Thu·Dec 20, 2018Thursday·December 20, 2018

1. 01*

   Exploring the Structure of the Bound Proton with Deeply Virtual Compton Scattering

   M. Hattawy · N.A. Baltzell · R. Dupré · S. Bültmann · R. De Vita · A. El Alaoui · L. El Fassi · H. Egiyan · F.X. Girod · M. Guidal · K. Hafidi · D. Jenkins and 116 other authors

   In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this work, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering (DVCS) off a proton bound in ${}^4$He. The data used here were accumulated using a $6$ GeV longitudinally polarized electron beam incident on a pressurized ${}^4$He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle ($\varphi$) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The $Q^2$, $x_B$, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20\% to 40\%, indicating possible medium modification of its partonic structure.

   nucl-exhep-exPRL(2019)·38 citations
2. 02*

   Inclusive jet measurements in pp and Pb-Pb collisions with ALICE

   James Mulligan (for the ALICE Collaboration)🇺🇸

   Measurements of jet yields in heavy-ion collisions can be used to constrain jet energy loss models, and in turn provide information about the physical properties of deconfined QCD matter. ALICE reconstructs charged particle jets ($\text{charged jets}$) with high-precision tracking of charged particles down to $p_{\mathrm{T}}^{\mathrm{track}}=150$ MeV/$c$, and jets ($\text{full jets}$) with the addition of particle information from the electromagnetic calorimeter down to $E_{\mathrm{cluster}}=300$ MeV. By including low momentum jet constituents, ALICE is uniquely positioned at the LHC to measure jets down to low jet momentum, to determine the modification to the soft components of jets, and to measure medium recoil particles. New inclusive full jet measurements in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ALICE will be shown, over $R=0.2-0.4$ and extending to low jet $p_{\mathrm{T}}$. These will include the jet $R_{\mathrm{AA}}$ for different jet $R$, and will constitute the first such full jet measurements at low transverse jet momentum at this collision energy. The results are compared to several theoretical predictions.

   nucl-exPoS(2019)·4 citations
3. 03*

   Study of hard and electromagnetic processes at CERN-SPS energies: an investigation of the high-${\mu }_{\mathbf{B}}$ region of the QCD phase diagram with NA60+

   M. Agnello · F. Antinori🇮🇹 · H. Appelshäuser🇩🇪 · R. Arnaldi🇮🇹 · R. Bailhache🇩🇪 · L. Barioglio🇮🇹 · S. Beole🇮🇹 · A. Beraudo🇮🇹 · A. Bianchi · L. Bianchi · E. Bruna🇮🇹 · S. Bufalino🇮🇹 and 60 other authors

   The exploration of the phase diagram of Quantum ChromoDynamics (QCD) is carried out by studying ultrarelativistic heavy-ion collisions. The energy range covered by the CERN SPS ($\sqrt{s_{\mathrm{NN}}}\sim$ 6-17 GeV) is ideal for the investigation of the region of the phase diagram corresponding to finite baryochemical potential (${\mu }_{\mathrm{B}}$), and has been little explored up to now. We propose in this document a new experiment, NA60+, that would address several observables which are fundamental for the understanding of the phase transition from hadronic matter towards a Quark-Gluon Plasma (QGP) at SPS energies. In particular, we propose to study, as a function of the collision energy, the production of thermal dimuons from the created system, from which one would obtain a caloric curve of the QCD phase diagram that is sensitive to the order of the phase transition. In addition, the measurement of a $\rho$-a${}_1$ mixing contribution would provide conclusive insights into the restoration of the chiral symmetry of QCD. In parallel, studies of heavy quark and quarkonium production would also be carried out, addressing the measurement of transport properties of the QGP and the investigation of the onset of the deconfinement transition. The document also defines an experimental set-up which couples a vertex telescope based on monolithic active pixel sensors (MAPS) to a muon spectrometer with tracking (GEM) and triggering (RPC) detectors within a large acceptance toroidal magnet. Results of physics performance studies for most observables accessible to NA60+ are discussed, showing that the results of the experiment would lead to a significant advance of our understanding of strong interaction physics. The document has been submitted as an input to the European Particle Physics Strategy Update 2018-2020 (http://europeanstrategyupdate.web.cern.ch/).

   nucl-exJPS Conf.Proc.(2021)·20 citations
4. 04*

   Semi-inclusive jets recoiling from ${\gamma }_{dir}$ and ${\pi }^0$ triggers in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV in STAR

   Nihar Ranjan Sahoo (For the STAR Collaboration)🇺🇸

   We report the first measurement of fully corrected semi-inclusive charged recoil jets for both direct-photon (${\gamma }_{dir}$) and ${\pi }^0$ triggers, within two trigger transverse energy ranges between 9 GeV and 15 GeV, in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV using data with an integrated luminosity of 13 $\mathrm{n}{\mathrm{b}}^{-1}$ collected by the STAR experiment. A comparison between ${\pi }^0$-triggered recoil jets in p+p collisions and PYTHIA is discussed. A comparison is also presented between the suppression of ${\gamma }_{dir}$- and ${\pi }^0$-triggered recoil jets in central Au+Au collisions with respect to their corresponding PYTHIA references. A strong and similar level of suppression is observed in recoil-jet yields as a function of jet transverse momentum for ${\gamma }_{dir}$+jet and ${\pi }^0$+jet.

   nucl-exhep-exhep-phnucl-thPoS(2018)·1 citation
5. 05*

   Nucleon-nucleon correlations and the single-particle strength in atomic nuclei

   S. Paschalis🇩🇪 · M. Petri🇩🇪 · A.O. Macchiavelli🇺🇸 · O. Hen🇺🇸 · E. Piasetzky🇮🇱

   We propose a phenomenological approach to examine the role of short- and long-range nucleon-nucleon correlations in the quenching of single-particle strength in atomic nuclei and their evolution in asymmetric nuclei and neutron matter. These correlations are thought to be the reason for the quenching of spectroscopic factors observed in $(\mathrm{e},{\mathrm{e}}^{\prime }\mathrm{p})$, $(\mathrm{p},2p)$ and transfer reactions. We show that the recently observed increase of the high-momentum component of the protons in neutron-rich nuclei is consistent with the reduced proton spectroscopic factors. Our approach connects recent results on short-range correlations from high-energy electron scattering experiments with the quenching of spectroscopic factors and addresses for the first time quantitatively this intriguing question in nuclear physics, in particular regarding its isospin dependence. We also speculate about the nature of a {\sl quasi-proton} (nuclear polaron) in neutron matter and its kinetic energy, an important quantity for the properties of neutron stars.

   nucl-exnucl-thPLB(2020)·36 citations
6. 06*

   Direct photon production and flow at low transverse momenta in pp, p-Pb and Pb-Pb collisions

   Nicolas Schmidt (for the ALICE Collaboration)🇺🇸

   Low transverse momentum direct photon measurements have been carried out by the ALICE experiment at the CERN LHC in small collision systems (pp, $\sqrt{s}=2.76$ and 8 TeV and p--Pb, $\sqrt{s_{\text{NN}}}=5.02$ TeV) as well as in heavy-ion collisions (Pb--Pb, $\sqrt{s_{\text{NN}}}=2.76$ TeV). For the first time, also the multiplicity dependence of direct photon production was investigated in p--Pb collisions. Whereas in the small systems no significant thermal photon signal was observed, a $\sim 15\%$ excess has been measured in central Pb--Pb collisions in the region of $p_{\mathrm{T}}<3$ GeV/$c$. A signal of prompt photon production at high transverse momentum consistent with binary scaling has been observed in all collision systems following NLO pQCD predictions. Direct photon flow has been measured in central and semi-central Pb--Pb collisions and found to be of similar size as the charged hadron and decay photon flow.

   nucl-exhep-exhep-phnucl-thPoS(2018)·7 citations
7. 07*

   Nuclear Dependence of Transverse Single-Spin Asymmetries in Polarized $p$+$A$ Collisions at RHIC

   Stephen Pate (for the PHENIX Collaboration)🇺🇸

   Large transverse single-spin asymmetries (TSSA) in hadron production at forward rapidity have been observed in polarized $p$+$p$ interactions for many decades, over a large range of center-of-mass energies, and have led to the investigation of spin-momentum correlations such as the Sivers and Collins effects. In the last few years, it has been discovered at RHIC that these single-spin asymmetries may be enhanced or suppressed in $p$+$A$ collisions, and the nuclear-size and centrality dependence have been studied. A variety of phenomena have been observed and likely they do not have all a single explanation; we see an apparent quenching of the TSSA in forward charged hadron production with increasing nuclear size, while we see an enhancement in the asymmetry in $J/\psi$ production, and in very forward neutron production even a sign change in the asymmetry is seen. Other systems, such as ${\pi }^0$ production at central rapidity, do not display a nuclear-size dependence. These observations provide a bridge between the study of the initial state in heavy-ion collisions and that of the nucleon spin puzzle, and open up a new method for the investigation of cold nuclear matter.

   nucl-ex0 citations
8. 08*

   Comparison of Plastic Antineutrino Detector Designs in the Context of Near Field Reactor Monitoring

   Mustafa Kandemir🇹🇷 · Altan Cakir🇹🇷

   We compare existing segmented plastic antineutrino detectors with our new geometrically improved design for antineutrino detection and light collection efficiency. The purpose of this study is to determine the most suitable design style for remote reactor monitoring in the context of nuclear safeguards. Using Monte Carlo based GEANT4 simulation package, we perform detector simulation based on two prominent experiments: Plastic antineutrino detector array (Panda) and Core monitoring by reactor antineutrino detector (Cormorad). In addition to these two well-known designs, another concept, the Panda2, can be obtained by making a small variation of Panda detector, is also considered in the simulation. The results show that the light collection efficiency of the Cormorad is substantially less with respect to the other two detectors while the highest antineutrino detection efficiency is achieved with the Cormorad and Panda2. Furthermore, as an alternative to these design choices, which are composed of an array of identical rectangular-shaped modules, we propose to combine regular hexagonal-shaped modules which minimizes the surface area of the whole detector and consequently reduces the number of optical readout channels considerably. With this approach, it is possible to obtain a detector configuration with a slightly higher detection efficiency with respect to the Panda design and a better energy resolution detector compared to the Cormorad design.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2019)·5 citations
9. 09*

   New physics searches with heavy-ion collisions at the LHC

   Roderik Bruce🇨🇭 · David d'Enterria🇨🇭 · Albert de Roeck🇨🇭 · Marco Drewes🇧🇪 · Glennys R. Farrar🇺🇸 · Andrea Giammanco🇧🇪 · Oliver Gould🇫🇮 · Jan Hajer🇧🇪 · Lucian Harland-Lang🇬🇧 · Jan Heisig🇧🇪 · John M. Jowett🇨🇭 · Sonia Kabana🇫🇷 and 9 other authors

   This document summarises proposed searches for new physics accessible in the heavy-ion mode at the CERN Large Hadron Collider (LHC), both through hadronic and ultraperipheral $\gamma \gamma$ interactions, and that have a competitive or, even, unique discovery potential compared to standard proton-proton collision studies. Illustrative examples include searches for new particles -- such as axion-like pseudoscalars, radions, magnetic monopoles, new long-lived particles, dark photons, and sexaquarks as dark matter candidates -- as well as new interactions, such as non-linear or non-commutative QED extensions. We argue that such interesting possibilities constitute a well-justified scientific motivation, complementing standard quark-gluon-plasma physics studies, to continue running with ions at the LHC after the Run-4, i.e. beyond 2030, including light and intermediate-mass ion species, accumulating nucleon-nucleon integrated luminosities in the accessible fb${}^{-1}$ range per month.

   ↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·95 citations
10. 10*

    Lepton-jet Correlations in Deep Inelastic Scattering at the Electron-Ion Collider

    Xiaohui Liu🇨🇳 · Felix Ringer🇺🇸 · Werner Vogelsang🇩🇪 · Feng Yuan🇺🇸

    We propose the lepton-jet correlation in deep inelastic scattering as a unique tool for nucleon/nucleus tomography at the electron-ion collider. The azimuthal angular correlation between the final state lepton and jet depends on the transverse momentum dependent quark distributions. We take the example of single transverse spin asymmetries to show the sensitivity to the quark Sivers function. When the correlation is studied in lepton-nucleus collisions, transverse momentum broadening effects can be used to explore cold nuclear matter effects. These features make lepton-jet correlations an important new hard probe at the EIC.

    ↳ hep-phnucl-exnucl-thPRL(2019)·113 citations
11. 11*

    Exploring New Small System Geometries in Heavy Ion Collisions

    S.H. Lim🇺🇸 · J. Carlson🇺🇸 · C. Loizides🇺🇸 · D. Lonardoni🇺🇸 · J.E. Lynn🇩🇪 · J.L. Nagle🇺🇸 · J.D. Orjuela Koop🇺🇸 · J. Ouellette🇺🇸

    Relativistic heavy ion collisions produce nuclei-sized droplets of quark-gluon plasma whose expansion is well described by viscous hydrodynamic calculations. Over the past half decade, this formalism was also found to apply to smaller droplets closer to the size of individual nucleons, as produced in $p$$+$$p$ and $p$$+$$A$ collisions. The hydrodynamic paradigm was further tested with a variety of collision species, including $p$$+$Au, $d$$+$Au, and ${}^3$He$+$Au producing droplets with different geometries. Nevertheless, questions remain regarding the importance of pre-hydrodynamic evolution and the exact medium properties during the hydrodynamic evolution phase, as well as the applicability of alternative theories that argue the agreement with hydrodynamics is accidental. In this work we explore options for new collision geometries including $p$$+$O and O$+$O proposed for running at the Large Hadron Collider, as well as, ${}^4$He$+$Au, C$+$Au, O$+$Au, and ${}^{7,9}$Be$+$Au at the Relativistic Heavy Ion Collider.

    ↳ nucl-thnucl-exPRC(2019)·67 citations
12. 12*

    The "DIS and Related Subjects" Strategy Document: Fundamental Science from Lepton-Hadron Scattering

    Allen Caldwell🇩🇪 · Rolf Ent🇺🇸 · Aharon Levy🇮🇱 · Paul Newman🇬🇧 · Fred Olness🇺🇸

    The diverse community of scientists involved in Deep Inelastic Scattering includes about 2000 experimental and theoretical physicists worldwide and envisages projects such as the EIC, LHeC, FCC-eh and VHEeP as future lepton-hadron scattering facilities. The proposed facilities will address fundamental questions in strong interaction / QCD physics, including a first-ever tomographic mapping of the hadrons' internal structure, a solution to the proton mass and spin problems, understanding of the high-energy structure of hadronic matter and insight into connections between gravity and the strong interactions. They also extend and enhance the CERN programme of searches for new physics at the energy frontier, through a standalone precision Higgs and top programme, considerable sensitivity to the direct production of new particles and the most precise determinations of proton and nuclear structure in the kinematic range that is relevant to the LHC. In particular, we highlight the complementary aspects of the different lepton-hadron projects, and underscore how all are required to provide a complete characterization of the physics across the full kinematic reach. This review of the proposed facilities and their vast potential for particle physics was inspired by the discussions in the 2018 "DIS and Related Subjects" Workshop.

    ↳ hep-phhep-exnucl-ex7 citations
13. 13*

    Recent results from the MAJORANA DEMONSTRATOR

    J. Myslik🇺🇸 · S. I. Alvis🇺🇸 · I. J. Arnquist🇺🇸 · F. T. Avignone III🇺🇸 · A. S. Barabash🇷🇺 · C. J. Barton🇺🇸 · F. E. Bertrand🇺🇸 · T. Bode🇩🇪 · B. Bos🇺🇸 · V. Brudanin🇷🇺 · M. Busch🇺🇸 · M. Buuck🇺🇸 and 56 other authors

    The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decay in ${}^{76}$Ge and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modules of natural and ${}^{76}$Ge-enriched germanium detectors totalling 44.1 kg, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Commissioning of the experiment began in June 2015, followed by data production with the full detector array in August 2016. The ultra-low background and record energy resolution achieved by the MAJORANA DEMONSTRATOR enable a sensitive neutrinoless double-beta decay search, as well as additional searches for physics beyond the Standard Model. I will discuss the design elements that enable these searches, along with the latest results, focusing on the neutrinoless double-beta decay search. I will also discuss the current status and the future plans of the MAJORANA DEMONSTRATOR, as well as the plans for a future tonne-scale ${}^{76}$Ge experiment.

    ↳ physics.ins-detnucl-exPoS(2019)·0 citations
14. 14*

    PHOTON-2017 conference proceedings

    David d'Enterria · Albert de Roeck · Michelangelo Mangano (eds.) · Jaroslav Adam · Massimiliano Alvioli · Christopher D. Anson · Hamed Bakhshiansohi · Cristian Baldenegro · Valerio Bertone · Stanley J. Brodsky · Peter J. Bussey · Chav Chhiv Chau and 69 other authors

    This document collects the proceedings of the PHOTON 2017 conference ("International Conference on the Structure and the Interactions of the Photon", including the 22th "International Workshop on Photon-Photon Collisions", and the "International Workshop on High Energy Photon Colliders") held at CERN (Geneva) in May 2017. The latest experimental and theoretical developments on the topics of the PHOTON conference series are covered: (i) $\gamma \gamma$ processes in e${}^{+}$e${}^{-}$, proton-proton (pp) and nucleus-nucleus (AA) collisions at current and future colliders, (ii) $\gamma$-hadron interactions in e${}^{\pm }$p, pp, and AA collisions, (iii) final-state photon production (including Standard Model studies and searches beyond it) in pp and AA collisions, and (iv) high-energy $\gamma$-ray astrophysics. These proceedings are dedicated to the memory of Maria Krawczyk.

    ↳ hep-phhep-exnucl-exnucl-thCERN Proc.(2018)·6 citations
15. 15*

    Event-shape engineering and heavy-flavour observables in relativistic heavy-ion collisions

    A. Beraudo🇮🇹 · A. De Pace🇮🇹 · M. Monteno🇮🇹 · M. Nardi🇮🇹 · F. Prino🇮🇹

    Traditionally, events collected at relativistic heavy-ion colliders are classified according to some centrality estimator (e.g. the number of produced charged particles) related to the initial energy density and volume of the system. In a naive picture the latter are directly related to the impact parameter of the two nuclei, which sets also the initial eccentricity of the system: zero in the case of the most central events and getting larger for more peripheral collisions. A more realistic modelling requires to take into account event-by-event fluctuations, in particular in the nucleon positions within the colliding nuclei: collisions belonging to the same centrality class can give rise to systems with different initial eccentricity and hence different flow harmonics for the final hadron distributions. This issue can be addressed by an event-shape-engineering analysis, consisting in selecting events with the same centrality but different magnitude of the average bulk anisotropic flow and therefore of the initial-state eccentricity. In this paper we present the implementation of this analysis in the POWLANG transport model, providing predictions for the transverse-momentum and angular distributions of charm and beauty hadrons for event-shape selected collisions. In this way it is possible to get information on how the heavy quarks propagating (and hadronizing) in a hot environment respond both to its energy density and to its geometric asymmetry, breaking the perfect correlation between eccentricity and impact parameter which characterizes a modelling of the medium based on smooth average initial conditions

    ↳ physics.data-anhep-phnucl-exnucl-thEPJC(2019)·20 citations
16. 16*

    Response of a Li-glass/multi-anode photomultiplier detector to $\alpha$-particles from ${}^{241}$Am

    E. Rofors🇸🇪 · H. Perrey🇸🇪 · R. Al Jebali🇸🇪 · J.R.M. Annand🇬🇧 · L. Boyd🇬🇧 · U. Clemens🇩🇪 · S. Desert🇫🇷 · R. Engels🇩🇪 · K.G. Fissum🇸🇪 · H. Frielinghaus🇩🇪 · C. Gheorghe🇳🇴 · R. Hall-Wilton🇸🇪 and 9 other authors

    The response of a position-sensitive Li-glass scintillator detector to $\alpha$-particles from a collimated ${}^{241}$Am source scanned across the face of the detector has been measured. Scintillation light was read out by an 8 X 8 pixel multi-anode photomultiplier and the signal amplitude for each pixel has been recorded for every position on a scan. The pixel signal is strongly dependent on position and in general several pixels will register a signal (a hit) above a given threshold. The effect of this threshold on hit multiplicity is studied, with a view to optimize the single-hit efficiency of the detector.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·6 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.