Revisiting Scalar and Pseudoscalar Couplings with Nucleons

Certain dark matter interactions with nuclei are mediated possibly by a scalar or pseudoscalar Higgs boson. The estimation of the corresponding cross sections requires a correct evaluation of the couplings between the scalar or pseudoscalar Higgs boson and the nucleons. Progress has been made in two aspects relevant to this study in the past few years. First, recent lattice calculations show that the strange-quark sigma term $\sigma_s$ and the strange-quark content in the nucleon are much smaller than what are expected previously. Second, lattice and model analyses imply sizable SU(3) breaking effects in the determination on the axial-vector coupling constant $g_A^8$ that in turn affect the extraction of the isosinglet coupling $g_A^0$ and the strange quark spin component $\Delta s$ from polarized deep inelastic scattering experiments. Based on these new developments, we re-evaluate the relevant nucleon matrix elements and compute the scalar and pseudoscalar couplings of the proton and neutron. We also find that the strange quark contribution in both types of couplings is smaller than previously thought.Comment: 17 pages, Sec. II is revised and the pion-nucleon sigma term extracted from the scattering data is discussed. Version to appear in JHE

Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the pi- pi- pi+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data show a significant natural parity exchange production of a resonance with spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The resonant nature of this wave is evident from the mass-dependent phase differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2 is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged; version 3 updated authors, text shortened, data unchange

Hadron transverse momentum distributions in muon deep inelastic scattering at 160 GeV/c

Multiplicities of charged hadrons produced in deep inelastic muon scattering off a LiD target have been measured as a function of the DIS variables x , Q , W and the final state hadron variables p and z. The p distributions are fitted with a single exponential function at low values of p to determine the dependence of 〈p 〉 on x , Q , W and z. The z-dependence of 〈p 〉 is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons, 〈k 〉, as a function of x and Q in a leading order QCD parton model. 6 2 2 2 2 2 2 2 2 2 2 Bj T T T T Bj T ⊥ B

Hadron transverse momentum distributions in muon deep inelastic scattering at 160 GeV/c

Multiplicities of charged hadrons produced in deep inelastic muon scattering off a 6LiD target have been measured as a function of the DIS variables xBj , Q2, W2 and the final state hadron variables pT and z. The p2T distributions are fitted with a single exponential function at low values of p2T to determine the dependence of 〈p2T 〉 on xBj , Q2, W2 and z. The z-dependence of 〈p2T 〉 is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons, 〈k2⊥〉, as a function of xBj and Q2 in a leading order QCD parton model

Epidemiological applications of long-term stress in daily life.

The gluon polarisation in the nucleon has been determined by detecting charm production via D0 meson decay to charged K and \u3c0 in polarised muon scattering off a longitudinally polarised deuteron target. The data were taken by the COMPASS Collaboration at CERN between 2002 and 2006 and correspond to an integrated luminosity of 2.8 fb 121. The dominant underlying process of charm production is the photon\u2013gluon fusion to a_(c barc) pair. A leading order QCD approach gives an average gluon polarisation of _x= 120.49\ub10.27(stat)\ub10.11(syst) at a scale \u3bc^2 4813 (GeV/c)^2 and at an average gluon momentum fraction 480.11. The longitudinal cross-section asymmetry for D0 production is presented in bins of the transverse momentum and the energy of the D0 meson