Tue·Jun 25, 2019Tuesday·June 25, 2019

1. 01*

   Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV

   STAR Collaboration

   High transverse momentum ($p_T$) particle production is suppressed due to parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest $p_T$ has been elusive to measure because of large anisotropic backgrounds. We report a data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV with the STAR experiment. The correlation shapes, for trigger particle $p_T>3$ GeV/$c$ and various associated particle $p_T$ ranges within $0.5<p_T<10$ GeV/$c$, are consistent with Gaussians and their widths are found to increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.

   nucl-exCPC(2020)·2 citations
2. 02*

   Physics with Positron Beams at Jefferson Lab 12 GeV

   A. Afanasev · I. Albayrak · S. Ali · M. Amaryan · A. D'Angelo · J. Annand · J. Arrington · A. Asaturyan · H. Avakian · T. Averett · L. Barion · M. Battaglieri and 115 other authors

   Positron beams, both polarized and unpolarized, are identified as essential ingredients for the experimental program at the next generation of lepton accelerators. In the context of the Hadronic Physics program at the Jefferson Laboratory (JLab), positron beams are complementary, even essential, tools for a precise understanding of the electromagnetic structure of the nucleon, in both the elastic and the deep-inelastic regimes. For instance, elastic scattering of (un)polarized electrons and positrons off the nucleon allows for a model independent determination of the electromagnetic form factors of the nucleon. Also, the deeply virtual Compton scattering of (un)polarized electrons and positrons allows us to separate unambiguously the different contributions to the cross section of the lepto-production of photons, enabling an accurate determination of the nucleon Generalized Parton Distributions (GPDs), and providing an access to its Gravitational Form Factors. Furthermore, positron beams offer the possibility of alternative tests of the Standard Model through the search of a dark photon or the precise measurement of electroweak couplings. This letter proposes to develop an experimental positron program at JLab to perform unique high impact measurements with respect to the two-photon exchange problem, the determination of the proton and the neutron GPDs, and the search for the $A^{\prime }$ dark photon.

   nucl-exhep-ex14 citations
3. 03*

   Measurement of $\gamma$ rays from the giant resonances excited by ${}^{12}$C$(p,p^{\prime })$ reaction at 392 MeV and 0${}^{\circ }$

   M. S. Reen🇯🇵 · I. Ou🇯🇵 · T. Sudo🇯🇵 · D. Fukuda🇯🇵 · T. Mori · A.Ali🇯🇵 · Y. Koshio🇯🇵 · M. Sakuda🇯🇵 · A. Tamii🇯🇵 · N. Aoi🇯🇵 · M. Yosoi🇯🇵 · E. Ideguchi🇯🇵 and 12 other authors

   We measured both the differential cross section (${\sigma }_{p,p^{\prime }}$ $=d^2\sigma /d\Omega d{E}_x$) and the $\gamma$-ray emission probability ($R_{\gamma }(E_x)$ $={\sigma }_{p,p^{\prime }\gamma }$/${\sigma }_{p,p^{\prime }}$) from the giant resonances excited by ${}^{12}\mathrm{C}$(\textit{p,p}${}^{\prime }$) reaction at 392 MeV and 0${}^{\circ }$, using a magnetic spectrometer and an array of NaI(Tl) counters. The absolute value of $R_{\gamma }(E_x)$ was calibrated by using the well-known $\gamma$-ray emission probability from ${}^{12}{\mathrm{C}}^{\ast }(15.11$ MeV, $1^{+}$, $T=1$) and ${}^{16}{\mathrm{O}}^{\ast }(6.9$ MeV, $2^{+}$, $T=0$) states within 5\% uncertainty. We found that $R_{\gamma }(E_x)$ starts from zero at $E_x=16$ MeV, increases to a maximum of 53.3$\pm$0.4$\pm$3.9\% at $E_x=27$ MeV and then decreases. We also compared the measured values of $R_{\gamma }(E_x)$ with statistical model calculation based on the Hauser-Feshbach formalism in the energy region $E_x=$ 16-32 MeV and discussed the features of $\gamma$-ray emission probability quantitatively.

   nucl-exPRC(2019)·7 citations
4. 04*

   Perspectives of photon physics at future colliders

   M. Klasen🇩🇪

   We review current results on physics with photons at the LHC and discuss realistic perspectives of photon physics at future colliders. In particular, we focus on Standard Model (SM) measurements with photons at the upcoming high-luminosity and a possible high-energy LHC as well as jet measurements at an Electron-Ion Collider (EIC) to be constructed either at BNL or at JLAB and their potential to constrain nuclear parton densities. We also discuss future searches for physics beyond the SM with photons in the high-luminosity phase of the LHC.

   ↳ hep-phhep-exnucl-exnucl-thFrascati Phys.Ser.(2019)·3 citations
5. 05*

   Nuclear modification of jet shape for inclusive jets and $\gamma$-jets at the LHC energies

   Ning-Bo Chang🇨🇳 · Yasuki Tachibana🇺🇸 · Guang-You Qin🇨🇳

   With our coupled jet-fluid model, we study the nuclear modifications of full jets and jet structures for single inclusive jets and $\gamma$-jets in Pb+Pb collisions at $5.02$~ATeV and $2.76$~ATeV. The in-medium evolution of full jet shower is described by a set of coupled transport equations including the effects of collisional energy loss, transverse momentum broadening and medium-induced splitting process. The dynamical evolution of bulk medium is simulated by solving relativistic hydrodynamic equation with source term which accounts for the energy and momentum deposited by hard jet shower to soft medium. Our study demonstrates that the hydrodynamic medium response to jet propagation significantly enhances the broadening of jet shape at large angles and is essential for the cone-size dependence of jet energy loss and nuclear modification factor of inclusive jet production. It is also found that the nuclear modification pattern of jet shape is sensitive to jet energy but has weak dependence on the flavor of the parton that initiates the jet. Our result can naturally explain the different nuclear modification patterns of jet shape functions for single inclusive jet and $\gamma$-jet events as observed by the CMS Collaboration, and can be tested in the future by measuring the jet shape function over a wider range of jet energies in heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exPLB(2020)·60 citations
6. 06*

   Radiative corrections to Gamow-Teller decays

   Leendert Hayen🇧🇪 · Nathal Severijns🇧🇪

   Radiative corrections in the electroweak sector constitute an essential component in the ability to disentangle Beyond Standard Model physics from experimental data. This is particularly relevant for strongly bound systems undergoing weak decays such as nuclear $\beta$ decay, where its contribution to top-row CKM unitarity tests is essential. In this Letter we note the need for an additional radiative correction to the Gamow-Teller form factor in allowed decays. It concerns a combination of electrostatic final state interactions and QCD-induced currents. We review the basic derivation and report analytical results. Due to differences in their theoretical treatment in the literature, effects on the neutron and mirror systems are distinct. Significant consequences appear for a comparison of the former with lattice QCD, while changes occur in the $|V_{ud}|$ extraction in the latter. We discuss new limits on right-handed currents and provide a new value for $|V_{ud}|$ from mirror decays.

   ↳ nucl-thnucl-ex16 citations
7. 07*

   J/$\psi$ production as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 5.02 TeV with ALICE

   Anisa Khatun (for the ALICE collaboration)🇮🇳

   The relative J/$\psi$ yields as a function of relative charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 5.02 TeV, measured at forward rapidity, are investigated for the first time. A linear increase of the relative J/$\psi$ yield with respect to multiplicity is observed. A comparison of the findings of the present work with the available ALICE measurements obtained in pp collisions at $\sqrt{s}$ = 13 TeV at forward and mid-rapidity indicates that the increase of J/$\psi$ with multiplicity is independent of energy but exhibits a strong dependence on the rapidity gap between the J/$\psi$ and multiplicity measurements. The results are compared with theoretical model calculations.

   ↳ hep-exnucl-exSpringer Proc.Phys.(2021)·9 citations
8. 08*

   Nuclear-modification factor of charged hadrons at forward and backward rapidity in $p$$+$Al and $p$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

   C. Aidala · Y. Akiba · M. Alfred · V. Andrieux · N. Apadula · H. Asano · B. Azmoun · V. Babintsev · N.S. Bandara · K.N. Barish · S. Bathe · A. Bazilevsky and 292 other authors

   The PHENIX experiment has studied nuclear effects in $p$$+$Al and $p$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV on charged hadron production at forward rapidity ($1.4<\eta <2.4$, $p$-going direction) and backward rapidity ($-2.2<\eta <-1.2$, $A$-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central $p$$+$Al and $p$$+$Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in $p$+$p$ collisions. The magnitude of enhancement at backward rapidity is larger in $p$$+$Au collisions than in $p$$+$Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.

   ↳ hep-exnucl-exPRC(2020)·33 citations
9. 09*

   Collectivity in small systems measured with PHENIX at RHIC

   Tamas Novak (for the PHENIX Collaboration)🇭🇺

   In this paper we show azimuthal particle correlations in three different small-system collisions with different intrinsic initial geometries. The simultaneous constraints of $v_2$ and $v_3$ in $p/d{/}^3$He$+$Au collisions definitively demonstrate that the $v_n$'s are correlated to the initial geometry. In addition, we find that hydrodynamical models which include QGP formation describe simultaneouly the elliptic and triangular flow data in a statistically acceptable manner in all three systems.

   ↳ hep-exnucl-ex0 citations
10. 10*

    Prompt $J/\psi$-pair production at the LHC: impact of loop-induced contributions and of the colour-octet mechanism

    Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇫🇷 · Nodoka Yamanaka🇫🇷 · Yu-Jie Zhang🇨🇳

    Prompt double-$J/\psi$ production at high-energy hadron colliders can be considered as a golden channel to probe double parton scatterings (DPS) --in particular to study gluon-gluon correlations inside the proton-- and, at the same time, to measure the distribution of linearly-polarised gluons inside the proton. Such studies however require a good control of both single and DPS in the respective regions where they are carried out. In this context, we have critically examined two mechanisms of single parton scatterings (SPS) that may be kinematically enhanced where DPS are thought to be dominant, even though they are either at higher orders in the strong-coupling or velocity expansion. First, we have considered a gauge-invariant and infrared-safe subset of the loop-induced contribution via Colour-Singlet (CS) transitions. We have found it to become the leading CS SPS contributions at large rapidity separation, yet too small to account for the data without invoking the presence of DPS yields. Second, we have surveyed the possible Colour-Octet (CO) contributions using both old and up-to-date non-perturbative long distance matrix elements (LDMEs). We have found that the pure CO yields crucially depend on the LDMEs. Among all the LDMEs we used, only two result into a visible modification of the NRQCD (CS+CO) yield, but only in two kinematical distributions measured by ATLAS, those of the rapidity separation and of the pair invariant mass. These modifications however do not impact the control region used for their DPS study.

    ↳ hep-phhep-exnucl-exnucl-thEPJC(2019)·29 citations
11. 11*

    Ab initio Gamow in-medium similarity renormalization group with resonance and continuum

    B. S. Hu🇨🇳 · Q. Wu🇨🇳 · Z. H. Sun🇨🇳 · F. R. Xu🇨🇳

    We have developed a novel ab initio Gamow in-medium similarity renormalization group (Gamow IMSRG) in the complex-energy Berggren framework. The advanced Gamow IMSRG is capable of describing the resonance and nonresonant continuum properties of weakly bound and unbound nuclear many-body systems. As test grounds, carbon and oxygen isotopes have been calculated with chiral two- and three-nucleon forces from the effective field theory. Resonant states observed in the neutron-dripline 24O are well reproduced. The halo structure of the known heaviest Borromean nucleus 22C is clearly seen by calculating the density distribution in which the continuum s channel plays a crucial role. Furthermore, we predict low-lying resonant excited states in 22C. The Gamow IMSRG provides tractable ab initio calculations of weakly bound and unbound open quantum systems.

    ↳ nucl-thnucl-exPRC(2019)·42 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.