Observation of polarization in bottomonium production at square root of s = 38.8 GeV

C N Brown; T C Awes; M E Beddo; M L Brooks; J D Bush; T A Carey; T H Chang; W E Cooper; C A Gagliardi; G T Garvey; D F Geesaman; E A Hawker; X C He; L D Isenhower; D M Kaplan; S B Kaufman; P N Kirk; D D Koetke; G Kyle; D M Lee; W M Lee; M J Leitch; N Makins; P L McGaughey; J M Moss; B A Mueller; P M Nord; V Papavassiliou; B K Park; J C Peng; G Petitt; P E Reimer; M E Sadler; W E Sondheim; P W Stankus; T N Thompson; R S Towell; R E Tribble; M A Vasiliev; J C Webb; J L Willis; D K Wise; G R Young; FNAL E866/NuSea Collaboration

doi:10.1103/PhysRevLett.86.2529

Observation of polarization in bottomonium production at square root of s = 38.8 GeV

Phys Rev Lett. 2001 Mar 19;86(12):2529-32. doi: 10.1103/PhysRevLett.86.2529.

Affiliation

¹ Fermi National Laboratory, Argonne, IL 60439, USA.

PMID: 11289972
DOI: 10.1103/PhysRevLett.86.2529

Abstract

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.