Charmonium production in pNe collisions at $$\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5$$ s NN = 68.5 GeV

Abstract

Abstract The measurement of charmonium states produced in proton-neon (

$$p\text {Ne}$$

p Ne

) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of

$${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$

J

/

ψ

and

$$\psi {(2S)}$$

ψ

( 2 S )

mesons is studied with a beam of 2.5

$$\mathrm{\,Te\hspace{-1.00006pt}V}$$

Te

V

protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy

$$\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5\mathrm{\,Ge\hspace{-1.00006pt}V} $$

s

NN

= 68.5

Ge

V

. The data sample corresponds to an integrated luminosity of

$$21.7\pm 1.4 $$

21.7 ± 1.4

nb

$$^{-1}$$

- 1

. The

$${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$

J

/

ψ

and

$$\psi {(2S)}$$

ψ

( 2 S )

hadrons are reconstructed in

$$\mu ^+$$

μ +

$$\mu ^-$$

μ -

final states. The

$${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$

J

/

ψ

production cross-section per target nucleon in the centre-of-mass rapidity range

$$y^\star \in [-2.29, 0]$$

y ⋆

∈

[ - 2.29 , 0 ]

is found to be

$$506 \pm 8 \pm 46 \text { nb/nucleon}$$

506 ± 8 ± 46

nb/nucleon

. The ratio of

$${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$

J

/

ψ

and

$$D^0$$

D 0

cross-sections is evaluated to

$$(1.06 \pm 0.02 \pm 0.09)\%$$

( 1.06 ± 0.02 ± 0.09 ) %

. The

$$\psi {(2S)}$$

ψ

( 2 S )

to

$${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$

J

/

ψ

relative production rate is found to be

$$(1.67 \pm 0.27\pm 0.10)\%$$

( 1.67 ± 0.27 ± 0.10 ) %

in good agreement with other measurements involving beam and target nuclei of similar sizes.