ϒ(nS)andχb(nP)productio

Abstract

Υ(nS) and χ b (nP ) (n=1,2,3) production at the LHC is studied at next-to-leading order in αs in nonrelativistic QCD. Feeddown contributions from higher χ b and Υ states are all considered for lower Υ cross sections and polarizations. The long distance matrix elements (LDMEs) are extracted from the yield data, and then used to make predictions for the Υ(nS) polarizations, which are found to be consistent with the measured polarization data within errors. In particular, the Υ(3S) polarization puzzle can be understood by a large feeddown contribution from χ b (3P ) states. Our results may provide a good description for both cross sections and polarizations of prompt Υ(nS) and χ b (nP ) production at the LHC.

Hadron Physics Experimental Overview

“…energy of 4.26 GeV. The cross section is measured to be ð62:9 AE 1:9 AE 3:7Þ pb, which agrees with the existing results from the BABAR [5] …”

“…The same behavior was also observed, for example, for the production of cc or b-hadrons [3]. Precise comparison with the expectations awaits for the update of the theoretical models [5]. The recent study of bb production from the study of b-hadron semileptonic decays at 13 TeV shows some tension with theoretical predictions, especially at low η [6], which call for further investigation.…”

Measurement of the Y(nS) polarizations in pp collisions at s = 7 $$ \sqrt{s}=7 $$ and 8 TeV

“…According to the NRQCD factorization approach [4], these matrix elements are universal constants which are independent of the short-time production processes, and need to be determined from data. Calculations based on the colour-singlet model [6][7][8] show good agreement [9][10][11][12][13][14] with the experimental data [15][16][17][18][19][20][21][22] for production cross-sections and the shapes of the transverse momentum spectra. However, this approach fails to describe the spin-alignment (usually labelled as polarization) of S-wave charmonium states [23,24].…”

Heavy flavour production at LHCb

“…Transverse momentum (left) and rapidity (right) dependences. Prediction curves obtained using the NRQCD [18] and CO model [19,20,21] calculations are shown on the left and right plots, respectively. regime p T < 30 GeV/c 2 , 2.0 < y < 4.5 [17].…”

“…Table 1 summarizes the results. Similarly to the J/ψ case, the ϒ(nS) production cross-section ratios R 8/7 are compared to the NRQCD [18] and Colour Octet (CO) model calculations in Fig. 2 [19,20,21].…”