Abstract
The measurement of the deuteron and anti-deuteron production in the rapidity range −1<y<0 as a function of transverse momentum and event multiplicity in p–Pb collisions at sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of-flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and Λ particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare He3 and He‾3 nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1<y<0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and He3, normalised by the spin degeneracy factor, follow an exponential decrease with mass number.
Highlights
The energy densities reached in the collisions of ultrarelativistic particles lead to a significant production of complex(hyper-)nuclei
The results presented here are based on a low pile-up p–Pb data ning scaammpplaeigcnolaletc√tedsNwN =ith5t.0h2e
The value of B2 is computed as a function of event multiplicity and transverse momentum as the ratio between the deuteron yield measured at pT = pT,d and the square of the proton yield at pT,p = 0.5pT,d
Summary
The energy densities reached in the collisions of ultrarelativistic particles lead to a significant production of complex (anti-)(hyper-)nuclei. In addition to the evolution of the integrated d/p ratio for various multiplicity classes, the question whether the transverse momentum distribution of deuterons is consistent with a collective radial expansion together with the non-composite hadrons is of particular interest Such behaviour has been observed for light nuclei in Pb–Pb collisions [3,5]. The presence of collective effects in p–Pb collisions at LHC energies has recently been supported by several experimental findings (see for instance [16,17,18,19,20,21,22] and recent reviews in [23,24]) These include a clear mass ordering of the mean transverse momenta of light flavoured hadrons in p–Pb collisions as expected from hydrodynamical models [18]
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