Mon·Oct 26, 2015Monday·October 26, 2015

1. 01*

   Probing GPDs in photoproduction processes at hadron colliders

   D.Yu. Ivanov🇷🇺 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · J. Wagner🇵🇱

   Generalized parton distributions (GPDs) enter QCD factorization theorems for hard exclusive reactions. They encode rich information about hadron partonic structure. We explore a possibility to constrain GPDs in experiments at LHC considering two different exclusive processes: the timelike Compton scattering and the photoproduction of heavy vector mesons.

   hep-phhep-exnucl-ex13 citations
2. 02*

   Equilibration, particle production, and self-energy

   D. Bodeker🇩🇪 · M. Sangel🇩🇪 · M. Wormann🇩🇪

   The discontinuity, or imaginary part of a self-energy at finite temperature is proportional to the rate at which the corresponding particles are produced when very few of them are present, and also to the rate at which their phase space density approaches the thermal one. These relations were suggested by Weldon [1], who demonstrated them for low orders in perturbation theory. Here we show that they are valid at leading order in a linear coupling of the produced particles, and to all orders in all other interactions of the hot plasma, if there is a separation of the time scales for the production and for the thermalization of the bulk of the plasma.

   hep-phhep-thPRD(2016)·36 citations
3. 03*

   Prospects for Beyond the Standard Model Physics at the Start of the LHC13 era

   Howard Baer🇺🇸

   The discovery of the Higgs boson along with the vigorous confirmation of the SM coupled with non-appearance of new (SUSY) particles has led to an apparent naturalness crisis. We argue the crisis stems from overestimates of finetuning. A proper evaluation of naturalness in SUSY leads to light higgsinos with mass mu~ 100-300 GeV while other sparticles may inhabit the multi-TeV range at little cost to naturalness. Special signatures like dilepton mass edges in gluino pair events and same-sign dibosons from wino pairs might occur at LHC13. An ILC with \sqrt{s}>2 mu would make the definitive test of naturalness in the MSSM. Naturalness in the QCD sector requires the axion leading to mixed axion-WIMP dark matter. There appears a deep connection between electroweak naturalness and a DFSZ-like SUSY axion sector which gives rise to the mu~ f_a^2/M_P parameter. Ultimately we expect detection of a higgsino-like WIMP at ton-scale DM detectors and detection of a DFSZ-type axion at ADMX.

   hep-phPoS(2015)·0 citations
4. 04*

   On the Computation of Form Factors in Massless QCD with Finite Master Integrals

   Andreas von Manteuffel🇩🇪 · Erik Panzer🇬🇧 · Robert M. Schabinger🇮🇪

   We present the bare one-, two-, and three-loop form factors in massless Quantum Chromodynamics as linear combinations of finite master integrals. Using symbolic integration, we compute their $ϵ$ expansions and thereby reproduce all known results with an independent method. Remarkably, in our finite basis, only integrals with a less-than-maximal number of propagators contribute to the cusp anomalous dimensions. We report on indications of this phenomenon at four loops, including the result for a finite, irreducible, twelve-propagator form factor integral. Together with this article, we provide our automated software setup for the computation of finite master integrals.

   hep-phhep-thPRD(2016)·71 citations
5. 05*

   Transverse Spin Structure of the Nucleon

   Matthias Grosse Perdekamp🇺🇸 · Feng Yuan🇺🇸

   We review the current status and future perspectives of theory and experiments of transverse spin phenomena in high-energy scattering processes off nucleon targets and related issues in nucleon structure and QCD. Systematic exploration of transverse spin effects requires measurements in polarized deep-inelastic scattering, polarized pp collisions, and e+e- annihilations. Sophisticated QCD-based techniques are also needed to analyze the experimental data sets.

   hep-phhep-exnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2015)·47 citations
6. 06*

   Production of doubly heavy-flavored hadrons at $e^{+}{e}^{-}$ colliders

   Xu-Chang Zheng🇨🇳 · Chao-Hsi Chang🇨🇳 · Zan Pan🇨🇳

   Production of the doubly heavy-flavored hadrons ($B_c$ meson, doubly heavy baryons ${\Xi }_{cc}$, ${\Xi }_{bc}$, ${\Xi }_{bb}$, their excited states and antiparticles of them as well) at $e^{+}{e}^{-}$ colliders is investigated under two different approaches: $LO$ (leading order QCD complete calculation) and $LL$ (leading logarithm fragmentation calculation). The results for the production obtained by the approaches $LO$ and $LL$, including the angle distributions of the produced hadrons with unpolarized and polarized incoming beams, the behaviors on the energy fraction of the produced doubly heavy hadron and comparisons between the two approaches' results, are presented in terms of tables and figures. Thus characteristics of the production and uncertainties of the approaches are shown precisely, and it is concluded that only if the colliders run at the eneries around $Z$-pole (which may be called as $Z$-factories) and additionally the luminosity of the colliders is as high as possible then to study the doubly heavy hadrons thoroughly is accessible.

   hep-phPRD(2016)·47 citations
7. 07*

   Kinetic mixing effect in the 3-3-1-1 model

   P. V. Dong🇻🇳 · D. T. Si🇻🇳

   We show that the mixing effect of the neutral gauge bosons in the 3-3-1-1 model comes from two sources. The first one is due to the 3-3-1-1 gauge symmetry breaking as usual, whereas the second one results from the kinetic mixing between the gauge bosons of U(1)_X and U(1)_N groups, which are used to determine the electric charge and baryon minus lepton numbers, respectively. Such mixings modify the \rho-parameter and the known couplings of Z with fermions. The constraints that arise from flavor-changing neutral currents due to the gauge boson mixings and non-universal fermion generations are also given.

   hep-phPRD(2016)·19 citations
8. 08*

   The Super-Natural Supersymmetry and Its Classic Example: M-Theory Inspired NMSSM

   Tianjun Li🇨🇳 · Shabbar Raza🇨🇳 · Xiao-Chuan Wang🇨🇳

   We briefly review the super-natural supersymmetry (SUSY), which provides a most promising solution to the SUSY electroweak fine-tuning problem. In particular, we address its subtle issues as well. Unlike the Minimal Supersymmetric Standard model (MSSM), the Next to MSSM (NMSSM) can be scale invariant and has no mass parameter in its Lagrangian before SUSY and gauge symmetry breakings. Therefore, the NMSSM is a perfect framework for super-natural SUSY. To give the SUSY breaking soft mass to the singlet, we consider the moduli and dilaton dominant SUSY breaking scenarios in M-theory on $S^1/Z_2$. In these scenarios, SUSY is broken by one and only one $F$-term of moduli or dilaton, and the SUSY breaking soft terms can be determined via the Kähler potential and superpotential from Calabi-Yau compactification of M-theory on $S^1/Z_2$. Thus, as predicted by super-natural SUSY, the SUSY electroweak fine-tuning measure is of unity order. In the moduli dominant SUSY breaking scenario, the right-handed sleptons are relatively light around 1 TeV, stau can be even as light as 580 GeV and degenerate with the lightest neutralino, chargino masses are larger than 1 TeV, the light stop masses are around 2 TeV or larger, the first two-generation squark masses are about 3 TeV or larger, and gluinos are heavier than squarks. In the dilaton dominant SUSY breaking scenario, the qualitative picture remain the same but we have heavier spectra as compared to moduli dominant SUSY breaking scenario. In addition to it, we have Higgs $H_2/A_1$-resonance solutions for dark matter (DM). In both scenarios, the minimal value of DM relic density is about 0.2. To obtain the observed DM relic density, we can consider the dilution effect from supercritical string cosmology or introduce the axino as the lightest supersymmetric particle.

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

   Diphoton isolation studies

   Leandro Cieri🇮🇹

   We consider the effects of the photon isolation on the production of a pair of photons in hadron collisions. We study in detail advantages and disadvantages of the standard and smooth cone isolation criteria, concerning the theory and the experiment. We put special interest in those kinematic configurations related to recent Higgs boson studies and searches, and finally we show the set of isolation parameters proposed by the Les Houches accord 2013, which serves as a guide to understand the comparison of the theoretical predictions with the data.

   hep-phhep-exNucl.Part.Phys.Proc.(2016)·11 citations
10. 10*

    Axion-like particle searches with sub-THz photons

    L. Capparelli🇺🇸 · G. Cavoto🇮🇹 · J. Ferretti🇮🇹 · F. Giazotto🇮🇹 · A.D. Polosa🇮🇹 · P. Spagnolo🇮🇹

    We propose a variation, based on very low energy and extremely intense photon sources, on the well established technique of Light-Shining-through-Wall (LSW) experiments for axion-like particle searches. With radiation sources at 30 GHz, we compute that present laboratory exclusion limits on axion-like particles might be improved by at least four orders of magnitude, for masses m_a <~ 0.01~meV. This could motivate research and development programs on dedicated single-photon sub-THz detectors.

    hep-phcond-mat.supr-conPhys.Dark Univ.(2016)·54 citations
11. 11*

    The longitudinal and transverse distributions of the pion wavefunction from the present experimental data on the pion-photon transition form factor

    Tao Zhong🇨🇳 · Xing-Gang Wu🇨🇳 · Tao Huang🇨🇳

    It is noted that the low-energy behavior of the pion-photon transition form factor $F_{\pi \gamma }(Q^2)$ is sensitive to the transverse distribution of the pion wavefunction, and its high-energy behavior is sensitive to the longitudinal one. Thus a careful study on $F_{\pi \gamma }(Q^2)$ can provide helpful information on the pion wavefunction precisely. In this paper, we present a combined analysis of the data on $F_{\pi \gamma }(Q^2)$ reported by the CELLO, the CLEO, the BABAR and the BELLE collaborations. It is performed by using the method of least squares. By using the combined measurements of BELLE and CLEO Collaborations, the pion wavefunction longitudinal and transverse behavior can be fixed to a certain degree, i.e. we obtain $\beta \in [0.691,0.757]\mathrm{GeV}$ and $B\in [0.00,0.235]$ for $P_{{\chi }^2}\ge 90\%$, where $\beta$ and $B$ are two parameters of a convenient pion wavefunction model whose distribution amplitude can mimic the various longitudinal behavior under proper choice of parameters. We observe that the CELLO, CLEO and BELLE data are consistent with each other, all of which prefers the asymptotic-like distribution amplitude; while the BABAR data prefers a more broad distribution amplitude, such as the CZ-like one.

    hep-phEPJC(2016)·11 citations
12. 12*

    Recent Progress in Search for Dark Sector Signatures

    M.A. Deliyergiyev🇸🇮

    Many difficulties are encountered when attempting to pinpoint a common origin for several observed astrophysical anomalies, and when assessing their tension with existing exclusion limits. These include systematic uncertainties affecting the operation of the detectors, our knowledge of their response, astrophysical uncertainties, and the broad range of particle couplings that can mediate interaction with a detector target. Particularly interesting astrophysical evidence has motivated a search for dark-photon, and focused our attention on a Hidden Valleys model with a GeV-scale dark sector that produces exciting signatures. Results from recent underground experiments are also considered. There is a `light' hidden sector (dark sector), present in many models of new physics beyond the Standard Model, which contains a colorful spectrum of new particles. Recently, it has been shown that this spectrum can give rise to unique signatures at colliders when the mass scale in the hidden sector is well below a TeV; as in Hidden Valleys, Stueckelberg extensions, and Unparticle models. These physics models produce unique signatures of collimated leptons at high energies. By studying these ephemeral particles we hope to trace the history of the Universe. Our present theories lead us to believe that there is something new just around the corner, which should be accessible at the energies made available by modern colliders.

    hep-phOpen Phys.(2016)·41 citations
13. 13*

    Evolution of gluon TMDs from small to moderate x

    Andrey Tarasov🇺🇸

    Recently we obtained an evolution equation of gluon TMDs, which addresses a problem of unification of different kinematic regimes. It describes evolution in the whole range of Bjorken $x_B$ and the whole range of transverse momentum $k_{\perp }$. In this notes I study different limits of this evolution equation and show how it yields several well-known and some previously unknown results.

    hep-phPoS(2015)·1 citation
14. 14*

    A resolution of the inclusive flavor-breaking sum rule $\tau$ $V_{us}$ puzzle

    K. Maltman🇨🇦 · R.J. Hudspith🇨🇦 · R. Lewis🇨🇦 · C.E. Wolfe🇨🇦 · J. Zanotti🇦🇺

    A combination of continuum and lattice methods is used to investigate systematic issues in the finite-energy-sum-rule determination of $V_{us}$ based on flavor-breaking combinations of hadronic $\tau$ decay data. Results for $V_{us}$ obtained using assumptions for $D>4$ OPE contributions employed in previous conventional implementations of this approach are shown to display significant unphysical dependences on the choice of sum rule weight, $w$, and upper limit, $s_0$, of the relevant experimental spectral integrals. Continuum and lattice results suggest the necessity of a new implementation of the flavor-breaking sum rule approach, in which not only $|V_{us}|$, but also $D>4$ effective condensates are fit to data. Lattice results also provide a means of quantifying the truncation error for the slowly converging $D=2$ OPE series. The new implementation is shown to produce $|V_{us}|$ results free of unphysical $s_0$- and $w$-dependences and typically $\sim 0.0020$ higher than the (unstable) results found using the conventional implementation. With preliminary new experimental results for the $K\pi$ branching fraction, the resulting $|V_{us}|$ is in excellent agreement with that obtained from $K_{\ell 3}$, and compatible within errors with expectations from three-family unitarity.

    hep-phhep-exhep-latPoS(2016)·9 citations
15. 15*

    FIESTA 4: optimized Feynman integral calculations with GPU support

    Alexander V. Smirnov🇷🇺

    This paper presents a new major release of the program FIESTA (Feynman Integral Evaluation by a Sector decomposiTion Approach). The new release is mainly aimed at optimal performance at large scales when one is increasing the number of sampling points in order to reduce the uncertainty estimates. The release now supports graphical processor units (GPU) for the numerical integration, methods to optimize cluster-usage, as well as other speed, memory, and stability improvements.

    hep-phcs.MSComput.Phys.Commun.(2016)·282 citations
16. 16*

    The Effective Strength of Gravity, the Scale of Inflation (and how KK gravitons evade the Higuchi Bound)

    Ignatios Antoniadis🇫🇷 · Subodh P. Patil🇨🇭

    For any given momentum transfer, gravitational interactions have a strength set by a characteristic scale $M_{\ast }$ inferred from amplitudes calculated in an effective theory with a strong coupling scale $M_{\ast \ast }$. These are in general different from each other and $M_{\mathrm{pl}}$, the macroscopic strength of gravity as determined by (laboratory scale) Cavendish experiments. During single field inflation, $M_{\ast }$ can differ from $M_{\mathrm{pl}}$ due to the presence of any number of (hidden) universally coupled species between laboratory and inflationary scales. Although this has no effect on dimensionless (i.e. observable) quantities measured at a fixed scale such as the amplitude and spectral properties of the CMB anisotropies, it complicates the inference of an absolute scale of inflation given any detection of primordial tensors. In this note we review and elaborate upon these facts and address concerns raised in a recent paper.

    ↳ hep-thastro-ph.COgr-qchep-ph3 citations
17. 17*

    The charmonium dissociation in an "anomalous wind"

    Andrey V. Sadofyev🇺🇸 · Yi Yin🇺🇸

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and {\it qualitative} difference between anomalous effects on the charmonium color screening length which are {\it model-dependent} and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.

    ↳ hep-thhep-phJHEP(2016)·45 citations
18. 18*

    Testing the importance of collective correlations in neutrinoless $\beta \beta$ decay

    J. Menéndez🇯🇵 · N. Hinohara🇺🇸 · J. Engel🇺🇸 · G. Martínez-Pinedo🇩🇪 · T. R. Rodríguez🇪🇸

    We investigate the extent to which theories of collective motion can capture the physics that determines the nuclear matrix elements governing neutrinoless double-beta decay. To that end we calculate the matrix elements for a series of isotopes in the full $pf$ shell, omitting no spin-orbit partners. With the inclusion of isoscalar pairing, a separable collective Hamiltonian that is derived from the shell model effective interaction reproduces the full shell-model matrix elements with good accuracy. A version of the generator coordinate method that includes the isoscalar pairing amplitude as a coordinate also reproduces the shell model results well, an encouraging result for theories of collective motion, which can include more single-particle orbitals than the shell model. We briefly examine heavier nuclei relevant for experimental double-beta decay searches, in which shell-model calculations with all spin-orbit partners are not feasible; our estimates suggest that isoscalar pairing also plays a significant role in these nuclei, though one we are less able to quantify precisely.

    ↳ nucl-thhep-phnucl-exPRC(2016)·49 citations
19. 19*

    Notes on shear viscosity bound violation in anisotropic models

    Xian-Hui Ge🇨🇳

    The shear viscosity bound violation in Einstein gravity for anisotropic black branes is discussed, with the aim of constraining the deviation of the shear viscosity-entropy density ratio from the shear viscosity bound using causality and thermodynamics analysis. The results show that no stringent constraints can be imposed. The diffusion bound in anisotropic phases is also studied. Ultimately, it is concluded that shear viscosity violation always occurs in cases where the equation of motion of the metric fluctuations cannot be written in a form identical to that of the minimally coupled massless scalar fields.

    ↳ hep-thgr-qchep-phSCPMA(2016)·12 citations
20. 20*

    Interplay between Mach cone and radial expansion and its signal in $\gamma$-jet events

    Yasuki Tachibana🇯🇵 · Tetsufumi Hirano🇯🇵

    We study the hydrodynamic response to jet quenching in expanding quark-gluon plasma (QGP) and its signal in the resulting particle distribution. The ideal hydrodynamic simulations of the $\gamma$-jet events in heavy-ion collisions are performed in a full (3 + 1)-dimensional setup. The jet-induced Mach cone and the radial expansion of the background mutually push and distort each other. As a result, the particle emission is suppressed in the direction in which the radial flow is pushed back by the Mach cone when the jet path is an off-central one. This is the direct signal of hydrodynamic response to the jetand, moreover, includes information about the jet path in the expanding QGP fluid.

    ↳ nucl-thhep-phnucl-exPRC(2016)·39 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.