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Paper   IPM / Particles / 11881
School of Particles and Accelerator
  Title:   Measurement of the Polarization of W Bosons with Large Transverse Momenta in W+Jets Events at the LHC
1.  Hessamadin Arfaei
2.  Hamed Bakhshiansohi
3.  Seyed Mohsen Etesami
4.  Ali Fahim
5.  Majid Hashemi
6.  Abideh Jafari
7.  Mohsen Khakzad
8.  A Mohammadi
9.  Mojtaba Mohammadi Najafabadi
10.  Saeid Paktinat Mehdiabadi
11.  Batool Safarzadeh
12.  Maryam Zeinali
  Status:   Published
  Journal: Phys. Rev. Lett.
  No.:  021802
  Vol.:  107
  Year:  2011
  Supported by:  IPM
A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 pb1 of data recorded at sqrt(s) = 7 TeV by the CMS detector at the LHC. The left-handed, righthanded and longitudinal polarization fractions ( fL, fR, f0) of W bosons with transverse momenta larger than 50 GeV are determined using decays to both electrons and muons. The muon final state yields the most precise measurement, ( fL - fR)=0.240  0.036 (stat.)  0.031 (syst.) and f 0 = 0.183  0.087 (stat.)  0.123 (syst.) for negatively charged W bosons, and ( fL - fR)+ = 0.310  0.036 (stat.)  0.017 (syst.) and f+0 = 0.171  0.085 (stat.)  0.099 (syst.) for positively charged W bosons. This establishes, for the first time, that W bosons produced in pp collisions with large transverse momenta are predominantly left-handed, as expected in the standard model

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