First measurement of prompt and non-prompt D*+ vector meson spin alignment in pp collisions at root s=13 Tev

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21340%2F23%3A00373762" target="_blank" >RIV/68407700:21340/23:00373762 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1016/j.physletb.2023.137920" target="_blank" >https://doi.org/10.1016/j.physletb.2023.137920</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.physletb.2023.137920" target="_blank" >10.1016/j.physletb.2023.137920</a>

Result language

angličtina

Original language name

First measurement of prompt and non-prompt D*+ vector meson spin alignment in pp collisions at root s=13 Tev

Original language description

This letter reports the first measurement of spin alignment, with respect to the helicity axis, for D*(+) vector mesons and their charge conjugates from charm-quark hadronisation (prompt) and from beauty-meson decays (non-prompt) in hadron collisions. The measurements were performed at midrapidity (vertical bar y vertical bar < 0.8) as a function of transverse momentum (p(T)) in proton-proton (pp) collisions collected by ALICE at the centre-of-mass energy root s= 13TeV. The diagonal spin density matrix element rho(00) of D*(+) mesons was measured from the angular distribution of the D*(+) -> D-0(-> K- pi(+))pi(+) decay products, in the D*(+) rest frame, with respect to the D*(+) momentum direction in the pp centre of mass frame. The rho(00) value for prompt D*(+) mesons is consistent with 1/3, which implies no spin alignment. However, for nonprompt D*(+) mesons an evidence of rho(00) larger than 1/3 is found. The measured value of the spin density element is rho(00)= 0.455 +/- 0.022(stat.) +/- 0.035(syst.) in the 5 < p(T) < 20GeV/c interval, which is consistent with a Pythia 8 Monte Carlo simulation coupled with theEvtGenpackage, which implements the helicity conservation in the decay of D*+ meson from beauty mesons. In non-central heavy-ion collisions, the spin of the D*(+) mesons may be globally aligned with the direction of the initial angular momentum and magnetic field. Based on the results for pp collisions reported in this letter it is shown that alignment of non-prompt D*(+) mesons due to the helicity conservation coupled to the collective anisotropic expansion may mimic the signal of global spin alignment in heavy-ion collisions.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10303 - Particles and field physics

Project

<a href="/en/project/LM2018104" target="_blank" >LM2018104: Research Infrastructure for experiments at CERN</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2023

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Physics Letters B

ISSN

0370-2693

e-ISSN

1873-2445

Volume of the periodical

846

Issue of the periodical within the volume

Nov

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

15

Pages from-to

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UT code for WoS article

001170331200001

EID of the result in the Scopus database

2-s2.0-85173191408