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Multiplicity dependence of (anti-)deuteron production in pp collisions at $\sqrt{s}$ = 7 TeV

The collaboration
Phys.Lett. B794 (2019) 50-63, 2019

Abstract (data abstract)
In this letter, the production of deuterons and anti-deuterons in pp collisions at $\sqrt{s}$ = 7 TeV is studied as a function of the charged-particle multiplicity density at mid-rapidity with the ALICE detector at the LHC. Production yields are measured at mid-rapidity in five multiplicity classes and as a function of the deuteron transverse momentum (pT). The measurements are discussed in the context of hadron-coalescence models. The coalescence parameter B2, extracted from the measured spectra of (anti-)deuterons and primary (anti-)protons, exhibits no significant pT-dependence for pT < 3 GeV/c, in agreement with the expectations of a simple coalescence picture. At fixed transverse momentum per nucleon, the B2 parameter is found to decrease smoothly from low multiplicity pp to Pb-Pb collisions, in qualitative agreement with more elaborate coalescence models. The measured mean transverse momentum of (anti-)deuterons in pp is not reproduced by the Blast-Wave model calculations that simultaneously describe pion, kaon and proton spectra, in contrast to central Pb-Pb collisions. The ratio between the pT-integrated yield of deuterons to protons, d/p, is found to increase with the charged-particle multiplicity, as observed in inelastic pp collisions at different centre-of-mass energies. The d/p ratios are reported in a wide range, from the lowest to the highest multiplicity values measured in pp collisions at the LHC.

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Fig. 2

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Transverse-momentum spectra of deuterons and anti-deuterons measured at mid-rapidity in V0M multiplicity class I+II

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Fig. 2

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Transverse-momentum spectra of deuterons and anti-deuterons measured at mid-rapidity in V0M multiplicity class III

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Fig. 2

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Transverse-momentum spectra of deuterons and anti-deuterons measured at mid-rapidity in V0M multiplicity class IV+V

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Fig. 2

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Transverse-momentum spectra of deuterons and anti-deuterons measured at mid-rapidity in V0M multiplicity class VI+VII

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Fig. 2

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Transverse-momentum spectra of deuterons and anti-deuterons measured at mid-rapidity in V0M multiplicity class VIII+IX+X

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Fig. 4

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Coalescence parameter $B_2$ of (anti-)deuterons vs. the transverse momentum per nucleon in V0M multiplicity class I+II

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Fig. 4

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Coalescence parameter $B_2$ of (anti-)deuterons vs. the transverse momentum per nucleon in V0M multiplicity class III

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Fig. 4

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Coalescence parameter $B_2$ of (anti-)deuterons vs. the transverse momentum per nucleon in V0M multiplicity class IV+V

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Fig. 4

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Coalescence parameter $B_2$ of (anti-)deuterons vs. the transverse momentum per nucleon in V0M multiplicity class VI+VII

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Fig. 4

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Coalescence parameter $B_2$ of (anti-)deuterons vs. the transverse momentum per nucleon in V0M multiplicity class VIII+IX+X

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Fig. 7

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Mean transverse momentum ($\langle p_T \rangle$) of (anti-)deuterons as a function of charged-particle multiplicity at mid-rapidity ($\langle dN_{ch}/d\eta \rangle_{|\eta|<0.5}$)

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Fig. 8

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Ratio between the $p_T$-integrated yield of deuterons and protons (d/p) as a function of charged-particle multiplicity at mid-rapidity (\$\langle dN_{ch}/d\eta...