Fri·Sep 1, 2017Friday·September 1, 2017

1. 01*

   Measurement of the splitting function in pp and PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV

   CMS Collaboration

   Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 GeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions. The measurements are compared to various predictions from event generators and analytical calculations.

   nucl-exhep-exPRL(2018)·207 citations
2. 02*

   Differential cross section and photon beam asymmetry for the gamma p -> pi+ n reaction at forward pi+ angles at Egamma=1.5-2.95 GeV

   H. Kohri🇯🇵 · S.Y. Wang🇹🇼 · S.H. Shiu🇹🇼 · W.C. Chang🇹🇼 · Y. Yanai🇯🇵 · D.S. Ahn🇯🇵 · J.K. Ahn🇰🇷 · J.Y. Chen🇹🇼 · S. Date🇯🇵 · H. Ejiri🇯🇵 · H. Fujimura🇯🇵 · M. Fujiwara🇯🇵 and 37 other authors

   Differential cross sections and photon beam asymmetries for the gamma p -> pi+ n reaction have been measured for 0.6<cos(theta)<1 and Egamma=1.5-2.95 GeV at SPring-8/LEPS. The cross sections monotonically decrease as the photon beam energy increases for 0.6<cos(theta)<0.9. However, the energy dependence of the cross sections for 0.9<cos(theta)<1 and Egamma=1.5-2.2 GeV (W=1.9-2.2 GeV) is different, which may be due to a nucleon or Delta resonance. The present cross sections agree well with the previous cross sections measured by other groups and show forward peaking, suggesting significant t-channel contributions in this kinematical region. The asymmetries are found to be positive, which can be explained by rho-exchange in the t-channel. Large positive asymmetries in the small |t| region, where the rho-exchange contribution becomes small, could be explained by introducing pi-exchange interference with the s-channel.

   nucl-exPRC(2018)·13 citations
3. 03*

   New limits on $2\epsilon$, $\epsilon {\beta }^{+}$ and $2{\beta }^{+}$ decay of ${}^{136}$Ce and ${}^{138}$Ce with deeply purified cerium sample

   P. Belli🇮🇹 · R. Bernabei🇮🇹 · R.S. Boiko🇺🇦 · F. Cappella🇮🇹 · R. Cerulli🇮🇹 · F.A. Danevich🇺🇦 · A. Incicchitti🇮🇹 · B.N. Kropivyansky🇺🇦 · M. Laubenstein🇮🇹 · V.M. Mokina🇺🇦 · O.G. Polischuk🇺🇦 · V.I.Tretyak🇺🇦

   A search for double electron capture ($2\epsilon$), electron capture with positron emission ($\epsilon {\beta }^{+}$), and double positron emission $2{\beta }^{+}$) in ${}^{136}$Ce and ${}^{138}$Ce was realized with a 465 cm${}^3$ ultra-low background HP Ge $\gamma$ spectrometer over 2299 h at the Gran Sasso underground laboratory. A 627 g sample of cerium oxide deeply purified by liquid-liquid extraction method was used as a source of $\gamma$ quanta expected in double $\beta$ decay of the cerium isotopes. New improved half-life limits were set on different modes and channels of double $\beta$ decay of ${}^{136}$Ce and ${}^{138}$Ce at the level of $T_{1/2}>10^{17}-10^{18}$ yr.

   nucl-exEPJA(2017)·15 citations
4. 04*

   New results on collectivity with CMS

   Jovan Milosevic (on behalf of the CMS Experiment)🇷🇸

   Nonlinear response coefficients of higher-order anisotropy harmonics for charged particles are measured in PbPb collisions at 2.76 and 5.02 TeV as a function of transverse momentum and collision centrality. The nonlinear response coefficients are obtained from $v_n$ harmonics measured with respect to their own plane and the mixed harmonics. Additionally, at 5.02 TeV PbPb collisions, a significant negative skewness is observed by a fine splitting between $v_2\{4\}$ and $v_2\{6\}$ cumulants. The elliptic flow skewness is measured up to 60\% centrality. The results are compared with hydrodynamic models with different shear viscosity to entropy density ratios and initial conditions.

   nucl-ex0 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.