59 research outputs found
Chiral-Odd Generalized Parton Distributions, Transversity and Double Transverse-Spin Asymmetry in Drell-Yan Dilepton Production
Within the framework of light-cone quantization we derive the overlap
representation of generalized parton distributions for transversely polarized
quarks using the Fock-state decomposition in the transverse-spin basis. We
apply this formalism to the case of light-cone wave functions in a constituent
quark model giving numerical results for the four chiral-odd generalized parton
distributions in a region where they describe the emission and reabsorption of
a quark by the nucleon. With the transversity distribution obtained in the
forward limit of the generalized distribution, we provide some predictions for
the double transverse-spin asymmetry in Drell-Yan dilepton production in the
kinematics of the PAX experiment.Comment: 8 pages, 4 figures. To appear in the Proceedings of the "XI
Conference on Problems in Theoretical Nuclear Physics", Cortona, Italy, 11-14
October 200
Chiral-odd generalized parton distributions in constituent quark models
We derive the overlap representation of chiral-odd generalized parton
distributions using the Fock-state decomposition in the transverse-spin basis.
This formalism is applied to the case of light-cone wave functions in a
constituent quark model. Numerical results for the four chiral-odd generalized
parton distributions at the hadronic scale are shown in different kinematics.
In the forward limit we derive the transversity distribution, the tensor charge
and the angular momentum sum rule for quarks with transverse polarization in an
unpolarized nucleon.Comment: 23 pages, 7 figures; one reference added and one formula corrected;
conclusions and discussions unchange
Chiral-Odd Generalized Parton Distributions and Transversity in Light-Front Constituent Quark Models
We present the general framework to calculate chiral-odd generalized parton
distributions in the overlap representation using the Fock-state decomposition
in the transverse spin basis. In the forward limit we derive the transversity
distribution, the tensor charge and the angular momentum sum rule for quarks
with transverse polarization in an unpolarized nucleon. Numerical results are
obtained by applying the formalism to the case of light-cone wavefunctions of
constituent quark models.Comment: 8 pages, 3 figures. Invited talk at the "Advanced Studies Institute
on SYMMETRIES AND SPIN" (SPIN-Praha-2006), 19-26 July, 2006, Prague. To be
pubblished in Czechoslovak Journal of Physics. Some references adde
Drell-Yan processes, transversity and light-cone wavefunctions
The unpolarized, helicity and transversity distributions of quarks in the proton are calculated in the overlap representation of light-cone wavefunctions truncated to the lowest order Fock-space components with three valence quarks. The three distributions at the hadronic scale satisfy an interesting relation consistent with the Soffer inequality. Results are derived in a relativistic quark model including radiative corrections up to the next-to-leading order. Predictions for the double transverse-spin asymmetry in Drell-Yan dilepton production initiated by proton-antiproton collisions are presented. Asymmetries of about 20-30% are found in the kinematic conditions of the PAX experiment
New ways to access the transverse spin content of the nucleon
We first describe a new way to access the chiral odd transversity parton
distribution in the proton through the photoproduction of lepton pairs. The
basic ingredient is the interference of the usual Bethe-Heitler or Drell-Yan
amplitudes with the amplitude of a process, where the photon couples to quarks
through its chiral-odd distribution amplitude, which is normalized to the
magnetic susceptibility of the QCD vacuum. We also show how the chiral-odd
transversity generalized parton distributions (GPDs) of the nucleon can be
accessed experimentally through the exclusive electro - or photoproduction
process of a meson pair with a large invariant mass and when the final nucleon
has a small transverse momentum. We calculate perturbatively the scattering
amplitude at leading order, both in the high energy domain which may be
accessed in electron-ion colliders and in the medium energy range. Estimated
rates are encouraging.Comment: 6 pages, Proceedings of Spin 2010, 19th International Spin Physics
Symposium September 27 - October 2, 2010, J\"ulich, German
Chiral-odd generalized parton distributions, transversity decomposition of angular momentum, and tensor charges of the nucleon
The forward limit of the chiral-odd generalized parton distributions (GPDs)
and their lower moments are investigated within the framework of the chiral
quark soliton model (CQSM), with particular emphasis upon the transversity
decomposition of nucleon angular momentum proposed by Burkardt. A strong
correlation between quark spin and orbital angular momentum inside the nucleon
is manifest itself in the derived second moment sum rule within the CQSM,
thereby providing with an additional support to the qualitative connection
between chiral-odd GPDs and the Boer-Mulders effects. We further confirm
isoscalar dominance of the corresponding first moment sum rule, which indicates
that the Boer-Mulders functions for the - and -quarks have roughly equal
magnitude with the same sign. Also made are some comments on the recent
empirical extraction of the tensor charges of the nucleon by Anselmino et al.
We demonstrate that a comparison of their result with any theoretical
predictions must be done with great care, in consideration of fairly strong
scale dependence of tensor charges, especially at lower renormalization scale.Comment: version to appear in Phys. Rev.
Nucleon to Pion Transition Distribution Amplitudes in a Light-Cone Quark Model
We present a general representation for the nucleon distribution amplitudes
and for the nucleon to pion transition distribution amplitudes in terms of
light-cone wave functions. We apply our formalism to a light-cone constituent
quark model giving some numerical results for both the classes of observables.Comment: 8 pages, 2 figures and a table. Invited talk at `Transversity 2008',
Ferrara, Italy, 28-31 May 200
Parton content of the nucleon from distribution amplitudes and transition distribution amplitudes
The nucleon distribution amplitudes and the nucleon-to-pion transition
distribution amplitudes are investigated at leading twist within the frame of a
light-cone quark model. The distribution amplitudes probe the three-quark
component of the nucleon light-cone wave function, while higher order
components in the Fock-space expansion of the nucleon state are essential to
describe the nucleon-to-pion transition distribution amplitudes. Adopting a
meson-cloud model of the nucleon the nucleon-to-pion transition distribution
amplitudes are calculated for the first time.Comment: comments and references added; version to appear in Phys. Rev.
Effects of alirocumab on types of myocardial infarction: insights from the ODYSSEY OUTCOMES trial
Aims The third Universal Definition of Myocardial Infarction (MI) Task Force classified MIs into five types: Type 1, spontaneous; Type 2, related to oxygen supply/demand imbalance; Type 3, fatal without ascertainment of cardiac biomarkers; Type 4, related to percutaneous coronary intervention; and Type 5, related to coronary artery bypass surgery. Low-density lipoprotein cholesterol (LDL-C) reduction with statins and proprotein convertase subtilisin–kexin Type 9 (PCSK9) inhibitors reduces risk of MI, but less is known about effects on types of MI. ODYSSEY OUTCOMES compared the PCSK9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome (ACS) and elevated LDL-C (≥1.8 mmol/L) despite intensive statin therapy. In a pre-specified analysis, we assessed the effects of alirocumab on types of MI. Methods and results Median follow-up was 2.8 years. Myocardial infarction types were prospectively adjudicated and classified. Of 1860 total MIs, 1223 (65.8%) were adjudicated as Type 1, 386 (20.8%) as Type 2, and 244 (13.1%) as Type 4. Few events were Type 3 (n = 2) or Type 5 (n = 5). Alirocumab reduced first MIs [hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.77–0.95; P = 0.003], with reductions in both Type 1 (HR 0.87, 95% CI 0.77–0.99; P = 0.032) and Type 2 (0.77, 0.61–0.97; P = 0.025), but not Type 4 MI. Conclusion After ACS, alirocumab added to intensive statin therapy favourably impacted on Type 1 and 2 MIs. The data indicate for the first time that a lipid-lowering therapy can attenuate the risk of Type 2 MI. Low-density lipoprotein cholesterol reduction below levels achievable with statins is an effective preventive strategy for both MI types.For complete list of authors see http://dx.doi.org/10.1093/eurheartj/ehz299</p
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