Fri·Mar 6, 2015Friday·March 6, 2015

1. 01*

   The Structure of the Nucleon: Elastic Electromagnetic Form Factors

   V. Punjabi🇺🇸 · C.F. Perdrisat🇺🇸 · M.K. Jones🇺🇸 · E.J. Brash🇺🇸 · C.E. Carlson🇺🇸

   Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.

   nucl-exnucl-thEPJA(2015)·262 citations
2. 02*

   Transverse momentum and multiplicity fluctuations in the Be+Be energy scan from NA61/SHINE

   Tobiasz Czopowicz (for the NA61/SHINE Collaboration)🇵🇱

   The NA61/SHINE experiment aims to discover the Critical Point of strongly interacting matter and study the properties of the onset of deconfinement. These goals are to be achieved by per- forming a two-dimensional phase diagram ($T-{\mu }_B$) scan by measurements of hadron production properties in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of col- lision energy and system size. Close to the Critical Point an increase of fluctuations is predicted. This contribution presents preliminary results on transverse momentum and multiplicity fluctua- tions expressed in terms of strongly intensive quantities from the Be+Be energy scan. The data are fully corrected for contributions from non-target interactions. The Be+Be results are compared with NA61/SHINE measurements from the p+p energy scan, with NA49 results from central Pb+Pb collisions as well as with model predictions.

   nucl-exPoS(2015)·17 citations
3. 03*

   Evidence for transverse momentum and pseudorapidity dependent event plane fluctuations in PbPb and pPb collisions

   CMS Collaboration

   A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of pt and eta of both particles, and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at sqrt(s[NN]) = 2.76 TeV and pPb collisions at sqrt(s[NN]) = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle pt and eta. When measured with particles of different pt, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different eta. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very high-multiplicity pPb collisions. The eta-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions.

   nucl-exhep-exPRC(2015)·282 citations
4. 04*

   Charge symmetry breaking in $\Lambda$ hypernuclei revisited

   Avraham Gal🇮🇱

   The large charge symmetry breaking (CSB) implied by the $\Lambda$ binding energy difference $\Delta B_{\Lambda }^4(0_{g.s.}^{+})\equiv B_{\Lambda }{(}_{\Lambda }^4$He)$-$$B_{\Lambda }{(}_{\Lambda }^4$H) = 0.35$\pm$0.06 MeV of the $A=4$ mirror hypernuclei ground states, determined from emulsion studies, has defied theoretical attempts to reproduce it in terms of CSB in hyperon masses and in hyperon-nucleon interactions, including one pion exchange arising from $\Lambda -{\Sigma }^0$ mixing. Using a schematic strong-interaction $\Lambda N\leftrightarrow \Sigma N$ coupling model developed by Akaishi and collaborators for $s$-shell $\Lambda$ hypernuclei, we revisit the evaluation of CSB in the $A=4$ $\Lambda$ hypernuclei and extend it to $p$-shell mirror $\Lambda$ hypernuclei. The model yields values of $\Delta B_{\Lambda }^4(0_{g.s.}^{+})\sim 0.25$ MeV. Smaller size and mostly negative $p$-shell binding energy differences are calculated for the $A=7-10$ mirror hypernuclei, in rough agreement with the few available data. CSB is found to reduce by almost 30 keV the 110 keV ${}_{\Lambda }^{10}$B g.s. doublet splitting anticipated from the hyperon-nucleon strong-interaction spin dependence, thereby explaining the persistent experimental failure to observe the $2_{\mathrm{exc}}^{-}\to 1_{g.s.}^{-}$ $\gamma$-ray transition.

   ↳ nucl-thhep-phnucl-exPLB(2015)·74 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.