Thu·Jun 25, 2015Thursday·June 25, 2015

1. 01*

   Centrality dependence of the nuclear modification factor of charged pions, kaons, and protons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   Transverse momentum ($p_{\mathrm{T}}$) spectra of pions, kaons, and protons up to $p_{\mathrm{T}}=20$ GeV/$c$ have been measured in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV using the ALICE detector for six different centrality classes covering 0-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at $p_{\mathrm{T}}\approx 3$ GeV/$c$ in central Pb-Pb collisions that decreases towards more peripheral collisions. For $p_{\mathrm{T}}>10$ GeV/$c$, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For $p_{\mathrm{T}}<10$ GeV/$c$, the data provide important constraints for models aimed at describing the transition from soft to hard physics.

   nucl-exhep-exPRC(2016)·210 citations
2. 02*

   Nuclear shadowing in photoproduction of $\rho$ mesons in ultraperipheral nucleus collisions at RHIC and the LHC

   L. Frankfurt (Tel Aviv U.)🇮🇱 · V. Guzey (PNPI, Gatchina)🇷🇺 · M. Strikman (Penn State U.)🇺🇸 · M. Zhalov (PNPI, Gatchina)🇷🇺

   We argue that with an increase of the collision energy, elastic photoproduction of $\rho$ mesons on nuclei becomes affected by the significant cross section of photon inelastic diffraction into large masses, which results in the sizable inelastic nuclear shadowing correction to ${\sigma }_{\gamma A\to \rho A}$ and the reduced effective $\rho$-nucleon cross section. We take these effects into account by combining the vector meson dominance model, which we upgrade to include the contribution of high-mass fluctuations of the photon according to QCD constraints, and the Gribov-Glauber approximation for nuclear shadowing, where the inelastic nuclear shadowing is included by means of cross section fluctuations. The resulting approach allows us to successfully describe the data on elastic $\rho$ photoproduction on nuclei in heavy ion UPCs in the $7\mathrm{GeV}<W_{\gamma p}<46$ GeV energy range and to predict the value of the cross section of coherent $\rho$ photoproduction in Pb-Pb UPCs at $\sqrt{s_{NN}}=5.02$ TeV in Run 2 at the LHC, $d{\sigma }_{PbPb\to \rho PbPb}(y=0)/dy=560\pm 25$ mb.

   ↳ hep-phhep-exnucl-exPLB(2016)·64 citations
3. 03*

   Study the vibration and dynamic response of the dipole girder system for CSNS/RCS

   Liu Renhong🇨🇳 · Wang Min🇨🇳 · Zhang JunSong🇺🇸 · Wang GuangYuan🇨🇳

   China Spallation Neutron Source is a high intensity proton accelerator based facility, and its accelerator complex includes two main parts an H- linac and a rapid cycling synchrotron. The RCS accumulates the 80MeV proton beam, and accelerates it to 1.6GeV, with a repetition rate of 25Hz. The dipole of the CSNS RCS is operated at a 25 Hz sinusoidal alternating current which causes severe vibrate. The vibration will influence the long term safety and reliable operation of the magnet. The dipole of the CSNS RCS is an active vibration equipment which is different from the ground vibration accelerator. It is very important to design and study the dynamic characteristics of the dipole girder system. This paper takes the dipole and girder as a specific model system, a method for studying the dynamic characteristics of the system is put forward by combining theoretical calculation with experimental testing. The modal parameters with and without vibration isolator of the dipole girder system are obtain through ANSYS simulation and testing. Then the dynamic response of the system is calculated with modal analysis and vibration testing data. The dipole girder takes four-point support system which maybe appears over constrained in the progress of adjustment. The dynamic characteristics and dynamic response of the three point girder system were studied with the same method.

   ↳ physics.acc-phnucl-ex0 citations
4. 04*

   New parton distribution functions from a global analysis of quantum chromodynamics

   Sayipjamal Dulat🇨🇳 · Tie Jiun Hou🇺🇸 · Jun Gao🇺🇸 · Marco Guzzi🇬🇧 · Joey Huston🇺🇸 · Pavel Nadolsky🇺🇸 · Jon Pumplin🇺🇸 · Carl Schmidt🇺🇸 · Daniel Stump🇺🇸 · C. P. Yuan🇺🇸

   We present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various ${\alpha }_s$ values and additional sets in general-mass variable flavor number (GM-VFN) schemes, to deal with heavy partons, with up to 3, 4, and 6 active flavors.

   ↳ hep-phhep-exnucl-exPRD(2016)·2108 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.