ترغب بنشر مسار تعليمي؟ اضغط هنا

An attempt to understand exclusive pi+ electroproduction

159   0   0.0 ( 0 )
 نشر من قبل Peter Kroll
 تاريخ النشر 2009
  مجال البحث
والبحث باللغة English
 تأليف S.V. Goloskokov




اسأل ChatGPT حول البحث

Hard exclusive pi+ electroproduction is investigated within the handbag approach. The prominent role of the pion-pole contribution is demonstrated. It is also shown that the experimental data require a twist-3 effect which ensues from the helicity-flip generalized parton distribution H_T and the twist-3 pion wave function. The results calculated from this handbag approach are compared in detail with the experimental data on cross sections and spin asymmetries measured with a polarized target. It is also commented on consequences of this approach for exclusive pi^0 and vector-meson electroproduction.



قيم البحث

اقرأ أيضاً

The process of exclusive electroproduction of vector quarkonium (EEQ), $e pto epV$, is per se an interesting topic in studies of quarkonium production mechanism, QCD description of diffractive interaction and nucleon structure. We investigate this pr ocess in the framework of nonrelativistic QCD and QCD collinear factorization at the next-to-leading order QCD accuracy. The perturbative convergence behavior is discussed in a large range of photon virtuality $Q^2$. The $J/psi$ large-$Q^2$ electroproduction data at HERA can be well explained, and the $Upsilon$ differential production rate is predicted. The uncertainties in theoretical predictions with radiative corrections are greatly reduced. Notice the EEQ process is extremely sensitive to the gluon distribution in nucleon, the generalized parton distribution, our results will constraint the gluon density with high precision while confronting to the future experimental data. For the sake of comparing convenience, the analytic expressions are provided.
156 - P. Kroll 2009
In this talk various spin effects in hard exclusive electroproduction of mesons are briefly reviewed and the data discussed in the light of recent theoretical calculations within the frame work of the handbag approach. For electroproduction of positi vely charged pions it is shown that there is a strong contribution from photon-pion transitions which can be modeled by the transversity GPD H_T accompanied by the twist-3 pion wave function.
156 - S. Basnet , G.M. Huber , W.B. Li 2019
Background: Measurements of exclusive meson production are a useful tool in the study of hadronic structure. In particular, one can discern the relevant degrees of freedom at different distance scales through these studies. Purpose: To study the tran sition between non-perturbative and perturbative Quantum Chromodyanmics as the square of four momentum transfer to the struck proton, -t, is increased. Method: Cross sections for the $^1$H(e,e$pi^+$)n reaction were measured over the -t range of 0.272 to 2.127 GeV$^2$ with limited azimuthal coverage at fixed beam energy of 4.709 GeV, Q$^2$ of 2.4 GeV$^2$ and W of 2.0 GeV at the Thomas Jefferson National Accelerator Facility (JLab) Hall C. Results: The -t dependence of the measured $pi^+$ electroproduction cross section generally agrees with prior data from JLab Halls B and C. The data are consistent with a Regge amplitude based theoretical model, but show poor agreement with a Generalized Parton Distribution (GPD) based model. Conclusion: The agreement of cross sections with prior data implies small contribution from the interference terms, and the confirmation of the change in t-slopes between the low and high -t regions previously observed in photoproduction indicates the changing nature of the electroproduction reaction in our kinematic regime.
Exclusive $pi^0$ electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in $Q^2$, $x_B$, $t$, and $phi_pi$, in the $Q^2$ range from 1.0 to 4.6 GeV$^2$, $-t$ up to 2 GeV$^2$, and $x_B$ from 0.1 to 0.58. Structure functions $sigma_T +epsilon sigma_L, sigma_{TT}$ and $sigma_{LT}$ were extracted as functions of $t$ for each of 17 combinations of $Q^2$ and $x_B$. The data were compared directly with two handbag-based calculations including both longitudinal and transversity GPDs. Inclusion of only longitudinal GPDs very strongly underestimates $sigma_T +epsilon sigma_L$ and fails to account for $sigma_{TT}$ and $sigma_{LT}$, while inclusion of transversity GPDs brings the calculations into substantially better agreement with the data. There is very strong sensitivity to the relative contributions of nucleon helicity flip and helicity non-flip processes. The results confirm that exclusive $pi^0$ electroproduction offers direct experimental access to the transversity GPDs.
We compute the exclusive electroproduction, $gamma^* p rightarrow V p$, of heavy quarkonia $V$ to NLO in the collinear factorisation scheme, which has been formally proven for this process. The inclusion of an off-shell virtuality $Q^2$ carried by th e photon extends the photoproduction phase space of the exclusive heavy quarkonia observable to electroproduction kinematics. This process is relevant for diffractive scattering at HERA and the upcoming EIC, as well as at the proposed LHeC and FCC.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا