Eikonalized mini-jet cross-sections in γγ\gamma \gamma collisions

In this note we assess the validity and uncertainties in the predictions of the eikonalised mini-jet model for $\sigma^{inel}_{\gamma \gamma}$. We are able to find a choice of parameters where the predictions are compatible with the current data. Even for this restricted range of parameters the predictions at the high c.m. energies, which can be reached at the TeV energy $e^+e^-$ colliders, differ by about $\pm 25\%$. LEP 2 data can help pinpoint these parameters and hence reduce the uncertainties in the predictions.Comment: 5 pages, latex, requires epsfig.sty, a4wide.sty, full ps file available at http://hpteor.lnf.infn.it/pancheri/lc2000.p

Total Cross-sections

We examine the energy dependence of total cross-sections for photon processes and discuss the QCD contribution to the rising behaviourComment: 5 pages, LaTeX, 2 figures, talk presented by G. Pancheri at Photon - 2001, The International Conference on Structure and Interactions of Photons, Ascona, Sept. 2-7,2001. To appear in the proceeding

Total Photonic and Hadronic Cross-sections

We discuss total cross-sections within the context of the QCD calculable mini-jet model, highlighting its successes and failures. In particular we show its description of $\gamma \gamma \to hadrons$ and compare it with OPAL and L3 data. We extrapolate this result to $\gamma p$ total cross-sections and propose a phenomenological ans\"atz for virtual photon cross-sections. We point out that the good agreement with data obtained with the Eikonal Minijet Model should not hide the many uncertainties buried in the impact parameter distribution. A model obtained from Soft Gluon Summation is briefly discussed and its application to hadronic cross-sections is shown.Comment: 10 pages, 5 figures, LaTeX, uses aipproc.sty. To appear in the proceedings of Photon 2000, Ambelside, U.K., Aug 2000. The title, the number of pages and the number of figures in the announcement were corrected to correspond to the submitted pape

QCD and Total Cross-sections

We discuss models for total cross-sections, show their predictions for photon-photon collisions and compare them with the recent LEP measurements. We show that the extrapolations to high center of mass energies within various models differ by large factors at high energies and discuss the precision required from future measurements at the proposed Linear Collider which would allow to distinguish between them.Comment: 7 pages, 4 figures, laTeX, requires sprocl.sty, added at the end. To appear in the Proceedings of XXIX International Symposium on Mutliparticle Dynamics, Brwon University, U.S.A., June 9

Photon-Photon total inelastic cross-section

We discuss predictions for the total inelastic gamma-gamma cross-section and their model dependence on the input parameters. We compare results from a simple extension of the Regge Pomeron exchange model as well as predictions from the eikonalized mini-jet model with recent LEP data.Comment: 7 pages, LateX, 2 eps figures. Talk presented at Photon'97, Egmond aan Zee, May 199

Predictions for the γγ\gamma \gamma total cross-section in the TeV region: an update

In this talk we present an update of model predictions for the $\gamma \gamma$ total cross-section in the TeV region. The update includes preliminary results for $\gamma \gamma$ cross-sections using the Bloch-Nordsieck model for the overlap function of the partons in the transverse space, use of the CJLK parametrisation of the photonic parton densities that has recently become available and extension to the higher $\gamma \gamma$ energies relevant to the planned CLIC collider.Comment: Talk presented by A. De Roeck at the International Linear Collider Workshop, Jeju Island, Aug. 26-30,2002. To appear in the proceedings. 10 pages, LaTeX file, requires A4.sty, four figure

Exploring CP Violation in the MSSM

We explore the prospects for observing CP violation in the minimal supersymmetric extension of the Standard Model (MSSM) with six CP-violating parameters, three gaugino mass phases and three phases in trilinear soft supersymmetry-breaking parameters, using the CPsuperH code combined with a geometric approach to maximize CP-violating observables subject to the experimental upper bounds on electric dipole moments. We also implement CP-conserving constraints from Higgs physics, flavour physics and the upper limits on the cosmological dark matter density and spin-independent scattering. We study possible values of observables within the constrained MSSM (CMSSM), the non-universal Higgs model (NUHM), the CPX scenario and a variant of the phenomenological MSSM (pMSSM). We find values of the CP-violating asymmetry A_CP in b -> s gamma decay that may be as large as 3%, so future measurements of A_CP may provide independent information about CP violation in the MSSM. We find that CP-violating MSSM contributions to the B_s meson mass mixing term Delta M_Bs are in general below the present upper limit, which is dominated by theoretical uncertainties. If these could be reduced, Delta M_Bs could also provide an interesting and complementary constraint on the six CP-violating MSSM phases, enabling them all to be determined experimentally, in principle. We also find that CP violation in the h_{2,3} tau+ tau- and h_{2,3} tbar t couplings can be quite large, and so may offer interesting prospects for future pp, e+ e-, mu+ mu- and gamma gamma colliders.Comment: 36 pages, 32 figure

Total Cross-sections and Bloch-Nordsieck Gluon Resummation

The physics underlying the fall and eventual rise in various total cross-sections at high energies has been investigated over a decade using a model based on the Bloch-Nordsieck resummation in QCD. Here a brief review of our latest results is presented and comparison made with experimental data on $pp$, $\gamma proton$ and $\gamma \gamma$ total cross-sections.Comment: Presented by G. Pancheri at ISMD04, Sonoma State University. Under publication in Acta Physica Polonica. LaTeX format, 10 *.eps files, 7 page

Total Cross Sections

A unified approach to total cross-sections, based on the QCD contribution to the rise with energy, is presented for the processes $pp$, $p{\bar p}$, $\gamma p, \gamma \gamma, e^+e^- \to hadrons$. For proton processes, a discussion of the role played by soft gluon summation in taming the fast rise due to mini-jets is presented. For photon-photon processes, a comparison with other models indicates the need for precision measurements in both the low and high energy region, likely only with measurements at future Linear Colliders.Comment: 15 pages, 9 figures, LaTeX, uses hsproc.sty and art10.sty. Talk given by G. Pancheri at 'International Hadron Structure-2000', October 1-6, Staralesn