Brown CN, Awes TC, Beddo ME, Brooks ML, Bush JD, Carey TA, Chang TH, Cooper WE, Gagliardi CA, Garvey GT, Geesaman DF, Hawker EA, He XC, Isenhower LD, Kaplan DM, Kaufman SB, Kirk PN, Koetke DD, Kyle G, Lee DM, Lee WM, Leitch MJ, Makins N, McGaughey PL, Moss JM, Mueller BA, Nord PM, Papavassiliou V, Park BK, Peng JC, Petitt G, Reimer PE, Sadler ME, Sondheim WE, Stankus PW, Thompson TN, Towell RS, Tribble RE, Vasiliev MA, Webb JC, Willis JL, Wise DK, Young GR. Observation of polarization in bottomonium production at square root of s = 38.8 GeV.
PHYSICAL REVIEW LETTERS 2001;
86:2529-2532. [PMID:
11289972 DOI:
10.1103/physrevlett.86.2529]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2000] [Indexed: 05/23/2023]
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.
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