Wed·Sep 5, 2018Wednesday·September 5, 2018

1. 01*

   Experimental search for the bound state singlet deuteron in the radiative n-p capture

   T. Belgya🇭🇺 · S.B. Borzakov🇷🇺 · M. Jentschel🇫🇷 · B. Maroti · Yu.N. Pokotilovski🇷🇺 · L. Szentmiklosi🇭🇺

   We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The predicted energy of this metastable level is in vicinity of the deuteron disintegration threshold. This state should manifest itself in two-photon transition following thermal neutron capture by protons. The experiment consists in the search for the second gamma-ray in the cascade through a high statistics measurement of $\gamma$-ray spectra after cold neutron capture by hydrogen nuclei. The upper limit $2\mu$b (2$\sigma$ level) is obtained for the cross section of the singlet deuteron production with the bound energy in the range 10-125 keV.

   nucl-exPRC(2019)·2 citations
2. 02*

   Recent STAR Measurements to Constrain the Polarized Gluon Distribution Function of the Proton

   Amilkar Quintero (for the STAR collaboration)🇺🇸

   The STAR experiment has been studying the spin structure of the proton, using the unique high-energy polarized proton collider, the Relativistic Heavy Ion Collider (RHIC). The kinematic coverage at STAR allows accessing gluons because quark-gluon and gluon-gluon scatterings dominate particle production at low and medium transverse momenta. The polarized gluon distribution function can be constrained by measuring the longitudinal double-spin asymmetry ($A_{LL}$) of jet production and neutral pions. Global QCD analyses of polarized parton distribution functions, which include the 2009 $A_{LL}$ STAR results for inclusive jet production at $\sqrt{s}=200$ GeV, provide evidence of a non-zero gluon polarization in the measured range of partonic momentum fraction $x>0.05$. We present the status of the latest measurements of $A_{LL}$ at STAR, for inclusive jet and dijet production at $\sqrt{s}=510$ GeV and 200 GeV collected in 2013 and 2015 respectively, both at mid-rapidity ($|\eta |<0.9$). The large data sample taken during these years will improve the precision of our knowledge about the proton spin structure while the increased center of mass energy allows probing the polarized gluon distribution function at smaller partonic momentum fraction. Furthermore, we present measurements of $A_{LL}$ for neutral pions at forward rapidity ($2.65<\eta <3.9$) collected during 2012 and 2013 that also allow reaching lower partonic momentum fraction. We compare these measurements with the latest global analyses.

   nucl-exPoS(2018)·3 citations
3. 03*

   Production of pions, kaons and protons in Xe--Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV

   Simone Ragoni (for the ALICE Collaboration)🇮🇹

   In late 2017, the ALICE experiment recorded a data sample of Xe--Xe collisions at the unprecedented energy in A--A systems of $\sqrt{s_{\mathrm{NN}}}=5.44\text{ TeV}$. The $p_{\mathrm{T}}$ spectra at mid-rapidity ($|y|<0.5$) of pions, kaons and protons are presented. The preliminary $p_{\mathrm{T}}$ spectra are obtained by combining independent analyses with the Inner Tracking System (ITS), the Time Projection Chamber (TPC), and the Time-Of-Flight (TOF) detectors. This paper focuses on the details of the analysis performed with TOF and in particular on the performance implications of the special Xe--Xe run conditions. The peculiarity of this data set comes from the experimental conditions: because of the lower magnetic field of the ALICE solenoid ($B=0.2\text{ T}$, lower than the nominal $0.5\text{ T}$) we expect to explore a $p_{\mathrm{T}}$ region unattainable before. A comparison between the yields at different centrality bins will also be provided.

   ↳ hep-exnucl-exPoS(2018)·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.