Title: $b\overline{b}$ kinematic correlations in cold nuclear matter

Abstract

Background: The LHCb Collaboration has studied a number of kinematic correlations between $B$-hadron pairs through their subsequent decays to $J/\psi$ pairs in $p+p$ collisions at 7 and 8 TeV for four minimum values of the $J/\psi p_T$. Purpose: In this work, these measurements are compared to calculations of $b\overline{b}$ pairs and their hadronization and inclusive decays to $J/\psi J/\psi$ are compared to the same observables. Potential cold matter effects on the $b\overline{b}$ pair observables are discussed to determine which are most likely to provide insights about the system and why. Methods: The calculations, employing the exclusive HVQMNR code, assume the same intrinsic $k_T$-broadening and fragmentation as in prior work. The pair distributions presented by LHCb are calculated in this approach, both for the parent $b\overline{b}$ and the $J/\psi J/\psi$ pairs produced in their decays. The sensitivity of the results to the intrinsic $k_T$ broadening is shown. The theoretical uncertainties due to the $b$ quark mass and scale variations on both the initial $b\overline{b}$ pairs and the resulting $J/\psi$ pairs are also shown, as is the dependence of the results on the rapidity range of the measurement. Possible effects due to the presence of the nucleus are studied by increasing the size of the $k_T$ broadening and modifying the fragmentation function. Results: Good agreement with the LHCb data is found for all observables. The parent $b\overline{b}$ distributions are more sensitive to the $k_T$ broadening than are the final-state $J/\psi$ pairs. Conclusions: Next-to-leading order calculations with $k_T$ broadening, as in prior work, can describe all correlated observables. Multiple measurements of correlated observables are sensitive to different nuclear effects which can help distinguish between them.

Authors:

Vogt, R.

• Search DOE PAGES for author "Vogt, R."
• Search DOE PAGES for ORCID "0000-0002-0633-1260"
• Search orcid.org for ORCID "0000-0002-0633-1260"

Publication Date:

2020-02-18

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Nuclear Physics (NP)

Contributing Org.:

LHCb Collaboration

OSTI Identifier:

1600073

Alternate Identifier(s):

OSTI ID: 1608097

Report Number(s):

LLNL-JRNL-785319
Journal ID: ISSN 2469-9985; PRVCAN; 024910

Grant/Contract Number:  

AC52-07NA27344; SC0004014

Resource Type:

Published Article

Journal Name:

Physical Review C

Additional Journal Information:

Journal Name: Physical Review C Journal Volume: 101 Journal Issue: 2; Journal ID: ISSN 2469-9985

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS