Fri·Jan 22, 2016Friday·January 22, 2016

1. 01*

   NNLO QCD predictions for fully-differential top-quark pair production at the Tevatron

   Michal Czakon🇩🇪 · Paul Fiedler🇩🇪 · David Heymes🇬🇧 · Alexander Mitov🇬🇧

   We present a comprehensive study of differential distributions for Tevatron top-pair events at the level of stable top quarks. All calculations are performed in NNLO QCD with the help of a fully differential partonic Monte-Carlo and are exact at this order in perturbation theory. We present predictions for all kinematic distributions for which data exists. Particular attention is paid on the top-quark forward-backward asymmetry which we study in detail. We compare the NNLO results with existing approximate NNLO predictions as well as differential distributions computed with different parton distribution sets. Theory errors are significantly smaller than current experimental ones with overall agreement between theory and data.

   hep-phhep-exJHEP(2016)·163 citations
2. 02*

   Review of Neutrino Oscillations With Sterile and Active Neutrinos

   Leonard S. Kisslinger🇺🇸

   Recently neutrino oscillation experiments have shown that it is very likely that there are one or two sterile neutrinos. In this review neutrino oscillations with one, two, three sterile and three active neutrinos, and parameters that are consistent with experiments, are reviewed.

   hep-phInt.J.Mod.Phys.A(2016)·3 citations
3. 03*

   Excitation of Chandrasekhar-Kendall photons in Quark Gluon Plasma by an ultrarelativitsic quark

   Kirill Tuchin🇺🇸

   A quark propagating through the quark gluon plasma and scattering off the thermal gluons can radiate photons in states with definite angular momentum and magnetic helicity. These states, known as the Chandrasekhar-Kendall states, are eigenstates of the curl operator and have a non-trivial topology. I compute spectrum of these states in the ultrarelativistic limit and study its properties.

   hep-phPRC(2016)·8 citations
4. 04*

   Charm-quark production in deep-inelastic neutrino scattering at NNLO in QCD

   Edmond L. Berger🇺🇸 · Jun Gao🇺🇸 · Chong Sheng Li🇨🇳 · Ze Long Liu🇨🇳 · Hua Xing Zhu🇺🇸

   We present a fully differential next-to-next-to-leading order calculation of charm quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti-)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nucleon.

   hep-phhep-exPRL(2016)·57 citations
5. 05*

   TikZ-Feynman: Feynman diagrams with TikZ

   Joshua Ellis🇦🇺

   TikZ-Feynman is a LaTeX package allowing Feynman diagrams to be easily generated within LaTeX with minimal user instructions and without the need of external programs. It builds upon the TikZ package and leverages the graph placement algorithms from TikZ in order to automate the placement of many vertices. TikZ-Feynman still allows fine-tuned placement of vertices so that even complex diagrams can still be generated with ease.

   hep-phComput.Phys.Commun.(2017)·451 citations
6. 06*

   Tetraquark state candidates: $Y(4260)$, $Y(4360)$, $Y(4660)$ and $Z_c(4020/4025)$

   Zhi-Gang Wang🇨🇳

   In this article, we construct the axialvector-diquark-axialvector-antidiquark type tensor current to interpolate both the vector and axialvector tetraquark states, then calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and obtain the QCD sum rules for both the vector and axialvector tetraquark states. The numerical results support assigning the $Z_c(4020/4025)$ to be the $J^{PC}=1^{+-}$ diquark-antidiquark type tetraquark state, and assigning the $Y(4660)$ to be the $J^{PC}=1^{--}$ diquark-antidiquark type tetraquark state. Furthermore, we take the $Y(4260)$ and $Y(4360)$ as the mixed charmonium-tetraquark states, and construct the two-quark-tetraquark type tensor currents to study the masses and pole residues. The numerical results support assigning the $Y(4260)$ and $Y(4360)$ to be the mixed charmonium-tetraquark states.

   hep-phEPJC(2016)·94 citations
7. 07*

   Graviton Kaluza Klein modes in non-flat branes with stabilised modulus

   Tanmoy Paul🇮🇳 · Soumitra Sengupta🇮🇳

   We consider a generalised two brane Randall Sundrum model where the branes are endowed with non-zero cosmological constant. In this scenario, we re-examine the modulus stabilisation mechanism and the nature of Kaluza Klein (KK) graviton modes. Our result reveals that while the KK mode graviton masses may change significantly with brane cosmological constant, the Goldberger-Wise stabilisation mechanism, which assumes negligible backreaction on the background metric, continues to hold even when the branes have large cosmological constant. The possibility of having a global minimum for the modulus is also discussed.

   hep-phhep-thPRD(2016)·14 citations
8. 08*

   Production of pentaquarks in $pA$-collisions

   Ivan Schmidt🇨🇱 · M. Siddikov🇨🇱

   We argue that a hidden-charm pentaquark recently observed in weak decays of ${\Lambda }_b$ can be produced in proton-nucleus collisions without electroweak intermediaries. We analyze the production cross-section for several scenarios of internal structure and find that a cross-section is sizable. This process can be studied both in collider as well as in fixed-target experiments. In the former case, the pentaquarks are produced at very forward rapidities, whereas in the latter case, pentaquarks are produced with relatively small rapidities and can be easily detected via invariant mass distribution of a forward $J/\psi$ and a comoving proton. Additionally, the suggested process allows to check the existence of a neutral pentaquark $P_c^0$ (an isospin partner of $P_c^{+}$) predicted in several models. The rapidity and transverse momentum distributions of pentaquarks could provide comprehensive information about the $\bar{c}c$ component of this exotic baryon.

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

   Charmonia in a Contact Interaction

   Marco A. Bedolla🇲🇽 · J.J. Cobos-Martínez🇲🇽 · Adnan Bashir🇲🇽

   For the flavour-singlet heavy quark system of charmonia, we compute the masses of the ground state mesons in four different channels: pseudo-scalar (${\eta }_c(1S)$), vector ($J/\Psi (1S)$), scalar (${\chi }_{c_0}(1P)$) and axial vector (${\chi }_{c_1}(1P)$), as well as the weak decay constants of the ${\eta }_c(1S)$ and $J/\Psi (1S)$ and the charge radius of ${\eta }_c(1S)$. The framework for this analysis is provided by a symmetry-preserving Schwinger-Dyson equation (SDEs) treatment of a vector$\times$vector contact interaction (CI). The results found for the meson masses and the weak decay constants, for the spin-spin combinations studied, are in fairly good agreement with experimental data and earlier model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations (BSEs) involving sophisticated interaction kernels. The charge radius of ${\eta }_c(1S)$ is consistent with the results from refined SDE studies and lattice Quantum Chromodynamics (QCD).

   hep-phnucl-thPRD(2015)·58 citations
10. 10*

    Diphoton excess in phenomenological spin-2 resonance scenarios

    Antony Martini🇧🇪 · Kentarou Mawatari🇫🇷 · Dipan Sengupta🇫🇷

    We provide a possible explanation of a 750 GeV diphoton excess recently reported by both the ATLAS and CMS collaborations in the context of phenomenological spin-2 resonance scenarios, where the independent effective couplings of the resonance with gluons, quarks and photons are considered. We find a parameter region where the excess can be accounted for without conflicting with dijet constraints. We also show that the kinematical distributions might help to determine the couplings to gluons and quarks.

    hep-phPRD(2016)·34 citations
11. 11*

    Phase diagram and nucleation in the Polyakov-loop-extended Quark-Meson truncation of QCD with the unquenched Polyakov-loop potential

    Rainer Stiele🇫🇷 · Juergen Schaffner-Bielich🇩🇪

    Unquenching of the Polyakov-loop potential showed to be an important improvement for the description of the phase structure and thermodynamics of strongly-interacting matter at zero quark chemical potentials with Polyakov-loop extended chiral models. This work constitutes the first application of the quark backreaction on the Polyakov-loop potential at nonzero density. The observation is that it links the chiral and deconfinement phase transition also at small temperatures and large quark chemical potentials. The build up of the surface tension in the Polyakov-loop extended Quark-Meson model is explored by investigating the two and 2+1-flavour Quark-Meson model and analysing the impact of the Polyakov-loop extension. In general, the order of magnitude of the surface tension is given by the chiral phase transition. The coupling of the chiral and deconfinement transition with the unquenched Polyakov-loop potential leads to the fact that the Polyakov-loop contributes at all temperatures.

    hep-phnucl-thPRD(2016)·32 citations
12. 12*

    Generalised unitarity for dimensionally regulated amplitudes within FDF

    William J. Torres Bobadilla🇮🇹

    We review the Four-Dimensional-Formulation variant of the Four-Dimensional-Helicity scheme, by showing two applications of this regularisation scheme. The first one is the computation of one-loop helicity amplitudes, for which we present preliminary results for the analytic expressions of the one-loop Higgs plus five- gluon amplitudes. In the second part, we study the Colour-Kinematics duality for off-shell diagrams in gauge theories coupled to matter, showing in a diagrammatic way that the Jacobi relations for the kinematic numerators of off-shell diagrams, built with Feynman rules in axial gauge, reduce to definite set of violating terms due to the contributions of sub-graphs only.

    hep-phhep-thPoS(2016)·5 citations
13. 13*

    Effects of Sfermion Mixing induced by RGE in the CMSSM

    Mario E. Gómez🇪🇸 · Sven Heinemeyer🇪🇸 · Muhammad Rehman🇪🇸

    Even within the Constrained Minimal Supersymmetric Standard Model (CMSSM) it is possible to induce sfermion flavor mixing through the Renormalization Group Equations (RGE) when the full structure of the Yukawa couplings is considered. We analyse the impact of including those effects on the accurate computation of $B$-physics observables, electroweak precision observables (EWPO) and the Higgs boson mass predictions.

    hep-phFrascati Phys.Ser.(2016)·0 citations
14. 14*

    Symmetry preserving truncations of the gap and Bethe-Salpeter equations

    Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Joannis Papavassiliou🇪🇸 · Si-Xue Qin🇺🇸 · Craig D. Roberts🇺🇸

    Ward-Green-Takahashi (WGT) identities play a crucial role in hadron physics, e.g. imposing stringent relationships between the kernels of the one- and two-body problems, which must be preserved in any veracious treatment of mesons as bound-states. In this connection, one may view the dressed gluon-quark vertex, ${\Gamma }_{\mu }^a$, as fundamental. We use a novel representation of ${\Gamma }_{\mu }^a$, in terms of the gluon-quark scattering matrix, to develop a method capable of elucidating the unique quark-antiquark Bethe-Salpeter kernel, $K$, that is symmetry-consistent with a given quark gap equation. A strength of the scheme is its ability to expose and capitalise on graphic symmetries within the kernels. This is displayed in an analysis that reveals the origin of $H$-diagrams in $K$, which are two-particle-irreducible contributions, generated as two-loop diagrams involving the three-gluon vertex, that cannot be absorbed as a dressing of ${\Gamma }_{\mu }^a$ in a Bethe-Salpeter kernel nor expressed as a member of the class of crossed-box diagrams. Thus, there are no general circumstances under which the WGT identities essential for a valid description of mesons can be preserved by a Bethe-Salpeter kernel obtained simply by dressing both gluon-quark vertices in a ladder-like truncation; and, moreover, adding any number of similarly-dressed crossed-box diagrams cannot improve the situation.

    ↳ nucl-thhep-phPRD(2016)·119 citations
15. 15*

    Sound Speed of Primordial Fluctuations in Supergravity Inflation

    Alexander Hetz🇨🇱 · Gonzalo A. Palma🇨🇱

    We study the realization of slow-roll inflation in $\mathcal{N}=1$ supergravities where inflation is the result of the evolution of a single chiral field. When there is only one flat direction in field space, it is possible to derive a single-field effective field theory parametrized by the sound speed $c_s$ at which curvature perturbations propagate during inflation. The value of $c_s$ is determined by the rate of bend of the inflationary path resulting from the shape of the $F$-term potential. We show that $c_s$ must respect an inequality that involves the curvature tensor of the Kahler manifold underlying supergravity, and the ratio $M/H$ between the mass $M$ of fluctuations ortogonal to the inflationary path, and the Hubble expansion rate $H$. This inequality provides a powerful link between observational constraints on primordial non-Gaussianity and information about the $\mathcal{N}=1$ supergravity responsible for inflation. In particular, the inequality does not allow for suppressed values of $c_s$ (values smaller than $c_s\sim 0.4$) unless (a) the ratio $M/H$ is of order 1 or smaller, and (b) the fluctuations of mass $M$ affect the propagation of curvature perturbations by inducing on them a nonlinear dispersion relation during horizon crossing. Therefore, if large non-Gaussianity is observed, supergravity models of inflation would be severely constrained.

    ↳ hep-thastro-ph.COhep-phPRL(2016)·62 citations
16. 16*

    Testing CCQE and 2p2h models in the NEUT neutrino interaction generator with published datasets from the MiniBooNE and MINERvA experiments

    C. Wilkinson🇬🇧 · R. Terri🇬🇧 · C. Andreopoulos🇬🇧 · A. Bercellie🇺🇸 · C. Bronner🇯🇵 · S. Cartwright🇬🇧 · P. de Perio🇨🇦 · J. Dobson🇬🇧 · K. Duffy🇬🇧 · A.P. Furmanski🇬🇧 · L. Haegel🇨🇭 · Y. Hayato🇯🇵 and 17 other authors

    The MiniBooNE large axial mass anomaly has prompted a great deal of theoretical work on sophisticated Charged Current Quasi-Elastic (CCQE) neutrino interaction models in recent years. As the dominant interaction mode at T2K energies, and the signal process in oscillation analyses, it is important for the T2K experiment to include realistic CCQE cross section uncertainties in T2K analyses. To this end, T2K's Neutrino Interaction Working Group has implemented a number of recent models in NEUT, T2K's primary neutrino interaction event generator. In this paper, we give an overview of the models implemented, and present fits to published muon neutrino and muon antineutrino CCQE cross section measurements from the MiniBooNE and MINERvA experiments. The results of the fits are used to select a default cross section model for future T2K analyses, and to constrain the cross section uncertainties of the model. We find a model consisting of a modified relativistic Fermi gas model and multinucleon interactions most consistently describes the available data.

    ↳ hep-exhep-phnucl-exPRD(2016)·71 citations
17. 17*

    Specific Heat of Matter Formed in Relativistic Nuclear Collisions

    Sumit Basu🇮🇳 · Sandeep Chatterjee🇮🇳 · Rupa Chatterjee🇮🇳 · Tapan K. Nayak🇮🇳 · Basanta K. Nandi🇮🇳

    We report the excitation energy dependence of specific heat (\cv) of hadronic matter at freeze-out in Au+Au and Cu+Cu collisions at the Relativistic Heavy Ion Collider energies by analyzing the published data on event-by-event mean transverse momentum (\meanpt) distributions. The \meanpt~distributions in finite \pt~ranges are converted to distributions of effective temperatures, and dynamical fluctuations in temperature are extracted by subtracting widths of the corresponding mixed event distributions. The heat capacity per particle at the kinetic freeze-out surface is presented as a function of collision energy, which shows a sharp rise in \cv~below \sNN~=~62.4~GeV. We employ the Hadron Resonance Gas (HRG) model to estimate \cv~at the chemical and kinetic freeze-out surfaces. The experimental results are compared to the HRG and other theoretical model calculations. HRG results show good agreement with data. Model predictions for \cv~at the Large Hadron Collider energy are presented.

    ↳ nucl-exhep-phnucl-thPRC(2016)·37 citations
18. 18*

    Probing the hadron-quark mixed phase at high isospin and baryon density - Sensitive observables

    Massimo Di Toro🇮🇹 · Maria Colonna🇮🇹 · Vincenzo Greco🇮🇹 · Guo-Yun Shao🇨🇳

    We discuss the isospin effect on the possible phase transition from hadronic to quark matter at high baryon density and finite temperatures. The two-Equation of State (Two-EoS) model is adopted to describe the hadron-quark phase transition in dense matter formed in heavy-ion collisions. For the hadron sector we use Relativistic Mean Field (RMF) effective models, already tested on heavy ion collision (HIC). For the quark phase we consider various effective models, the MIT-Bag static picture, the Nambu--Jona-Lasinio (NJL) approach with chiral dynamics and finally the NJL coupled to the Polyakov-loop field (PNJL), which includes both chiral and (de)confinement dynamics. The idea is to extract mixed phase properties which appear robust with respect to the model differences. In particular we focus on the phase transitions of isospin asymmetric matter, with two main results: i) an earlier transition to a mixed hadron-quark phase, at lower baryon density/chemical potential with respect to symmetric matter; ii) an "Isospin Distillation" to the quark component of the mixed phase, with predicted effects on the final hadron production. Possible observation signals are suggested to probe in heavy-ion collision experiments at intermediate energies, in the range of the NICA program.

    ↳ nucl-thhep-phEPJA(2016)·3 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.