center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the $Z$ boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible $Z$ boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model $\gamma \bar{\nu }\nu$ background. A projected sensitivity for effective $\gamma Z$ coupling efficient ${\kappa }_{\gamma Z}<(1030$ GeV${)}^{-3}$, $(1970$ GeV${)}^{-3}$ for scalar DM, ${\kappa }_{\gamma Z}<(360$ GeV${)}^{-3}$, $(540$ GeV${)}^{-3}$ for fermion DM are obtain for 25 fb${}^{-1}$ and 2.5 ab${}^{-1}$ $Z$-pole luminosities assuming the optimal low dark matter mass range. In comparison the effective DM-diphoton coupling sensitivity ${\kappa }_{\gamma \gamma }<(590$ GeV${)}^{-3}$ for scalar DM, ${\kappa }_{\gamma \gamma }<(360$ GeV${)}^{-3}$ for fermion DM are also obtained for a 5 ab${}^{-1}$ 240 GeV Higgs run. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators.

    hep-phEPJC(2018)·9 citations
12. 12*

    Nuclear parton distribution functions (nPDFs) and their uncertainties in the LHC Era

    S. Atashbar Tehrani🇮🇷

    We have presented the results of our next-to-next-to-leading order (NNLO) QCD analysis of nuclear parton distribution functions (nuclear PDFs) [Phys. Rev. D 93 (2016) 014026, arXiv:1601.00939 [hep-ph]] using all available neutral current charged-lepton (${\ell }^{\pm }$ + nucleus) deeply inelastic scattering (DIS) data as well as Drell-Yan (DY) cross-section ratios ${\sigma }_{\mathrm{DY}}^A/{\sigma }_{\mathrm{DY}}^{A^{\prime }}$ for a variety of nuclear targets. We have studied in detail the parametrizations and the atomic mass (A) dependence of the nuclear PDFs at NNLO at the input scale, $Q_0^2=2\mathrm{Ge}{\mathrm{V}}^2$. Our {\tt KA15} nuclear PDFs provides a complete set of nuclear PDFs, $f_i^{(A,Z)}(x,Q^2)$, with a full functional dependence on $x$, A, $Q^2$. The uncertainties of the obtained nuclear modification factors for each parton flavour as well as the corresponding observables are estimated using the well-known Hessian method. The nuclear heavy quark contributions are also included into the analysis in the framework of zero-mass variable flavour number scheme (ZM-VFNS). We compare the results of our parametrization with all available nuclear DIS data and the results of other nuclear PDFs groups. We have found that our nuclear PDFs to be in reasonably good agreement with results in the literature. The estimates of errors provided by our global analysis ({\tt KA15}) are rather smaller than those of other groups. We have briefly reviewed different aspects of recent LHC heavy-ion collisions data including the first experimental data from the LHC proton+lead ($p-pb$) and lead+lead ($pb-pb$) run which can be used in the global fits of nuclear PDFs.

    hep-phnucl-exKnE Energ.Phys.(2018)·4 citations
13. 13*

    The Mellin-Barnes Approach to Hadronic Vacuum Polarization and $g_{\mu }-2$

    Jérôme Charles🇫🇷 · David Greynat🇫🇷 · Eduardo de Rafael🇫🇷

    It is shown that with a precise determination of a few derivatives of the hadronic vacuum polarization (HVP) self-energy function $\Pi (Q^2)$ at $Q^2=0$, from lattice QCD (LQCD) or from a dedicated low-energy experiment, one can obtain an evaluation of the lowest order HVP contribution to the anomalous magnetic moment of the muon $a_{\mu }^{\mathrm{HVP}}$ with an accuracy comparable to the one reached using the $e^{+}{e}^{-}$ annihilation cross-section into hadrons. The technique of Mellin-Barnes approximants (MBa) that we propose is illustrated in detail with the example of the two loop vacuum polarization function in QED. We then apply it to the first few moments of the hadronic spectral function obtained from experiment and show that the resulting MBa evaluations of $a_{\mu }^{\mathrm{HVP}}$ converge very quickly to the full experimental determination.

    hep-phhep-latPRD(2018)·22 citations
14. 14*

    Fully-differential Top-Pair Production at a Lepton Collider: From Threshold to Continuum

    Fabian Bach · Bijan Chokoufé Nejad🇩🇪 · Andre Hoang🇦🇹 · Wolfgang Kilian🇩🇪 · Jürgen Reuter🇩🇪 · Maximilian Stahlhofen🇩🇪 · Thomas Teubner🇬🇧 · Christian Weiss🇩🇪

    We present an approach to predict exclusive $W^{+}b{W}^{-}\bar{b}$ production at lepton colliders that correctly describes the top-anti-top threshold as well as the continuum region. We incorporate $t\bar{t}$ form factors for the NLL threshold resummation derived in NRQCD into a factorized relativistic cross section using an extended double-pole approximation, which accounts for fixed-order QCD corrections to the top decays at NLO. This is combined with the full fixed-order QCD result at NLO for $W^{+}b{W}^{-}\bar{b}$ production to obtain predictions that are not only valid at threshold but smoothly transition to the continuum region. Our implementation is based on the Monte Carlo event generator WHIZARD and the code TOPPIK and allows to compute fully-differential threshold-resummed cross sections including the interference with non-resonant background processes. For the first time it is now possible to systematically study general differential observables at future lepton colliders involving the decay products of the top quarks at energies close to the pair production threshold and beyond.

    hep-phhep-exJHEP(2018)·56 citations
15. 15*

    A first look at two-loop five-gluon scattering in QCD

    Simon Badger🇬🇧 · Christian Brønnum-Hansen🇬🇧 · Heribertus Bayu Hartanto🇬🇧 · Tiziano Peraro🇩🇪

    We compute the leading colour contributions to five-gluon scattering at two loops in massless QCD. The integrands of all independent helicity amplitudes are evaluated using d-dimensional generalised unitarity cuts and finite field reconstruction techniques. Numerical evaluation of the integral basis is performed with sector decomposition methods to obtain the first benchmark results for all helicity configurations of a 2 to 3 scattering process in QCD.

    hep-phhep-thPRL(2018)·137 citations
16. 16*

    QCD-constrained dynamical spin effects in the pion holographic light-front wavefunction

    Mohammad Ahmady🇨🇦 · Farrukh Chishtie🇨🇦 · Ruben Sandapen🇨🇦

    Using light-front holography, we predict simultaneously the pion decay constant and the pion charge radius by taking into account (higher twist) dynamical spin effects whose relative importance is constrained by QCD.

    hep-phFew Body Syst.(2018)·0 citations
17. 17*

    Towards New Frontiers with $B\to \pi K$ Decays

    Robert Fleischer🇳🇱 · Ruben Jaarsma🇳🇱 · K. Keri Vos🇩🇪

    Exploring correlations between the CP asymmetries of $B_d^0\to {\pi }^0{K}_{\mathrm{S}}$ following from an isospin relation, we uncover new tensions with the Standard Model in data for neutral $B\to \pi K$ decays. Should this intriguing picture originate from New Physics, a modified electroweak penguin sector provides a key scenario. It includes models with extra $Z^{\prime }$ bosons, which offer attractive ways to resolve anomalies in $B\to K^{(\ast )}{\ell }^{+}{\ell }^{-}$ measurements. We present a new strategy to reveal the underlying physics, apply it to current $B\to \pi K$ data, and discuss the excellent prospects for Belle II.

    hep-phhep-exPLB(2018)·40 citations
18. 18*

    Catching a New Force by the Tail

    Simone Alioli🇨🇭 · Marco Farina🇺🇸 · Duccio Pappadopulo🇺🇸 · Joshua T. Ruderman🇺🇸

    The Large Hadron Collider (LHC) is sensitive to new heavy gauge bosons that produce narrow peaks in the dilepton invariant mass spectrum up to about $m_{Z^{\prime }}\sim 5$ TeV. $Z^{\prime }$s that are too heavy to produce directly can reveal their presence through interference with Standard Model dilepton production. We show that the LHC can significantly extend the mass reach for such $Z^{\prime }$s by performing precision measurements of the shape of the dilepton invariant mass spectrum. The high luminosity LHC can exclude, with 95$\%$ confidence, new gauge bosons as heavy as $m_{Z^{\prime }}\sim 10-20$ TeV that couple with gauge coupling strength of $g_{Z^{\prime }}\sim 1-2$.

    hep-phPRL(2018)·78 citations
19. 19*

    Better Higgs-CP Tests Through Information Geometry

    Johann Brehmer🇺🇸 · Felix Kling🇺🇸 · Tilman Plehn🇩🇪 · Tim M.P. Tait🇺🇸

    Measuring the CP symmetry in the Higgs sector is one of the key tasks of the LHC and a crucial ingredient for precision studies, for example in the language of effective Lagrangians. We systematically analyze which LHC signatures offer dedicated CP measurements in the Higgs-gauge sector, and discuss the nature of the information they provide. Based on the Fisher information measure, we compare the maximal reach for CP-violating effects in weak boson fusion, associated ZH production, and Higgs decays into four leptons. We find a subtle balance between more theory-independent approaches and more powerful analysis channels, indicating that rigorous evidence for CP violation in the Higgs-gauge sector will likely require a multi-step process.

    hep-phPRD(2018)·78 citations
20. 20*

    Low-scale Gauge Mediation after LHC Run 2

    Xiaochuan Lu🇺🇸 · Satoshi Shirai🇯🇵

    We study low-scale gauge mediated supersymmetry breaking models with a very light gravitino of mass $\mathcal{O}(1)$ eV. The cosmological upper bound on the gravitino mass and the collider constraints on the sparticle masses give a significant impact on such models. We apply the latest results of the LHC to these models and obtain the current constraints. We find that perturbatively calculable classes of low-scale gauge mediation models can be largely excluded.

    hep-phPLB(2018)·3 citations
21. 21*

    Complex Masses of Mesons and Resonances In Relativistic Quantum Mechanics

    M. N. Sergeenko🇧🇾

    Relativistic bound state problem in hadron physics is studied. Mesons and their resonance excitations in the framework of Relativistic Quantum Mechanics (RQM) are investigated. Two-particle wave equation for the Lorentz scalar QCD inspired funnel-type potential with the coordinate dependent strong coupling ${\alpha }_{\S }(r)$ is derived. The concept of distance dependent particle mass is developed. Two exact asymptotic expressions for the system's squared mass are obtained and used to derive the meson interpolating complex-mass formula. Free particle hypothesis for the bound state is developed: quark and antiquark move as free particles in of the bound system. Practical applications of the model are given.

    hep-ph3 citations
22. 22*

    The Weak Gravity Conjecture and Emergence from an Ultraviolet Cutoff

    Ben Heidenreich🇨🇦 · Matthew Reece🇺🇸 · Tom Rudelius🇺🇸

    We study ultraviolet cutoffs associated with the Weak Gravity Conjecture (WGC) and Sublattice Weak Gravity Conjecture (sLWGC). There is a magnetic WGC cutoff at the energy scale $e{G}_N^{-1/2}$ with an associated sLWGC tower of charged particles. A more fundamental cutoff is the scale at which gravity becomes strong and field theory breaks down entirely. By clarifying the nature of the sLWGC for nonabelian gauge groups we derive a parametric upper bound on this strong gravity scale for arbitrary gauge theories. Intriguingly, we show that in theories approximately saturating the sLWGC, the scales at which loop corrections from the tower of charged particles to the gauge boson and graviton propagators become important are parametrically identical. This suggests a picture in which gauge fields emerge from the quantum gravity scale by integrating out a tower of charged matter fields. We derive a converse statement: if a gauge theory becomes strongly coupled at or below the quantum gravity scale, the WGC follows. We sketch some phenomenological consequences of the UV cutoffs we derive.

    ↳ hep-thhep-phEPJC(2018)·180 citations
23. 23*

    On Synthetic Gravitational Waves from Multi-field Inflation

    Ogan Özsoy🇬🇧

    We revisit the possibility of producing observable tensor modes through a continuous particle production process during inflation. Particularly, we focus on the multi-field realization of inflation where a spectator pseudo-scalar $\sigma$ induces a significant amplification of the $\mathrm{U}(1)$ gauge fields through the coupling $\propto \sigma F_{\mu \nu }{\tilde{F}}^{\mu \nu }$. In this model, both the scalar $\sigma$ and the Abelian gauge fields are gravitationally coupled to the inflaton sector, therefore they can only affect the primordial scalar and tensor fluctuations through their mixing with gravitational fluctuations. Recent studies on this scenario show that the sourced contributions to the scalar correlators can be dangerously large to invalidate a large tensor power spectrum through the particle production mechanism. In this paper, we re-examine these recent claims by explicitly calculating the dominant contribution to the scalar power and bispectrum. Particularly, we show that once the current limits from CMB data are taken into account, it is still possible to generate a signal as large as $r\approx 10^{-3}$ and the limitations on the model building are more relaxed than what was considered before.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2018)·36 citations
24. 24*

    TOP2017: Experimental Summary

    Andrea Giammanco🇧🇪

    At the time of the 10th International Workshop on Top Quark Physics (TOP2017), top quark physics is a very dynamic research area. Thanks to the unprecedentedly fast accumulation of high-energy data at the LHC during the ongoing Run~2, statistical starvation is a matter of the past for most of the traditional top-quark analyses, that are now experiencing the luxury of having to worry about how to punch through the "Systematics Wall" and maximize the utility of their data. New processes involving top quarks are being studied for the first time, and the good old pair-production processes are being explored in unusual settings, such as collisions involving heavy ions, or "reference data" collected by the LHC at relatively low centre-of-mass energy. The TOP2017 conference featured 37 talks delivered by experimental physicists, including seven in the "Young Scientists Forum" where young colleagues were given the opportunity to elaborate more deeply than usual on their own work. As it is impossible to do justice to all the experimental results presented at this conference while staying within a reasonable length, this document contains a very biased selection, mostly based on the personal taste of the author.

    ↳ hep-exhep-ph1 citation
25. 25*

    Plasmon mass scale in two dimensional classical nonequilibrium gauge theory

    Tuomas Lappi🇫🇮 · Jarkko Peuron🇫🇮

    We study the plasmon mass scale in weakly coupled strongly interacting nonabelian gauge theory in a two dimensional configuration that mimics the boost invariant initial color fields in a heavy ion collision. We numerically measure the plasmon mass scale using three different methods: a Hard Thermal Loop (HTL) expression involving the quasiparticle spectrum constructed from Coulomb gauge field correlators, an effective dispersion relation and the measurement of oscillations between electric and magnetic energies after introducing a spatially uniform perturbation to the electric field. We find that the hard thermal loop expression and the uniform electric field measurement are in rough agreement. The effective dispersion relation agrees with other methods within a factor of two. We also study the dependence on time and occupation number, observing similar trends as in three spatial dimensions, where a power law dependence sets in after an occupation number dependent transient time. We observe a decrease of the plasmon mass squared as $t^{\frac{-1}{3}}$ at late times.

    ↳ hep-lathep-phPRD(2018)·11 citations
26. 26*

    Abelian and non-Abelian Berry curvatures in lattice QCD

    Shi Pu🇯🇵 · Arata Yamamoto🇯🇵

    We studied the Berry curvature of the massive Dirac fermion in 3+1 dimensions. For the non-interacting Dirac fermion, the Berry curvature is non-Abelian because of the degeneracy of positive and negative helicity modes. We calculated the non-Abelian Berry curvature analytically and numerically. For the interacting Dirac fermion in QCD, the degeneracy is lost because gluons carry helicity and color charge. We calculated the Abelian Berry curvature in lattice QCD.

    ↳ hep-lathep-phNPB(2018)·6 citations
27. 27*

    Limits on stellar-mass compact objects as dark matter from gravitational lensing of type Ia supernovae

    Miguel Zumalacarregui🇺🇸 · Uros Seljak🇺🇸

    The nature of dark matter (DM) remains unknown despite very precise knowledge of its abundance in the universe. An alternative to new elementary particles postulates DM as made of macroscopic compact halo objects (MACHO) such as black holes formed in the very early universe. Stellar-mass primordial black holes (PBHs) are subject to less robust constraints than other mass ranges and might be connected to gravitational-wave signals detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). New methods are therefore necessary to constrain the viability of compact objects as a DM candidate. Here we report bounds on the abundance of compact objects from gravitational lensing of type Ia supernovae (SNe). Current SNe datasets constrain compact objects to represent less than 35.2% (Joint Lightcurve Analisis) and 37.2% (Union 2.1) of the total matter content in the universe, at 95% confidence-level. The results are valid for masses larger than $\sim 0.01M_{\odot }$ (solar-masses), limited by the size SNe relative to the lens Einstein radius. We demonstrate the mass range of the constraints by computing magnification probabilities for realistic SNe sizes and different values of the PBH mass. Our bounds are sensitive to the total abundance of compact objects with $M\lesssim 0.01M_{\odot }$ and complementary to other observational tests. These results are robust against cosmological parameters, outlier rejection, correlated noise and selection bias. PBHs and other MACHOs are therefore ruled out as the dominant form of DM for objects associated to LIGO gravitational wave detections. These bounds constrain early-universe models that predict stellar-mass PBH production and strengthen the case for lighter forms of DM, including new elementary particles.

    ↳ astro-ph.COastro-ph.HEgr-qchep-ph+1PRL(2018)·316 citations
28. 28*

    Rings: an efficient Java/Scala library for polynomial rings

    Stanislav Poslavsky🇷🇺

    In this paper we briefly discuss \Rings --- an efficient lightweight library for commutative algebra. Polynomial arithmetic, GCDs, polynomial factorization and Gröbner bases are implemented with the use of modern asymptotically fast algorithms. \Rings can be easily interacted or embedded in applications in high-energy physics and other research areas via a simple API with fully typed hierarchy of algebraic structures and algorithms for commutative algebra. The use of the Scala language brings a quite novel powerful, strongly typed functional programming model allowing to write short, expressive, and fast code for applications. At the same time Rings shows one of the best performances among existing software for algebraic calculations. \Rings is available from http://github.com/PoslavskySV/rings

    ↳ cs.SCcs.MShep-phmath.AC+1Comput.Phys.Commun.(2019)·3 citations
29. 29*

    Infrared Divergences and Quantum Coherence

    Cesar Gomez🇪🇸 · Raoul Letschka🇪🇸 · Sebastian Zell🇩🇪

    In theories with long-range forces like QED or perturbative gravity, only rates that include emitted soft radiation are non-vanishing. Independently of detector resolution, finite observables can only be obtained after integrating over the IR-component of this radiation. This integration can lead to some loss of quantum coherence. In this note, however, we argue that it should in general not lead to full decoherence. Based on unitarity, we suggest a way to define non-vanishing off-diagonal pieces of the IR-finite density matrix. For this IR-finite density matrix, we estimate the dependence of the loss of quantum coherence, i.e. of its purity, on the scattering kinematics.

    ↳ hep-thgr-qchep-phquant-phEPJC(2018)·30 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.