Mon·Mar 28, 2016Monday·March 28, 2016

1. 01*

   Irrelevance of $f_0(500)$ in bulk thermal properties

   Francesco Giacosa🇩🇪 · Viktor Begun🇵🇱 · Wojciech Broniowski🇵🇱

   We discuss why the scalar-isoscalar resonance $f_0(500)$ should in practice not be included in thermal models describing the freeze-out of heavy-ion collisions. Its contribution into pion multiplicities is in principle relevant because it is light and it decays only into pions. However, it is cancelled to a very good numerical precision by the non-resonant scalar-isotensor repulsion among pions. Our approach is an application of a well-known theorem relating spectral function to phase shifts. The numerical results are solely based on pion-pion scattering data and thus model independent.

   hep-phActa Phys.Polon.Supp.(2016)·7 citations
2. 02*

   Back to 1974: The $\mathcal{Q}$-onium

   Jernej F. Kamenik🇸🇮 · Michele Redi🇮🇹

   We show that the 750 GeV di-photon excess could be explained by the $\mathcal{Q}-$onium system of a new QCD-like theory with fermions vectorial under the SM. Beside the spin-0 di-photon singlet this scenario predicts almost degenerate colored scalars and spin-1 resonances analogous to the $J/\Psi$ in QCD. All these states are within the reach of the LHC. An apparent large width can be explained as due to production of excited states with splitting $\Delta m\sim \Gamma$.

   hep-phPLB(2016)·19 citations
3. 03*

   Vector Boson Fusion Searches for Dark Matter at the LHC

   James Brooke🇬🇧 · Matthew R. Buckley🇺🇸 · Patrick Dunne🇬🇧 · Bjoern Penning🇬🇧 · John Tamanas🇺🇸 · Miha Zgubic🇬🇧

   The vector boson fusion (VBF) event topology at the Large Hadron Collider (LHC) allows efficient suppression of dijet backgrounds and is therefore a promising target for new physics searches. We consider dark matter models which interact with the Standard Model through the electroweak sector: either through new scalar and pseudoscalar mediators which can be embedded into the Higgs sector, or via effective operators suppressed by some higher scale, and therefore have significant VBF production cross-sections. Using realistic simulations of the ATLAS and CMS analysis chain, including estimates of major error sources, we project the discovery and exclusion potential of the LHC for these models over the next decade.

   hep-phhep-exPRD(2016)·22 citations
4. 04*

   On the ultimate precision of meson mixing observables

   Thomas Jubb🇬🇧 · Matthew Kirk🇬🇧 · Alexander Lenz🇬🇧 · Gilberto Tetlalmatzi-Xolocotzi🇬🇧

   Meson mixing is considered to be an ideal candidate for new physics searches. Current experimental precision has greatly increased over the recent years, excelling in several cases the theoretical precision. A possible limit in the theoretical accuracy could be a hypothetical breakdown of quark-hadron duality. We propose a simple model for duality violations and give stringent bounds on such effects for mixing observables, indicating regions, where future measurements of $\Delta {\Gamma }_d$, $a_{sl}^d$ and $a_{sl}^s$ would be clear signals of new physics. Finally, we turn our attention to the charm sector, and reveal that already a modest duality violation of about $20\%$ could explain the huge difference between HQE predictions for D-mixing and experimental data.

   hep-phhep-exNPB(2017)·83 citations
5. 05*

   BFKL Azimuthal Imprints in Inclusive Three-jet Production at 7 and 13 TeV

   F. Caporale🇪🇸 · F. G. Celiberto🇮🇹 · G. Chachamis🇪🇸 · D. Gordo Gomez🇪🇸 · A Sabio Vera🇪🇸

   We propose the study of new observables in LHC inclusive events with three tagged jets, one in the forward direction, one in the backward direction and both well-separated in rapidity from the each other (Mueller-Navelet jets), together with a third jet tagged in central regions of rapidity. Since non-tagged associated mini-jet multiplicity is allowed, we argue that projecting the cross sections on azimuthal-angle components can provide several distinct tests of the BFKL dynamics. Realistic LHC kinematical cuts are introduced.

   hep-phNPB(2016)·83 citations
6. 06*

   Strangeness $S=-1$ hyperon-nucleon scattering in covariant chiral effective field theory

   Kai-Wen Li🇨🇳 · Xiu-Lei Ren🇨🇳 · Li-Sheng Geng🇨🇳 · Bing-Wei Long🇨🇳

   Motivated by the successes of covariant baryon chiral perturbation theory in one-baryon systems and in heavy-light systems, we study relevance of relativistic effects in hyperon-nucleon interactions with strangeness $S=-1$. In this exploratory work, we follow the covariant framework developed by Epelbaum and Gegelia to calculate the $YN$ scattering amplitude at leading order. By fitting the five low-energy constants to the experimental data, we find that the cutoff dependence is mitigated, compared with the heavy-baryon approach. Nevertheless, the description of the experimental data remains quantitatively similar at leading order.

   hep-phnucl-thPRD(2016)·45 citations
7. 07*

   Update of HKN Nuclear PDFs

   Masanori Hirai🇯🇵

   We discuss consistency of the nuclear effects between the electromagnetic and weak interactions. In order to study a possibility of different nuclear effects in the neutrino DIS process, double differential cross section data are compared with these values obtained by the HKN07 nuclear parton distribution functions (nPDFs). Discrepancies are found in the small and large-$x$ regions, and difference of kinematical value $y$ dependence exists between the $\nu$ and $\bar{\nu }$ data around $x=0.35$. Moreover, we study statistical significance of the neutrino DIS data in each $x$ bin and discuss about the possibility of the different nuclear modifications.

   hep-phhep-exnucl-exnucl-thJPS Conf.Proc.(2016)·4 citations
8. 08*

   Twist-3 effect from the longitudinally polarized proton for $A_{LT}$ in hadron production from $pp$ collisions

   Yuji Koike🇯🇵 · Daniel Pitonyak🇺🇸 · Shinsuke Yoshida🇨🇳

   We compute the contribution from the longitudinally polarized proton to the twist-3 double-spin asymmetry $A_{LT}$ in inclusive (light) hadron production from proton-proton collisions,i.e., $p^{\uparrow }\vec{p}\to hX$. We show that using the relevant QCD equation-of-motion relation and Lorentz invariance relation allows one to eliminate the twist-3 quark-gluon correlator (associated with the longitudinally polarized proton) in favor of one-variable twist-3 quark distributions and the (twist-2) transversity parton density. Including this result with the twist-3 pieces associated with the transversely polarized proton and unpolarized final-state hadron (which have already been calculated in the literature), we now have the complete leading-order cross section for this process.

   hep-phhep-exPLB(2016)·13 citations
9. 09*

   Probing the SUSY with $10$ TeV stop mass in rare decays and CP violation of Kaon

   Morimitsu Tanimoto🇯🇵 · Kei Yamamoto🇯🇵

   We probe the SUSY at the $10\mathrm{TeV}$ scale in the rare decays and the CP violation of the kaon. We focus on the processes of $K_L\to {\pi }^0\nu \bar{\nu }$ and $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ combined with the CP violating parameters ${ϵ}_K$ and ${ϵ}_K^{\prime }/{ϵ}_K$. The Z-penguin mediated by the chargino loop cannot enhance $K_L\to {\pi }^0\nu \bar{\nu }$ and $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ because the left-right mixing of the stop is constrained by the $125$ GeV Higgs mass. On the other hand, the Z-penguin mediated by the gluino loop can enhance the branching ratios of both $K_L\to {\pi }^0\nu \bar{\nu }$ and $K^{+}\to {\pi }^{+}\nu \bar{\nu }$. The former increases up to more than $1.0\times 10^{-10}$, which is much larger than the SM prediction even if the constraint of ${ϵ}_K$ is imposed. It is remarkable that the Z-penguin mediated by the gluino loop can enhance simultaneously ${ϵ}_K^{\prime }/{ϵ}_K$ and the branching ratio of $K_L\to {\pi }^0\nu \bar{\nu }$, which increases up to $1.0\times 10^{-10}$. We also study the decay rates of $K_L\to {\mu }^{+}{\mu }^{-}$, $B^0\to {\mu }^{+}{\mu }^{-}$ and $B_s\to {\mu }^{+}{\mu }^{-}$, which correlate with the $K_L\to {\pi }^0\nu \bar{\nu }$ decay through the Z penguin. It is important to examine the $B^0\to {\mu }^{+}{\mu }^{-}$ process since we expect the enough sensitivity of this decay mode to the SUSY at LHCb.

   hep-phPTEP(2016)·57 citations
10. 10*

    A critical reassessment of particle Dark Matter limits from dwarf satellites

    Piero Ullio🇮🇹 · Mauro Valli🇮🇹

    Dwarf satellite galaxies are ideal laboratories for identifying particle Dark Matter signals. When setting limits on particle Dark Matter properties from null searches, it becomes however crucial the level at which the Dark Matter density profile within these systems is constrained by observations. In the limit in which the spherical Jeans equation is assumed to be valid for a given tracer stellar population, we study the solution of this equation having the Dark Matter mass profile as an output rather than as a trial parametric input. Within our new formulation, we address to what level dwarf spheroidal galaxies feature a reliable mass estimator. We assess then possible extrapolation of the density profiles in the inner regions and -- keeping explicit the dependence on the orbital anisotropy profile of the tracer population -- we derive general trends on the line-of-sight integral of the density profile squared, a quantity commonly dubbed $J$-factor and crucial to estimate fluxes from prompt Dark Matter pair annihilations. Taking Ursa Minor as a study case among Milky Way satellites, we perform Bayesian inference using the available kinematical data for this galaxy. Contrary to all previous studies, we avoid marginalization over quantities poorly constrained by observations or by theoretical arguments. We find minimal $J$-factors to be about 2 to 4 times smaller than commonly quoted estimates, approximately relaxing by the same amount the limit on Dark Matter pair annihilation cross section from gamma-ray surveys of Ursa Minor. At the same time, if one goes back to a fixed trial parametric form for the density, e.g. using a NFW or Burkert profile, we show that the minimal $J$ can hardly be reduced by more than a factor of 1.5.

    ↳ astro-ph.GAhep-phJCAP(2016)·66 citations
11. 11*

    Mixed symmetry tensors in the worldline formalism

    Olindo Corradini🇮🇹 · James P. Edwards🇬🇧

    We consider the first quantised approach to quantum field theory coupled to a non-Abelian gauge field. Representing the colour degrees of freedom with a single family of auxiliary variables the matter field transforms in a reducible representation of the gauge group which - by adding a suitable Chern-Simons term to the particle action - can be projected onto a chosen fully (anti-)symmetric representation. By considering F families of auxiliary variables, we describe how to extend the model to arbitrary tensor products of F reducible representations, which realises a U(F) "flavour" symmetry on the worldline particle model. Gauging this symmetry allows the introduction of constraints on the Hilbert space of the colour fields which can be used to project onto an arbitrary irreducible representation, specified by a certain Young Tableau. In particular the occupation numbers of the wavefunction - i.e. the lengths of the columns (rows) of the Young Tableau - are fixed through the introduction of Chern-Simons terms. We verify this projection by calculating the number of colour degrees of freedom associated to the matter field. We suggest that, using the worldline approach to quantum field theory, this mechanism will allow the calculation of one-loop scattering amplitudes with the virtual particle in an arbitrary representation of the gauge group.

    ↳ hep-thhep-phmath-phmath.MPJHEP(2016)·21 citations
12. 12*

    Nonconservation of lepton current and asymmetry of relic neutrinos

    Maxim Dvornikov (1 and 2)🇷🇺 · Victor B. Semikoz (1) ((1) IZMIRAN, (2) Tomsk State University)🇷🇺

    The neutrino asymmetry in the early universe plasma, $n_{\nu }-n_{\bar{\nu }}$, is calculated both before and after the electroweak phase transition (EWPT). The leptogenesis before EWPT within the standard model is well known to be driven by the abelian anomaly in a massless hypercharge field. The generation of the neutrino asymmetry in the Higgs phase after EWPT, in its turn, has not been considered previously because of the absence of any quantum anomaly in an external electromagnetic field for such electroneutral particles as neutrino, unlike the Adler anomaly for charged left and right polarized massless electrons in the same electromagnetic field. Using the neutrino Boltzmann equation, modified by the Berry curvature term in the momentum space, we establish the violation of the macroscopic neutrino current in plasma after EWPT and exactly reproduce the nonconservation of the lepton current in the symmetric phase before EWPT arising in quantum field theory due to the non-zero lepton hypercharge and corresponding triangle anomaly in an external hypercharge field. In the last case the violation of the lepton current is derived through the kinetic approach without the computation of the corresponding Feynman diagrams. Then the new kinetic equation is applied for the calculation of the neutrino asymmetry accounting for the the Berry curvature and the electroweak interaction with background fermions in the Higgs phase, including the stage after the neutrino decoupling at the absence of neutrino collisions in plasma. This asymmetry is found to be rather small to be observed. Thus, a difference of the relic neutrino and antineutrino densities, if exists, should be acquired mainly in the symmetric phase before EWPT.

    ↳ astro-ph.COhep-phJ.Exp.Theor.Phys.(2017)·5 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.