Comparison of 20 exclusive reactions at large t

The differential cross sections for the γ n → π − p and the γp → π + n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50 • to 110 • . The π − and π + photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing π + data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [dσ/dt(γ n → π − p)/dσ/dt(γp → π + n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.

Section: Theoretical and Experimental Backgroundsupporting

confidence: 66%

Section: Theoretical and Experimental Backgroundsupporting

confidence: 58%

See 1 more Smart Citation

Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV

Zhu¹,

Arrington²,

Averett³

et al. 2005

“…In such models, however, the power law of the energy dependence is rather an accidental result. This situation can not explain the "persistent" consistency of the constituent scaling law observed for many hard exclusive reactions including hadronic [8] and photoproduction [9] reactions, involving proton, deuteron and even 3 He targets at |t|, |u| > M 2 i kinematics (see e.g. Refs.…”

Section: Introductionmentioning

confidence: 96%

Scaling and resonances in elementaryK+Λphotoproduction

Schumacher

Sargsian

2011

Recent cross section data for the reaction γ + p → K + + Λ are examined for evidence of scaling in both the low-t Regge domain and in the high √ s and −t domain where constituent counting may apply. It is shown that the reaction does scale in both regimes. At large center of mass angles, s −7 scaling appears to hold at essentially all −t, but with angle-dependent oscillations. The scaled data show particularly strong evidence for s-channel resonances for −t below 2 GeV 2 and for W below about 2.3 GeV. The dominant contributions are consistent with an N * S11 resonance at 1690 MeV,

“…Our further calculations are based on the experimental observation [41] that the quarkinterchange [42] represents the dominant mechanism of hard exclusive scattering of baryons that carry valence quarks with common flavor. The quark-interchange mechanism however will not allow us to calculate the absolute cross sections.…”

Section: Estimates Of the Relative Strength Of The ∆∆ Breakup Re-amentioning

confidence: 99%

Hard breakup of the deuteron into twoΔisobars

Granados

Sargsian

2011

We study high energy photodisintegration of the deuteron into two ∆-isobars at large center of mass angles within the QCD hard rescattering model (HRM). According to the HRM, the process develops in three main steps: the photon knocks a quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons which have large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of pn → ∆∆ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. Calculations show that the angular distribution and the strength of the photodisintegration is mainly determined by the properties of the pn → ∆∆ scattering. We predict that the cross section of the deuteron breakup to ∆ ++ ∆ − is 4-5 times larger than that of the breakup to the ∆ + ∆ 0 channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard ∆-isobars are the result of the disintegration of the preexisting ∆∆ components of the deuteron wave function. In this case, one expects the angular distributions and cross sections of the breakup in both ∆ ++ ∆ − and ∆ + ∆ 0 channels to be similar.