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

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10303 - Particles and field physics

Projekt

<a href="/cs/project/LM2018104" target="_blank" >LM2018104: Výzkumná infrastruktura pro experimenty v CERN</a><br>

Návaznosti

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

Rok uplatnění

2023

Kód důvěrnosti údajů

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

Název periodika

Physics Letters B

ISSN

0370-2693

e-ISSN

1873-2445

Svazek periodika

846

Číslo periodika v rámci svazku

Nov

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

15

Strana od-do

—

Kód UT WoS článku

001170331200001

EID výsledku v databázi Scopus

2-s2.0-85173191408