14 research outputs found
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 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 that
in turn affect the extraction of the isosinglet coupling and the
strange quark spin component 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
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Erratum to: Hadron transverse momentum distributions in muon deep inelastic scattering at 160Â GeV/c [European Physical Journal C, 73, 2531, (2013), DOI:10.1140/epjc/s10052-013-2531-6]
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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 ăp ă on x , Q , W and z. The z-dependence of ăp ă is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons, ăk ă, 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 â„ B
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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 ăp2T ă on xBj , Q2, W2 and z. The z-dependence of ăp2T ă is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons, ăk2â„ă, as a function of xBj and Q2 in a leading order QCD parton model
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