Dönigus, Benjamin

Kalweit, Alexander

Martin, N.

GSI Repository

Deuteron production in Pb–Pb collisions measured with ALICE at the LHC∗B. Do¨nigus†1, A. Kalweit2, N. Martin3,4 for the ALICE Collaboration1Institut fu¨r Kernphysik, Goethe-Universita¨t Frankfurt, Frankfurt, Germany; 2European Organization for NuclearResearch (CERN), Geneva, Switzerland; 3ExtreMe Matter Institute EMMI and Research Division, GSIHelmhotzzentrum fu¨r Schwerionenforschung, Darmstadt, Germany; 4Institut fu¨r Kernphysik, Technische Universita¨tDarmstadt, Darmstadt, GermanyHeavy-ion collisions at the LHC give the opportunity tomeasure all known particles in higher abundances than itwas possible before, like for example light nuclei. Theseheavy particles are rarely produced, because the productionprobability decreases with increasing mass. But the energyregime reached at the LHC leads to large production prob-abilities even for these particles, as described for exam-ple by thermal models [1, 2]. The excellent performanceof the Time-Projection Chamber (TPC) [3] and the Time-Of-Flight detector (TOF) [4] allows for the clear identifi-cation of charged stable particles over a range of 0.15 to5 GeV/c in rigidity R = p/z, where p is the track mo-mentum and z is the charge number. The measurement ofdeuterons is affected by a large background, as for all nu-clei, coming from knockout from material. Rejection ofthis background is possible by restricting the distance-of-closest-approach (dca) of the track to the primary vertexin z-direction dcaz and then fitting the dcaxy distributionto extract the signal in the transverse momentum (pT) win-dow between 0.6 and 1.9 GeV/c (technique is described inmore detail in [6]). The deuterons are identified using onlythe specific energy loss (dE/dx) measurement in the TPCfor pT < 1.5GeV and combining the TPC and TOF in-formation for higher pT. A sample of deuteron selectedwithin a 3σ cut around the expected dE/dx value is ini-tially used to build the m2 −m2d-distribution, where md isthe deuteron mass and m is the mass measured with TOFusing m2 = p2/(γ2 − 1). Then, this distribution is fit-ted in pT intervals. The extracted yields are then efficiencyand acceptance corrected and the final spectra are shown inFigure 1 for five different collision centralities. The spectrashow a characteristic hardening with increasing centrality,qualitatively similar to proton spectra. To extract pT inte-grated yields the spectra in the different centrality bins arefitted by individual blast-wave distributions. The ratios ofthese yields with those of protons are shown in Figure 2 forfive different centralities. The measured ratio agrees wellwith the mean of the d/p and the d¯/p¯ from PHENIX [7],which is a fair comparison since the baryo-chemical poten-tial μB at the LHC is getting close to 0MeV [2].References[1] A. Andronic et al., Phys. Lett. B 697 (2011) 203[2] J. Cleymans et al., Phys. Rev. C 84 (2011) 054916∗Work supported by GSI, BMBF, Helmholtz Alliance HA216/EMMI,H-QM, and HGS-HIRe.† b.doenigus@gsi.deALI-PREL-51980 	    	  				Figure 1: Measured deuteron spectra at √sNN =2.76TeV for five different centralities. The linesthrough the measured points are individual blast-wavefits.ALI-PREL-51984~~ ~~ ~~ ~~ ~~ ~~ !#~~~~~~~~~~~~	~~~~~~~~" " " Figure 2: Deuteron-to-proton ratio over centralitycompared with the PHENIX measurement [7] ofdeuteron-to-proton ratio and the anti-deuteron-to-anti-proton ratio at √sNN = 200GeV.[3] J. Alme et al. (ALICE TPC Collaboration), Nucl. Instr.Meas. A 622 (2010) 316[4] K. Aamodt et al. (ALICE Collaboration), JINST 3 (2008)S08002[5] B. Do¨nigus (for the ALICE Collaboration), Nucl. Phys. A904-905 (2013) 457c[6] B. Abelev et al. (ALICE Collaboration), CERN-PH-EP-2013-019, (2013) arXiv:1303.0737v2 [hep-ex][7] S. S. Adler, Phys. Rev. Lett. 94 (2005) 122302GSI SCIENTIFIC REPORT 2013 NQM-ALICE-09doi:10.15120/GR-2014-1-NQM-ALICE-09 73

Deuteron production in Pb-Pb collisions measured with ALICE at the LHC

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Deuteron production in Pb-Pb collisions measured with ALICE at the LHC

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