F.J. Ynduráin

Computation of the relation between the quark masses in lattice gauge theories and on the continuum

Abstract We compute the relation between the quark masses on the lattice and on the continuum for a genetic fermion lattice action.

How to look for squarks with the p̄p collider

Abstract We consider Drell-Yan-like production of squarks q from pp, starting with a valence quark and gluino from the sea. The signal would be highly energetic jet, E jet ∼ 1 2 m q , and the same amount of missing energy back to back with it. If m( gluino ) ⪅ 16 GeV , m q ∼ 60–160 GeV . The amount of such signals would be some 14 to 1 times that of the signal for p p → ( W → e v ) + all .

Disappearance of matter due to causality and probability violations in theories with extra timelike dimensions

We prove that, if there exist extra, compact timelike dimensions characterized by the length L, then ensuing causality violations cause quarks (and protons) to disappear into nothingness with a lifetime τ ∼(G12NL)3×1026 yr, with GN Newtons constant, in flat contradiction with experiment if L<∼GN12/10.

Heavy quarkonium systems and nonperturbative field correlators

Abstract Bound states of heavy quarks are considered. Using the path integral formalism we are able to rederive, in a gauge invariant way, the Leutwyler-Voloshin short distance analysis as well as a long distance linear potential. At all distances we describe the states in terms of nonperturbative field correlators, and we include radiative corrections at short and intermediate distances. For intermediate distance states (particularly b b ) with n = 2 our results improve, qualitatively and quantitatively, standard analyses, due mostly to being able to take into account the finiteness of the correlation time.Bound states of heavy quarks are considered. Using the path integral formalism we are able to rederive, in a gauge invariant way, the Leutwyler-Voloshin short distance analysis as well as a long distance linear potential. At all distances we describe the states in terms of nonperturbative field correlators, and we include radiative corrections at short and intermediate distances. For intermediate distance states (particularly

Squark production and signals at the p̄p collider

b\bar {b}

Theory of small x deep inelastic scattering: NLO evaluations, and low Q2 analysis

with

Calculation of electroproduction to NNLO and precision determination of αs

n=2

Pure QCD bounds and estimates for light quark masses

) our results improve, qualitatively and quantitatively, standard analyses, thanks mostly to being able to take into account the finiteness of the correlation time.

Limits on the mass of the gluon

Abstract We consider the signals due to Drell-Yan production of squarks in pp collisions, from a valence quark and a gluino from the sea. We find (i) a bump on the squark mass in two and multijet events; (ii) a certain number of events with jet (quark) and missing p t (photino); (iii) events with one jet (quark), electron/muon and missing p t (photino and neutrino).

The scalar radius of the pion

We calculate structure functions at small x both under the assumption of a hard singularity (essentially, a power behaviour χ−λ, A positive, for x → 0) and that of a soft-pomeron dominated behaviour, also called double scaling limit, for the singlet component. A full next to leading order (NLO) analysis is carried out for the functions F2, FGlue and the longitudinal one FL in ep scattering, and for χF3 in neutrino scattering. The results of the calculations are compared with experimental data, particularly the recent ones from HERA, in the range x ⩽ 0.032, 10 GeV2 Q2 ⩽ 1500 GeV2. We get reasonable fits, with a chi-squared per degree of freedom around two units, with only three-four parameters in both cases. However, none of the assumptions is by itself able to give a fully satisfactory description of the data. The results improve substantially when combining a soft and a hard component; in this case it is even possible to extend the analysis, phenomenologically, to small values of Q2, 0.31 GeV2 ⩽ Q2 ⩽ 8.5 GeV2, and in the x range 6 × 10−6 ⪅ x ⪅ 0.04, with the same hard plus soft pomeron hypothesis by assuming a saturating expression for the strong coupling, αs (Q2) = 4π / β0 log[ (Q2 + Γeff2) / Γeff2 1. The formulation for low Q2 implies self-consistent values for the parameters in the exponents of x both for singlet and non-singlet components. One has to have, for the Regge intercepts, αϱ(0) = 0.48 and αϱ(0) = 1.470 [λ = 0.470], in uncanny agreement with other determinations of these parameters, and in particular the results of the large Q2 fits. The fit to data is so good that we may look (at large Q2) for signals of a “triple pomeron” vertex, for which some evidence is found. The quality of the calculations of F2, and of the predictions for FGlue, FL is only marred by the very large size of the NLO corrections for the singlet part of F2. This, in particular, forbids a truly reliable determination of the QCD parameter, A.