Thu·Aug 11, 2016Thursday·August 11, 2016

1. 01*

   Drell-Yan process in $pA$ collisions: the exact treatment of coherence effects

   Victor P. Goncalves🇧🇷 · Michal Krelina🇨🇿 · Jan Nemchik🇨🇿 · Roman Pasechnik🇸🇪

   In this work, we investigate production of Drell-Yan (DY) pairs in proton-nucleus collisions in kinematic regions where the corresponding coherence length does not exceed the nuclear radius, $R_A$, and the quantum coherence effects should be treated with a special care. The results for the nucleus-to-nucleon production ratio available in the literature so far are usually based on the assumption of a very long coherence length (LCL) $l_c\gg R_A$. Since the onset of coherence effects is controlled by the coherence length $l_c$, we estimated its magnitude in various kinematic regions of the DY process and found that the LCL approximation should not be used at small and medium c.m. collision energies ($\sqrt{s}\lesssim 200$ GeV) as well as at large dilepton invariant masses. In order to obtain realistic predictions, we computed for the first time the DY cross section using the generalised color dipole approach based on the rigorous Green function formalism, which naturally incorporates the color transparency and quantum coherence effects and hence allows to estimate the nuclear shadowing with no restrictions on the CL. In addition to the shadowing effect, we studied a complementary effect of initial state interactions (ISI) that causes an additional suppression at large values of the Feynman variable. Numerical results for the nuclear modification factor accounting for the ISI effect and the finite $l_c$ are compared to the data available from the fixed-target FNAL measurements and a good agreement has been found. Besides, we present new predictions for the nuclear suppression as a function of dilepton rapidity and invariant mass in the kinematic regions that can be probed by the RHIC collider as well as by the planned AFTER@LHC and LHCb fixed-target experiments.

   hep-phPRD(2016)·7 citations
2. 02*

   Detection of sub-GeV Dark Matter and Solar Neutrinos via Chemical-Bond Breaking

   Rouven Essig🇺🇸 · Jeremy Mardon🇺🇸 · Oren Slone🇮🇱 · Tomer Volansky🇮🇱

   We explore a new low-threshold direct-detection concept for dark matter, based on the breaking of chemical bonds between atoms. This includes the dissociation of molecules and the creation of defects in a lattice. With thresholds of a few to 10's of eV, such an experiment could probe the nuclear couplings of dark matter particles as light as a few MeV. We calculate the expected rates for dark matter to break apart diatomic molecules, which we take as a case study for more general systems. We briefly mention ideas for how chemical-bond breaking might be detected in practice. We also discuss the possibility of detecting solar neutrinos, including pp neutrinos, with this experimental concept. With an event rate of $\mathcal{O}$(0.1/kg-year), large exposures are required, but measuring low-energy solar neutrinos would provide a crucial test of the solar model.

   hep-phastro-ph.COhep-exPRD(2017)·93 citations
3. 03*

   Search for Lorentz Violation in km${}^3$-Scale Neutrino Telescopes

   C.A. Argüelles🇺🇸 · G.H. Collin🇺🇸 · J.M. Conrad🇺🇸 · T. Katori🇬🇧 · A. Kheirandish🇺🇸

   Kilometer${}^3$-scale neutrino detectors such as IceCube, ANTARES, and the proposed Km3Net neutrino observatory in the Mediterranean have measured, and will continue to characterize, the atmospheric neutrino spectrum above 1 TeV. Such precise measurements enable us to probe new neutrino physics, in particular, those that arise from Lorentz violation. In this paper, we first relate the effective new physics hamiltonian terms with the Lorentz violating literature. Second, we calculate the oscillation probability formulas for the two-level ${\nu }_{\mu }-{\nu }_{\tau }$ sector. Finally, we comment on some of the challenges and outlook for this analysis.

   hep-ph3 citations
4. 04*

   Distributions for neutral Higgs production in the NMSSM

   Stefan Liebler🇩🇪 · Hendrik Mantler🇩🇪 · Marius Wiesemann🇨🇭

   A novel computation of the fully-differential cross section for neutral Higgs-boson production through gluon fusion in the CP-conserving NMSSM is presented. Based on the calculation of NLO corrections to the total cross section [1], we implemented the NMSSM amplitudes in three codes, applying different resummation techniques: analytic transverse-momentum resummation at NLO+NLL, and two fully-differential NLO+PS Monte-Carlo approaches using the MC@NLO and POWHEG matching procedures, respectively. We study phenomenological predictions for distributions in the NMSSM with a special emphasis on the Higgs transverse-momentum spectrum. Reasonable agreement among the various approaches is found, once well-motivated choices for the unphysical matching scales and the determination of the related uncertainties are made.

   hep-ph9 citations
5. 05*

   Revisiting the b1 pi and rho pi decay modes of the 1-+ light hybrid state with light-cone QCD sum rules

   Zhuo-Ran Huang🇨🇳 · Hong Ying Jin🇨🇳 · T.G. Steele🇨🇦 · Zhu Feng Zhang🇨🇳

   We study the $\rho \pi$ and $b_1\pi$ decay modes of the $1^{-+}$ light hybrid state within the framework of light-cone QCD sum rules. We use both the tensor current $\bar{\psi }{\sigma }_{\mu \nu }\psi$ and the derivative current $\bar{\psi }{\overleftrightarrow{D}}_{\mu }{\gamma }_5\psi$ as interpolating currents to calculate the partial decay width of the $b_1\pi$ decay mode. Comparing the sum rules obtained by using different currents, we obtain $\Gamma ({\pi }_1\to b_1\pi )$ = 8--23, 32--86 and 52--151\,MeV for $m_{1^{-+}}$ = 1.6, 1.8 and 2.0\,GeV respectively, which favour the results from the flux tube models and lattice simulations. We also use the tensor current to study the $\rho \pi$ decay mode, and although an extended stability criterion is needed, our results suggest a small partial decay width.

   hep-phPRD(2016)·21 citations
6. 06*

   SUSY Dark Matter in Universal and Nonuniversal Gaugino Mass Models

   D. P. Roy🇮🇳

   We review the phenomenology of SUSY dark matter in various versions of MSSM, with universal and nonuniversal gaugino masses at the GUT scale. We start with the universal case (CMSSM), where the cosmologically compatible dark matter relic density is achieved only over some narrow regions of parameter space, involving some fine-tuning. Moreover, most of these regions are seriously challenged by the constraints from collider and direct dark matter detection experiments. Then we consider some simple and predictive nonuniversal gaugino mass models, based on SU(5) GUT. Several of these models offer viable SUSY dark matter candidates, which are compatible with the cosmic dark matter relic density and the above mentioned experimental constraints. They can be probed at the present and future collider and dark matter search experiments. Finally, we consider the nonuniversal gaugino mass model arising from anomaly mediated SUSY breaking. In this case the cosmologically compatible dark matter relic density requires dark matter mass of a few TeV, which puts it beyond the scope of collider and direct dark matter detection experiments. However, it has interesting predictions for some indirect dark matter detection experiments.

   hep-phIndian J.Phys.(2017)·2 citations
7. 07*

   Simulating V+jet processes in heavy ion collisions with JEWEL

   Raghav Kunnawalkam Elayavalli🇺🇸 · Korinna Christine Zapp🇨🇭

   Processes in which a jet recoils against an electroweak boson complement studies of jet quenching in heavy ion collisions at the LHC. As the boson does not interact strongly it escapes the dense medium unmodified and thus provides a more direct access to the hard scattering kinematics than can be obtained in di-jet events. First measurements of jet modification in these processes are now available from the LHC experiments and will improve greatly with better statistics in the future. We present an extension of JEWEL to boson-jet processes. JEWEL is a dynamical framework for jet evolution in a dense background based on perturbative QCD, that is in agreement with a large variety of jet observables. We also obtain a good description of the CMS and ATLAS data for y+jet and Z+jet processes at 2.76 TeV and 5.02 TeV.

   hep-phEPJC(2016)·60 citations
8. 08*

   Chiral extrapolation of nucleon axial charge $g_A$ in effective field theory

   Hongna Li🇨🇳 · Ping Wang🇨🇳

   The extrapolation of nucleon axial charge $g_A$ is investigated within the framework of heavy baryon chiral effective field theory. The intermediate octet and decuplet baryons are included in the one loop calculation. Finite range regularization is applied to improve the convergence in the quark-mass expansion. The lattice data from three different groups are used for the extrapolation. At physical pion mass, the extrapolated $g_A$ are all smaller than the experimental value.

   hep-phhep-latCPC(2016)·5 citations
9. 09*

   Associated production of a quarkonium and a Z boson at one loop in a quark-hadron-duality approach

   Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇨🇭

   In view of the large discrepancy about the associated production of a prompt $J/\psi$ and a $Z$ boson between the ATLAS data at $\sqrt{s}=8$ TeV and theoretical predictions for Single Parton Scattering (SPS) contributions, we perform an evaluation of the corresponding cross section at one loop accuracy (Next-to-Leading Order, NLO) in a quark-hadron-duality approach, also known as the Colour-Evaporation Model (CEM). This work is motivated by (i) the extremely disparate predictions based on the existing NRQCD fits conjugated with the absence of a full NLO NRQCD computation and (ii) the fact that we believe that such an evaluation provides a likely upper limit of the SPS cross section. In addition to these theory improvements, we argue that the ATLAS estimation of the Double Parton Scattering (DPS) yield may be underestimated by a factor as large as 3 which then reduces the size of the SPS yield extracted from the ATLAS data. Our NLO SPS evaluation also allows us to set an upper limit on ${\sigma }_{\mathrm{eff}}$ driving the size of the DPS yield. Overall, the discrepancy between theory and experiment may be smaller than expected, which calls for further analyses by ATLAS and CMS, for which we provide predictions, and for full NLO computations in other models. As an interesting side product of our analysis, we have performed the first NLO computation of $d\sigma /d{P}_T$ for prompt single-$J/\psi$ production in the CEM from which we have fit the CEM non-pertubative parameter at NLO using the most recent ATLAS data.

   hep-phhep-exJHEP(2016)·50 citations
10. 10*

    Positivity of Curvature-Squared Corrections in Gravity

    Clifford Cheung🇺🇸 · Grant N. Remmen🇺🇸

    We study the Gauss-Bonnet (GB) term as the leading higher-curvature correction to pure Einstein gravity. Assuming a tree-level ultraviolet completion free of ghosts or tachyons, we prove that the GB term has a nonnegative coefficient in dimensions greater than four. Our result follows from unitarity of the spectral representation for a general ultraviolet completion of the GB term.

    ↳ hep-thgr-qchep-phPRL(2017)·128 citations
11. 11*

    Hydrodynamic Predictions for Mixed Harmonic Correlations in 200 GeV Au+Au Collisions

    Fernando G. Gardim🇧🇷 · Frederique Grassi🇧🇷 · Matthew Luzum🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸

    Recent measurements at the LHC involve the correlation of different azimuthal flow harmonics $v_n$. These new observables add constraints to theoretical models and probe aspects of the system that are independent of the traditional single-harmonic measurements such as 2- and multi-particle cumulants $v_n\{m\}$. Many of these new observables have not yet been measured at RHIC, leaving an opportunity to make predictions as a test of models across energies. We make predictions using NeXSPheRIO, a hydrodynamical model which has accurately reproduced a large set of single-harmonic correlations in a large range of transverse momenta and centralities at RHIC. Our predictions thus provide an important baseline for comparison to correlations of flow harmonics, which contain non-trivial information about the initial state as well as QGP transport properties. We also point out significant biases that can appear when using wide centrality bins and non-trivial event weighting, necessitating care in performing experimental analyses and in comparing theoretical calculations to these measurements.

    ↳ nucl-thhep-phPRC(2017)·52 citations
12. 12*

    Radial excitations of current-carrying vortices

    Betti Hartmann🇧🇷 · Florent Michel🇫🇷 · Patrick Peter🇫🇷

    We report on the existence of a new type of cosmic string solutions in the Witten model with U(1)xU(1) symmetry. These solutions are superconducting with radially excited condensates that exist for both gauge and ungauged currents. Our results suggest that these new configurations can be macroscopically stable, but microscopically unstable to radial perturbations. Nevertheless, they might have important consequences for the network evolution and particle emission. We discuss these effects and their possible signatures. We also comment on analogies with non-relativistic condensed matter systems where these solutions may be observable.

    ↳ hep-thastro-ph.COhep-phPLB(2017)·5 citations
13. 13*

    Impact of ADC non-linearities on the sensitivity to sterile keV neutrinos with a KATRIN-like experiment

    K. Dolde🇩🇪 · S. Mertens🇩🇪 · D. Radford🇺🇸 · T. Bode🇩🇪 · A. Huber🇩🇪 · M. Korzeczek🇩🇪 · T. Lasserre🇫🇷 · M. Slezak🇩🇪

    ADC non-linearities are a major systematic effect in the search for keV-scale sterile neutrinos with tritium $\beta$-decay experiments like KATRIN. They can significantly distort the spectral shape and thereby obscure the tiny kink-like signature of a sterile neutrino. In this work we demonstrate various mitigation techniques to reduce the impact of ADC non-linearities on the tritium $\beta$-decay spectrum to a level of $<$ ppm. The best results are achieved with a multi-pixel ($\ge 10^4$ pixels) detector using full waveform digitization. In this case, active-to-sterile mixing angles of the order of ${\sin }^2\theta =10^{-7}$ would be accessible from the viewpoint of ADC non-linearities. With purely peak-sensing ADCs a comparable sensitivity could be reached with highly linear ADCs, sufficient non-linearity corrections or by increasing the number of pixels to $\ge 10^5$.

    ↳ physics.ins-dethep-phNucl.Instrum.Meth.A(2017)·16 citations
14. 14*

    Harmonic Oscillators and Elementary Particles

    Y. Sobouti🇮🇷

    Two dynamical systems with same symmetry should have features in common, and as far as their shared symmetry is concerned, one may represent the other. The three light quark constituents of the hadrons, a) have an approximate flavor SU(3) symmetry, b) have an exact color SU(3) symmetry, and c) as spin 1/2 particles, have a Lorentz SO(3,1) symmetry. So does a 3D harmonic oscillator. a) Its Hamiltonian has the SU(3) symmetry, breakable if the 3 fundamental modes of oscillation are not identical. b) The 3 directions of oscillation have the permutation symmetry. This enables one to create three copies of unbreakable SU(3) symmetry for each mode of the oscillation, and mimic the color of the elementary particles. And c) The Lagrangian of the 3D oscillator has the SO(3,1) symmetry. This can be employed to accommodate the spin of the particles. In this paper we draw up a one-to-one correspondence between the eigen modes of the Poisson bracket operator of the 3D oscillator and the flavor multiplets of the particles, and between the permuted modes of the oscillator and the color and anticolor multiplets of the particles. Gluons are represented by the generators of the color SU(3) symmetry of the oscillator. Harmonic oscillators are common place objects and, wherever encountered, are analytically solvable. Elementary particles, on the other hand, are abstract entities far from one's reach. Understanding of one may help a better appreciation of the other.

    ↳ physics.gen-phhep-phhep-thJ.Phys.Comm.(2018)·1 citation

* 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.