A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 pb À1 of data recorded at ffiffi ffi s p ¼ 7 TeV by the CMS detector at the LHC. The left-handed, right-handed, and longitudinal polarization fractions (f L , f R , and f 0 , respectively) of W bosons with transverse momenta larger than 50 GeV are determined by using decays to both electrons and muons. The muon final state yields the most precise measurement: The measurement of the kinematic properties of W bosons produced at hadron colliders provides a stringent test of perturbative quantum chromodynamics (QCD) calculations as well as being an important prerequisite to searches for physics beyond the standard model. The pp collisions at the Large Hadron Collider (LHC) offer both a new environment and a higher energy to study W bosons with large transverse momenta recoiling against several energetic jets. The sizable production cross section results in significant samples of W bosons, while the nature of the initial state leads to an enhancement of the quark-gluon contribution to W þ jet production when compared to the Tevatron p " p collider, where quark-gluon and antiquarkgluon processes contribute equally. This dominance of quark-gluon initial states, along with the V-A nature of the coupling of the W boson to fermions, implies that at the LHC W bosons with high transverse momenta are expected to exhibit a sizable left-handed polarization [1,2]. A significant asymmetry in the transverse momentum spectra of the neutrino and charged lepton from subsequent leptonic W decays is therefore expected. This Letter reports the first measurement of the polarization of W bosons with large transverse momenta ( > 50 GeV) at the LHC, using a data sample of pp collisions corresponding to an integrated luminosity of 36 AE 1:4 pb À1 at a center-of-mass energy of 7 TeV, recorded with the Compact Muon Solenoid (CMS) detector.We measure the polarization of the W boson in the helicity frame, where the polar angle ( à ) of the charged lepton from the decay in the W rest frame is measured with respect to the boson flight direction in the laboratory frame. The azimuthal angle ( à ) is defined to be zero for the proton beam which has the smaller à in the boson rest frame. The cross section for W production at a hadron collider with a subsequent leptonic decay, dN=d, is given bywhere the coefficients A i (i ¼ 0; . . . ; 4) depend on the W boson charge, transverse momentum, and rapidity and make up the elements of the polarization density matrix. Integrating Eq. (1) over à yieldsThe fractions of left-handed, right-handed, and longitudinal W bosons (f L , f R , and f 0 , respectively) are related to the parameters A i by A AE 0 / f AE 0 and A AE 4 / Çðf AE L À f AE R Þ, where the superscripts relate to the W boson charge and by definition f i > 0 and f L þ f R þ f 0 ¼ 1. A priori, the values of the f i parameters are not expected to be the same for both charges, since for partons, which carry a l...

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The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements.

Using 448.0 × 10 6 ψ(3686) events collected with the BESIII detector, an amplitude analysis is performed for ψ(3686) → γχc1, χc1 → ηπ + π − decays. The most dominant two-body structure observed is a0 (980) ± π ∓ ; a0(980) ± → ηπ ± . The a0(980) line shape is modeled using a dispersion relation, and a significant non-zero a0(980) coupling to the η ′ π channel is measured. We observe χc1 → a2(1700)π production for the first time, with a significance larger than 17σ. The production of mesons with exotic quantum numbers, J P C = 1 −+ , is investigated, and upper limits for the branching fractions χc1 → π1(1400) ± π ∓ , χc1 → π1(1600) ± π ∓ , and χc1 → π1(2015) ± π ∓ , with subsequent π1(X) ± → ηπ ± decay, are determined.