arXiv subjects

Richard D. Ball

Publications and source records attributed to Richard D. Ball.

97 records · Page 6Linked to original sources

arXiv1996

Measurement of the Polarized Structure Function g_1^p at HERA

We present estimates of possible data on spin-dependent asymmetries in inclusive scattering of high energy polarized electrons by high energy polarized protons at HERA, including statistical errors, and discuss systematic uncertainties. We show that these data would shed light on the small x behaviour of the polarized structure function g_1, and would reduce substantially the uncertainty on the determination of the polarized gluon distribution.

hep-ph↗

arXiv1996

Polarized Partons at Next-to-Leading Order

We discuss the determination of polarized parton distributions from a next-to-leading order analysis of recent experimental data. We extract the first moment of the polarized quark and gluon distribution and assess the corresponding uncertainties, with special regard to those related to scheme dependence.

hep-ph↗

arXiv1996

Double scaling violations

We discuss the theoretical implications of the scaling properties of F_2^p at small x observed in recent HERA experiments. We show that low Q^2 data display double scaling violations which are adequately described by NL ln Q^2 corrections. Scaling violations due to summations of leading and subleading ln 1/x beyond NLO in ln Q^2 are however disfavoured by the data.

hep-ph↗

arXiv1996

Inclusive Measurement of the Strong Coupling at HERA

We describe the measurement of the strong coupling alpha_s from data on inclusive DIS at high energies. We present new results using the 1994 data from H1, and confirm directly the expected running of alpha_s.

hep-ph↗

arXiv1995

Universality and Scaling in Perturbative QCD at Small x

We present a pedagogical review of the universal scaling properties displayed by the structure function F_2 at small x and large Q^2 as measured at HERA. We first describe the derivation of the double asymptotic scaling of F_2 from the leading-order Altarelli-Parisi equations of perturbative QCD. Universal next-to-leading order corrections to scaling are also derived. We explain why the universal scaling behaviour is spoiled when the initial distributions rise too steeply by considering the nonsinglet distribution F_2^p-F_2^n as an explicit example. We then examine the stability of double scaling to the inclusion of higher order singularities, explaining how the perturbative expansion at small x can be reorganized in such a way that each order is given by the sum of a convergent series of contributions which are of arbitrarily high order in the coupling. The wave-like nature of perturbative evolution is then shown to persist throughout almost all the small x region, giving rise asymptotically to double scaling for a wide class of boundary conditions.

hep-ph↗

arXiv1994

Anomalous Evolution of Nonsinglet Structure Functions

We review a formalism that includes the effects of nonperturbative U(1) symmetry breaking on the QCD evolution of nonsinglet structure functions. We show that a strong scale dependence is generated in an intermediate energy range $0.5 \lsim Q^2 \lsim 5$~GeV$^2$ for all values of $x$. We show that this explains naturally the observed violation of the Gottfried sum, and allows a determination of the shape of the nonsinglet structure function, in excellent agreement with experiment. We argue that these effects may affect the determination of $α_s$ from deep--inelastic scattering.

hep-ph↗

arXiv1993

A Dynamical Resolution of the Sigma Term Puzzle

We propose a resolution of the puzzle posed by the discrepancy between the pion-nucleon sigma term inferred from pion-nucleon scattering, and that deduced from baryon mass splittings using the Zweig rule. We show that there is a significant hypercharge-dependent dynamical contribution to baryon masses, not hitherto included in the analysis, which may be estimated using the scale Ward identity, and computed by solution of the Schwinger-Dyson equation for the quark self-energy. We find that the discrepancy is completely resolved without the need for any Zweig rule violation.

hep-ph↗