Fri·Feb 24, 2017Friday·February 24, 2017

1. 01*

   Probing the top-quark width using the charge identification of $b$ jets

   Pier Paolo Giardino🇺🇸 · Cen Zhang🇺🇸

   We propose a new method for measuring the top-quark width based on the on-/off-shell ratio of $b$-charge asymmetry in $pp\to Wbj$ production at the LHC. The charge asymmetry removes virtually all backgrounds and related uncertainties, while remaining systematic and theoretical uncertainties can be taken under control by the ratio of cross sections. Limited only by statistical error, in an optimistic scenario, we find that our approach leads to good precision at high integrated luminosity, at a few hundred MeV assuming 300-3000 fb${}^{-1}$ at the LHC. The approach directly probes the total width, in such a way that model-dependence can be minimized. It is complementary to existing cross section measurements which always leave a degeneracy between the total rate and the branching ratio, and provides valuable information about the properties of the top quark. The proposal opens up new opportunities for precision top measurements using a $b$-charge identification algorithm.

   hep-phhep-exPRD(2017)·16 citations
2. 02*

   Photoproduction of doubly heavy baryon at the LHeC

   Bi Huan-Yu🇨🇳 · Zhang Ren-You🇨🇳 · Xing-Gang Wu🇨🇳 · Ma Wen-Gan🇨🇳 · Li Xiao-Zhou🇨🇳 · Samuel Owusu🇨🇳

   The photoproduction of doubly heavy baryon, ${\Xi }_{cc}$, ${\Xi }_{bc}$ and ${\Xi }_{bb}$, is predicted within the nonrelativistic QCD at the Large Hadron Electron Collider (LHeC). The ${\Xi }_{Q{Q}^{\prime }}$ production via the photon-gluon fusing channel $\gamma +g\to ⟨Q{Q}^{\prime }⟩[n]+\bar{Q}+\overline{Q^{\prime }}$ and the extrinsic heavy quark channel $\gamma +Q\to ⟨Q{Q}^{\prime }⟩[n]+\overline{Q^{\prime }}$ have been considered, where $Q$ or $Q^{\prime }$ stand for heavy $c$ or $b$ quark and $⟨Q{Q}^{\prime }⟩[n]$ stands for a $Q{Q}^{\prime }$ diquark with given spin- and color- configurations $[n]$. The diquark shall fragmentate into ${\Xi }_{Q{Q}^{\prime }}$ baryon with high probability. For ${\Xi }_{cc}$ and ${\Xi }_{bb}$ production, $[n]$ equals ${[}^1{S}_0{]}_{\text{6}}$ (in configurations spin-singlet ${}^1{S}_0$-wave and color-sextuplet $\text{6}$) or ${[}^3{S}_1{]}_{\bar{\text{3}}}$ (in configurations spin-triplet ${}^3{S}_1$-wave and color-antitriplet $\bar{\text{3}}$) and for ${\Xi }_{bc}$ production, $[n]$ equals ${[}^1{S}_0{]}_{\bar{\text{3}}}$, ${[}^1{S}_0{]}_{\text{6}}$, ${[}^3{S}_1{]}_{\bar{\text{3}}}$ or ${[}^3{S}_1{]}_{\text{6}}$. A detailed comparison of those channels and configurations on total and differential cross sections, together with their uncertainties, is presented. We find the dominate contributions for ${\Xi }_{Q{Q}^{\prime }}$ production are from extrinsic heavy quark channel and for ${[}^3{S}_1{]}_{\bar{\text{3}}}$ configuration; While other diquark states can also provide sizable contributions to the ${\Xi }_{Q{Q}^{\prime }}$ production. As a combination of all the mentioned channels and configurations and by taking $m_c=1.80\pm 0.10$ GeV and $m_b=5.1\pm 0.20$ GeV, we observe that $(6.70_{-1.10}^{+1.40})\times 10^3$ ${\Xi }_{bb}$, $(8.81_{-2.20}^{+3.08})\times 10^6$ ${\Xi }_{cc}$ and $(4.63_{-0.92}^{+1.21})\times 10^5$ ${\Xi }_{bc}$ events can be generated at the LHeC in one operation year.

   hep-phPRD(2017)·42 citations
3. 03*

   Modified Tsallis and Weibull distributions for multiplicities in e+e- collisions

   S. Sharma🇮🇳 · M. Kaur🇮🇳 · S. Thakur🇮🇳

   Multiplicity distributions of charged particles produced in the e^{+}e^{-} collisions at energies ranging from 14 to 91 GeV are studied using Tsallis q-statistics and the recently proposed Weibull distribution functions, in both restricted rapidity windows as well as in full phase space. It is shown that Tsallis $q$-statistics explains the data excellently in all rapidity ranges while the Weibull distribution fails to reproduce the data in full phase space. Modifications to the distributions are proposed to establish manifold improvements in the fitting of the data.

   hep-phPRD(2017)·4 citations
4. 04*

   Cross Section Prediction for Inclusive Production of Z Boson in $pp$ Collisions at $\sqrt{s}$$=14$ TeV: A Study of Systematic Uncertainty Due to Scale Dependence

   Hasan Ogul🇹🇷 · Kamuran Dilsiz🇹🇷

   Prediction of $Z\to l^{+}{l}^{-}$ production cross section (where $l^{\pm }=e^{\pm },{\mu }^{\pm }$) in proton-proton collisions at $\sqrt{s}$=14 TeV is estimated up to next-to-next-to-leading order (NNLO) in perturbative QCD including next-to-leading order (NLO) electroweak (EW) corrections. The total inclusive Z boson production cross section times leptonic branching ratio, within the invariant mass window $66<m_{ll}<116$ GeV, is predicted using NNLO HERAPDF2.0 at NNLO QCD and NLO EW as ${\sigma }_Z^{Tot}$= 2111.69${}_{-26.92}^{+26.31}$ (PDF) $\pm 11$ (${\alpha }_s$) $\pm$17 (scale) ${}_{-30.98}^{+57.41}$ (parameterization and model). Theoretical prediction of the fiducial cross section is further computed with the latest modern PDF models (CT14, MMHT2014, NNPDF3.0, HERAPDF2.0 and ABM12) at NNLO for QCD and NLO for EW. The central values of the predictions are based on DYNNLO 1.5 program and the uncertainties are extracted using FEWZ 3.1 program. In addition, the cross section is also calculated as functions of ${\mu }_R$ and ${\mu }_F$ scales. The choice of ${\mu }_R$ and ${\mu }_F$ for scale variation uncertainty is further discussed in details.

   hep-phAdv.High Energy Phys.(2017)·13 citations
5. 05*

   Direct searches of Type III seesaw triplet fermions at high energy $e^{+}{e}^{-}$ collider

   Deepanjali Goswami🇮🇳 · P. Poulose🇮🇳

   The signatures of heavy fermionic triplets ($\Sigma$) arising in scenarios like Type III seesaw model are probed through their direct production and subsequent decay at high energy electron-positron collider. Unlike the case of LHC, the production process has strong dependence on the mixing parameter ($V_{e,\mu }$), making the leptonic collider unique to probe such mixing. We have established that with suitably chosen kinematic cuts, a 1 TeV $e^{+}{e}^{-}$ collider could probe the presence of $\Sigma$ of mass in the range of 500 GeV having $V_e=0.05$ with a few inverse femto barn luminosity through single production. The cross section is found to be not sufficient to probe the case of triplet-muon mixing through single triplet production. On the other hand, the pair production considered at 2 TeV centre of mass energy is capable of probing both the mixing scenarios efficiently. Studying the mass reach, presence of charged fermionic triplets upto a mass of about 980 GeV could be established at $3\sigma$ level through single production at a 1 TeV $e^{+}{e}^{-}$ collider with moderate luminosity of 100 fb${}^{-1}$, assuming $V_e=0.05$ . The pair production case requires larger luminosity, as the cross section is smaller in this case. With an integrated luminosity of 300 fb${}^{-1}$, the mass reach in this case is close to 1 TeV with triplet-muon mixing, while it is slightly lower at about 950 GeV in the case of $V_{\mu }=0.05$.

   hep-phEPJC(2018)·15 citations
6. 06*

   Role of a triangle singularity in the $\pi \Delta$ decay of the $N(1700)(3/2^{-})$

   L. Roca🇪🇸 · E. Oset🇪🇸

   We show the important role played by the $\pi \Delta (1232)$ channel in the build up of the $N(1700)(3/2^{-})$ resonance due to the non-trivial enhancement produced by a singularity of a triangular loop. The $N(1700)$ is one of the dynamically generated resonances produced by the coupled channel vector-baryon interaction. The $\pi \Delta$ channel was neglected in previous works but we show that it has to be incorporated into the coupled channel formalism due to an enhancement produced by a singularity in the triangular loop with $\rho$, nucleon and $\pi$ as internal loop lines and $\pi$ and $\Delta$ as external ones. The enhancement is of non-resonant origin but it contributes to the dynamical generation of the $N(1700)$ resonance due to the non-linear dynamics involved in the coupled channel mechanisms. We obtain an important increase of the total width of the $N(1700)$ resonance when the $\pi \Delta$ channel is included and provide predictions for the partial widths of the $N(1700)$ decays into $VB$ and $\pi \Delta$.

   hep-phPRC(2017)·29 citations
7. 07*

   Effect of CP violation in the singlet-doublet dark matter model

   Tomohiro Abe🇯🇵

   We revisit the singlet-doublet dark matter model with a special emphasis on the effect of CP violation on the dark matter phenomenology. The CP violation in the dark sector induces a pseudoscalar interaction of a fermionic dark matter candidate with the SM Higgs boson. The pseudoscalar interaction helps the dark matter candidate evade the strong constraints from the dark matter direct detection experiments. We show that the model can explain the measured value of the dark matter density even if dark matter direct detection experiments do not observe any signal. We also show that the electron electric dipole moment is an important complement to the direct detection for testing this model. Its value is smaller than the current upper bound but within the reach of future experiments.

   hep-phPLB(2017)·35 citations
8. 08*

   Semi-leptonic $B$-physics anomalies: a general EFT analysis within $U(2{)}^n$ flavor symmetry

   Marzia Bordone🇨🇭 · Gino Isidori🇨🇭 · Sokratis Trifinopoulos🇨🇭

   We analyse the recent hints of Lepton Flavor Universality violations in semi-leptonic $B$ decays within a general EFT based on a $U(2{)}^n$ flavor symmetry acting on the light generations of SM fermions. We analyse in particular the consistency of these anomalies with the tight constraints on various low-energy observables in $B$ and $\tau$ physics. We show that, with a moderate fine-tuning, a consistent picture for all low-energy observables can be obtained under the additional dynamical assumption that the NP sector is coupled preferentially to third generation SM fermions. We discuss how this dynamical assumption can be implemented in general terms within the EFT, and we identify a series of observables in $\tau$ decays which could provide further evidences of this NP framework.

   hep-phPRD(2017)·62 citations
9. 09*

   Single and Double SM-like Higgs Boson Production at Future Electron-Positron Colliders in C2HDMs

   Stefania De Curtis🇮🇹 · Stefano Moretti🇬🇧 · Kei Yagyu🇮🇹 · Emine Yildirim🇬🇧

   We investigate single- and double-$h$, the discovered Standard Model (SM)-like Higgs boson, production at future $e^{+}{e}^{-}$ colliders in Composite 2-Higgs Doublet Models (C2HDMs) and Elementary 2-Higgs Doublet Models (E2HDMs) with a softly-broken $Z_2$ symmetry. We first survey their parameter spaces allowed by theoretical bounds from perturbative unitarity and vacuum stability as well as by future data at the Large Hadron Collider (LHC) with an integrated luminosity up to 3000 fb${}^{-1}$ under the assumption that no new Higgs boson is detected. We then discuss how different the cross sections can be between the two scenarios when ${\kappa }_V^{}$, the $hVV$ ($V=W^{\pm },Z$) coupling normalised to the SM value, is taken to be the same value in the both scenario We find that if ${\kappa }_V^2$ is found to be, e.g., $0.98$, then the cross sections in C2HDMs with $f$ (the compositeness scale) in the TeV region can be maximally changed to be about $-15\%$, $-18\%$, $-50\%$ and $-35\%$ for the $e^{+}{e}^{-}\to t\bar{t}h$, $e^{+}{e}^{-}\to Zhh$, $e^{+}{e}^{-}\to e^{+}{e}^{-}hh$ and $e^{+}{e}^{-}\to t\bar{t}hh$ processes, respectively, with respect to those in E2HDMs. Thus, a future electron-positron collider has the potential to discriminate between E2HDMs and C2HDMs, even when only $h$ event rates are measured.

   hep-phPRD(2017)·16 citations
10. 10*

    Anarchy and Neutrino Physics

    Jean-François Fortin🇨🇦 · Nicolas Giasson🇨🇦 · Luc Marleau🇨🇦

    The neutrino sector of a seesaw-extended Standard Model is investigated under the anarchy hypothesis. The previously derived probability density functions for neutrino masses and mixings, which characterize the type I-III seesaw ensemble of $N\times N$ complex random matrices, are used to extract information on the relevant physical parameters. For $N=2$ and $N=3$, the distributions of the light neutrino masses, as well as the mixing angles and phases, are obtained using numerical integration methods. A systematic comparison with the much simpler type II seesaw ensemble is also performed to point out the fundamental differences between the two ensembles. It is found that the type I-III seesaw ensemble is better suited to accommodate experimental data. Moreover, the results indicate a strong preference for the mass splitting associated to normal hierarchy. However, since all permutations of the singular values are found to be equally probable for a particular mass splitting, predictions regarding the hierarchy of the mass spectrum remains out of reach in the framework of anarchy.

    hep-phJHEP(2017)·12 citations
11. 11*

    Search for $t{Z}^{\prime }$ associated production induced by $tc{Z}^{\prime }$ couplings at the LHC

    Wei-Shu Hou🇹🇼 · Masaya Kohda🇹🇼 · Tanmoy Modak🇹🇼

    The $P_5^{\prime }$ and $R_K$ anomalies, recently observed by the LHCb collaboration in $B\to K^{(\ast )}$ transitions, may indicate the existence of a new $Z^{\prime }$ boson, which may arise from gauged $L_{\mu }-L_{\tau }$ symmetry. Flavor-changing neutral current $Z^{\prime }$ couplings, such as $tc{Z}^{\prime }$, can be induced by the presence of extra vector-like quarks. In this paper we study the LHC signatures of the induced right-handed $tc{Z}^{\prime }$ coupling that is inspired by, but not directly linked to, the $B\to K^{(\ast )}$ anomalies. The specific processes studied are $cg\to t{Z}^{\prime }$ and its conjugate process each followed by $Z^{\prime }\to {\mu }^{+}{\mu }^{-}$. By constructing an effective theory for the $tc{Z}^{\prime }$ coupling, we first explore model-independently the discovery potential of such a $Z^{\prime }$ at the 14 TeV LHC with 300 and 3000 fb${}^{-1}$ integrated luminosities. We then reinterpret the model-independent results within the gauged $L_{\mu }-L_{\tau }$ model. In connection with $tc{Z}^{\prime }$, the model also implies the existence of a flavor-conserving $cc{Z}^{\prime }$ coupling, which can drive the $c\bar{c}\to Z^{\prime }\to {\mu }^{+}{\mu }^{-}$ process. Our study shows that existing LHC results for dimuon resonance searches already constrain the $cc{Z}^{\prime }$ coupling, and that the $Z^{\prime }$ can be discovered in either or both of the $cg\to t{Z}^{\prime }$ and $c\bar{c}\to Z^{\prime }$ processes. We further discuss the sensitivity to the left-handed $tc{Z}^{\prime }$ coupling and find that the coupling values favored by the $B\to K^{(\ast )}$ anomalies lie slightly below the LHC discovery reach even with 3000 fb${}^{-1}$.

    hep-phhep-exPRD(2017)·24 citations
12. 12*

    Vector boson-tagged jet production in heavy ion collisions at the LHC

    Zhong-Bo Kang🇺🇸 · Ivan Vitev🇺🇸 · Hongxi Xing🇺🇸

    Vector boson-tagged jet production in collisions of heavy nuclei opens new opportunities to study parton shower formation and propagation in strongly interacting matter. It has been argued to provide a golden channel that can constrain the energy loss of jets in the quark-gluon plasma created in heavy ion reactions. We present theoretical results for isolated photon-tagged and $Z^0$ boson-tagged jet production in Pb+Pb collisions with $\sqrt{s_{NN}}=5.02$ TeV at the LHC. Specifically, we evaluate the transverse momentum imbalance ${\mathrm{x}}_{\mathrm{JV}}$ distribution and nuclear modification factor ${\mathrm{I}}_{\mathrm{AA}}$ of tagged jets and compare our theoretical calculations to recent experimental measurements by ATLAS and CMS collaborations. Our analysis, which includes both collisional and radiative energy losses, sheds light on their relative importance versus the strength of jet-medium interactions and helps quantify the amount of out-of-cone radiation of predominantly prompt quark-initiated jets.

    hep-phnucl-thPRC(2017)·45 citations
13. 13*

    Hadronic structure functions in the $e^{+}{e}^{-}\to \bar{\Lambda }\Lambda$ reaction

    Göran Fäldt🇸🇪 · Andrzej Kupsc🇸🇪

    Cross-section distributions are calculated for the reaction $e^{+}{e}^{-}\to J/\psi \to \bar{\Lambda }(\to \bar{p}{\pi }^{+})\Lambda (\to p{\pi }^{-})$, and related annihilation reactions mediated by vector mesons. The hyperon-decay distributions depend on a number of structure functions that are bilinear in the, possibly complex, psionic form factors $G_M^{\psi }$ and $G_E^{\psi }$ of the Lambda hyperon. The relative size and relative phase of these form factors can be uniquely determined from the unpolarized joint-decay distributions of the Lambda and anti-Lambda hyperons. Also the decay-asymmetry parameters of Lambda and anti-Lambda hyperons can be determined.

    hep-phPLB(2017)·140 citations
14. 14*

    Two-loop master integrals for the leading QCD corrections to the Higgs coupling to a $W$ pair and to the triple gauge couplings $ZWW$ and ${\gamma }^{\ast }WW$

    Stefano Di Vita🇩🇪 · Pierpaolo Mastrolia🇮🇹 · Amedeo Primo🇮🇹 · Ulrich Schubert🇺🇸

    We compute the two-loop master integrals required for the leading QCD corrections to the interaction vertex of a massive neutral boson $X^0$, e.g. $H,Z$ or ${\gamma }^{\ast }$, with a pair of $W$ bosons, mediated by a $SU(2{)}_L$ quark doublet composed of one massive and one massless flavor. All the external legs are allowed to have arbitrary invariant masses. The Magnus exponential is employed to identify a set of master integrals that, around $d=4$ space-time dimensions, obey a canonical system of differential equations. The canonical master integrals are given as a Taylor series in $ϵ=(4-d)/2$, up to order four, with coefficients written as combination of Goncharov polylogarithms, respectively up to weight four. In the context of the Standard Model, our results are relevant for the mixed EW-QCD corrections to the Higgs decay to a $W$ pair, as well as to the production channels obtained by crossing, and to the triple gauge boson vertices $ZWW$ and ${\gamma }^{\ast }WW$.

    hep-phhep-thJHEP(2017)·27 citations
15. 15*

    Dispersion relation for hadronic light-by-light scattering: two-pion contributions

    Gilberto Colangelo🇨🇭 · Martin Hoferichter🇺🇸 · Massimiliano Procura🇨🇭 · Peter Stoffer🇺🇸

    In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon $(g-2{)}_{\mu }$, including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of ${\gamma }^{\ast }{\gamma }^{\ast }\to \pi \pi$. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, $a_{\mu }^{\pi \text{-box}}=-15.9(2)\times 10^{-11}$. As an application of the partial-wave formalism, we present a first calculation of $\pi \pi$-rescattering effects in HLbL scattering, with ${\gamma }^{\ast }{\gamma }^{\ast }\to \pi \pi$ helicity partial waves constructed dispersively using $\pi \pi$ phase shifts derived from the inverse-amplitude method. In this way, the isospin-$0$ part of our calculation can be interpreted as the contribution of the $f_0(500)$ to HLbL scattering in $(g-2{)}_{\mu }$. We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its $S$-wave rescattering corrections reads $a_{\mu }^{\pi \text{-box}}+a_{\mu ,J=0}^{\pi \pi ,\pi \text{-pole LHC}}=-24(1)\times 10^{-11}$.

    hep-phhep-exhep-latnucl-thJHEP(2017)·557 citations
16. 16*

    ${\rm Y}$ and $\psi$ leptonic decays as probes of solutions to the $R_D^{(\ast )}$ puzzle

    Daniel Aloni🇮🇱 · Aielet Efrati🇮🇱 · Yuval Grossman🇺🇸 · Yosef Nir🇮🇱

    Experimental measurements of the ratios $R(D^{(\ast )})\equiv \frac{\Gamma (B\to D^{(\ast )}\tau \nu )}{\Gamma (B\to D^{(\ast )}\ell \nu )}$ ($\ell =e,\mu$) show a $3.9\sigma$ deviation from the Standard Model prediction. In the absence of light right-handed neutrinos, a new physics contribution to $b\to c\tau \nu$ decays necessarily modifies also $b\bar{b}\to {\tau }^{+}{\tau }^{-}$ and/or $c\bar{c}\to {\tau }^{+}{\tau }^{-}$ transitions. These contributions lead to violation of lepton flavor universality in, respectively, ${\rm Y}$ and $\psi$ leptonic decays. We analyze the constraints resulting from measurements of the leptonic vector-meson decays on solutions to the $R(D^{(\ast )})$ puzzle. Available data from BaBar and Belle can already disfavor some of the new physics explanations of this anomaly. Further discrimination can be made by measuring ${\rm Y}(1S,2S,3S)\to \tau \tau$ in the upcoming Belle II experiment.

    hep-phJHEP(2017)·45 citations
17. 17*

    12 GeV CEBAF - The Physics and Experiments

    Volker D. Burkert🇺🇸

    In this talk the role of spin and polarization is discussed in experimental search for new excited baryon states and in the study of the internal quark-gluon structure of the proton and neutron. Also the perspective of spin physics at the 12 GeV CEBAF electron accelerator is discussed and what we hope to learn about fundamental properties of hadrons such as their multi-dimensional structure through the momentum and spatial imaging, and about the forces on the quarks in the proton and how quark confinement may be realized through the spatial distribution of such forces.

    ↳ nucl-exhep-phnucl-th1 citation
18. 18*

    More efficient formulas for efficiency correction of cumulants and effect of using averaged efficiency

    Toshihiro Nonaka🇯🇵 · Masakiyo Kitazawa🇯🇵 · ShinIchi Esumi🇯🇵

    We derive formulas for the efficiency correction of cumulants with many efficiency bins. The derivation of the formulas is simpler than the previously suggested method, but the numerical cost is drastically reduced from the naive method. From analytical and numerical analyses in simple toy models, we show that the use of the averaged efficiency in the efficiency correction can lead to wrong corrected values, which have larger deviation for higher order cumulants. These analyses show the importance of carrying out the efficiency correction without taking the average.

    ↳ physics.data-anhep-phnucl-exnucl-thPRC(2017)·83 citations
19. 19*

    Fifty years of cosmological particle creation

    Leonard Parker🇺🇸 · Jose Navarro-Salas🇪🇸

    In the early sixties Leonard Parker discovered that the expansion of the universe can create particles out of the vacuum, opening a new and fruitfull field in physics. We give a historical review in the form of an interview that took place during the Conference ERE2014 (Valencia 1-5, September, 2014).

    ↳ physics.hist-phastro-ph.COgr-qchep-ph+119 citations
20. 20*

    Measurement of Anisotropy and Search for UHECR Sources

    O. Deligny (1)🇫🇷 · K. Kawata (2)🇯🇵 · P. Tinyakov (3) ((1) Univ. Paris-Sud, Orsay, (2) ICRR, University of Tokyo, (3) Universite Libre de Bruxelles)🇧🇪

    Ultra-high energy cosmic rays (UHECRs) are particles, likely protons and/or nuclei, with energies up to $10^{20}$ eV that are observed through the giant air showers they produce in the atmosphere. These particles carry the information on the most extreme phenomena in the Universe. At these energies, even charged particles could be magnetically rigid enough to keep track of, or even point directly to, the original positions of their sources on the sky. The discovery of anisotropy of UHECRs would thus signify opening of an entirely new window onto the Universe. With the construction and operation of the new generation of cosmic ray experiments -- the Pierre Auger Observatory in the Southern hemisphere and the Telescope Array in the Northern one -- the study of these particles, the most energetic ever detected, has experienced a jump in statistics as well as in the data quality, allowing for a much better sensitivity in searching for their sources. In this review, we summarize the searches for anisotropies and the efforts to identify the sources of UHECRs which have been carried out using these new data.

    ↳ astro-ph.HEhep-phPTEP(2017)·12 citations
21. 21*

    An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: hard probes

    Panagiota Foka🇩🇪 · Malgorzata Anna Janik🇵🇱

    The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is currently experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. The more than a factor 10 increase of collision energy at LHC, relative to the previously achieved maximal energy at other collider facilities, results in an increase of production rates of hard probes. This review presents selected experimental results focusing on observables probing hard processes in heavy-ion collisions delivered during the first three years of the LHC operation. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.

    ↳ hep-exhep-phnucl-exnucl-thRev.Phys.(2016)·60 citations
22. 22*

    An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: bulk properties and dynamical evolution

    Panagiota Foka🇩🇪 · Malgorzata Anna Janik🇵🇱

    The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. Following the Run 1 period, LHC also successfully delivered PbPb collisions at the collision energy $\sqrt{s_{NN}}$ = 5.02 TeV at the end of 2015. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. This review presents selected experimental results from heavy-ion collisions delivered during the first three years of the LHC operation focusing on the bulk matter properties and the dynamical evolution of the created system. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.

    ↳ hep-exhep-phnucl-exnucl-thRev.Phys.(2016)·89 citations
23. 23*

    Azimuthal asymmetries in SIDIS di-hadron muoproduction off longitudinally polarized protons at COMPASS

    Stefan Sirtl🇩🇪

    In this review a first comprehensive study of azimuthal asymmetries in semi-inclusive deep inelastic muoproduction of hadron pairs off longitudinally polarized protons at COMPASS is presented. The study is based on data taken in 2007 and 2011, obtained by impinging a high-energetic ${\mu }^{+}$ beam of $160$ GeV/$c$, respectively $200$ GeV/$c$, momentum on a solid ammonia target. The discussion is focused on both leading and subleading longitudinal target-spin-dependent asymmetries arising in the di-hadron SIDIS cross section, addressing the role of spin-orbit couplings and quark-gluon correlations in the framework of collinear or transverse momentum dependent factorization.

    ↳ hep-exhep-ph17 citations
24. 24*

    Taming instability of magnetic field in chiral medium

    Kirill Tuchin🇺🇸

    Magnetic field is unstable in a medium with time-independent chiral conductivity. Owing to the chiral anomaly, the electromagnetic field and the medium exchange helicity which results in time-evolution of the chiral conductivity. Using the fastest growing momentum and helicity state of the vector potential as an ansatz, the time-evolution of the chiral conductivity and magnetic field is solved analytically. The solution for the hot and cold equations of state shows that the magnetic field does not develop an instability due to he helicity conservation. Moreover, it develops a peak only if a significant part of the \emph{initial} helicity is stored in the medium. The initial helicity determines the height and position of the peak.

    ↳ nucl-thhep-phhep-thNPA(2018)·17 citations
25. 25*

    Quantum Radiation Properties of General Nonstationary Black Hole

    T. Ibungochouba Singh🇮🇳

    Using the generalized tortoise coordinate transformations the quantum radiation properties of Klein-Gordon scalar particles, Maxwell's electromagnetic field equations and Dirac equations are investigated in general non-stationary black hole. The locations of the event horizon and the Hawking temperature depend on both time and angles. A new extra coupling effect is observed in the thermal radiation spectrum of Maxwell's equations and Dirac equations which is absent in the thermal radiation spectrum of scalar particles. We also observe that the chemical potential derived from scalar particles is equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation in general non-stationary black hole. Applying generalized tortoise coordinate transformation a constant term $\xi$ is produced in the expression of thermal radiation in general non-stationary black hole. It indicates that generalized tortoise coordinate transformation is more accurate and reliable in the study of thermal radiation of black hole.

    ↳ gr-qchep-phAdv.High Energy Phys.(2017)·8 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.