Triply Differential Positron and Electron Impact Ionization of Argon: Systematic Features and Scaling

Triply differential data are presented for the 200 eV positron and electron impact ionization of argon. Six electron emission energies between 2.6 and 19 eV, and for scattering angles of 2, 3, and 4 degrees cover a momentum transfer range of 0.16 to 0.31 a.u. The binary and recoil intensities are fitted using a double peak structure in both regions, which, for the present kinematic conditions, are unresolved. The fitted peak intensities and angular positions are shown to have systematic dependences as a function of the momentum transfer and kinematic emission angle, respectively, and illustrate projectile charge effects. A comparison with available theories is made where it is seen that the most notable differences include the fact that for the binary lobe, the observed intensity for emission angles around 100° is absent in the theories, and the theoretical predications overestimate the importance of recoil interactions.

Diffraction gratings as small-angle X-ray scattering calibration standards

It is shown that diffraction gratings can be used as accurate momentum-transfer calibration standards in small-angle X-ray scattering experiments. For demonstration purposes, a silicon diffraction grating with a period of 400 nm is used. The data exhibit 50 diffraction peaks evenly distributed in the momentum-transfer rangeq= 0.0–0.8 nm−1, a regime that is not accessible using the traditional silver behenate standard.

DEEP-ELASTIC pp SCATTERING AT LHC FROM LOW-x GLUONS

Deep-elastic pp scattering at c.m. energy 14 TeV at LHC in the momentum transfer range 4 GeV 2 ≲ |t| ≲ 10 GeV 2 is planned to be measured by the TOTEM group. We study this process in a model where the deep-elastic scattering is due to a single hard collision of a valence quark from one proton with a valence quark from the other proton. The hard collision originates from the low-x gluon cloud around one valence quark interacting with that of the other. The low-x gluon cloud can be identified as color glass condensate and has size ≃0.3 F. Our prediction is that pp dσ/dt in the large |t| region decreases smoothly as momentum transfer increases. This is in contrast to the prediction of pp dσ/dt with visible oscillations and smaller cross sections by a large number of other models.

FORM FACTORS FOR B→πlν DECAY IN A MODEL CONSTRAINED BY CHIRAL SYMMETRY AND QUARK MODEL

The form factors for the B→π transition are evaluated in the entire momentum transfer range by using the constraints obtained in the framework combining the heavy quark expansion and chiral symmetry for light quarks and the quark model. In particular, we calculate the valence quark contribution and show that it together with the equal time commutator contribution give to the form factors a pole behavior with the heavy (B-meson in our case) mass as the pole mass. This is in addition to the usual vector meson B*-pole diagram for B→πlν in the above framework. We discuss the predictions in our model, which provide an estimate of |Vub|2.