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P. N. Burrows

Publications and source records attributed to P. N. Burrows.

54 records · Page 3Linked to original sources
arXiv1999

Searches for anomalous effects in the b bbar g coupling

The unique SLD CCD vertex detector combined with the highly-polarised electron beam allow us to search for an anomalous chromomagnetic coupling of the b-quark, as well as P-odd, T_N-odd and CP-odd processes at the b bbar g vertex.

hep-ex↗
arXiv1999

Measurement of the running b-quark mass using $e^+e^- \to b\bar{b}g$ events

We have studied the determination of the running b-quark mass, $m_b(M_Z)$, using $Z^0$ decays into 3 or more hadronic jets. We calculated the ratio of $\geq3$-jet fractions in $e^+e^-\to b\bar{b}$ vs. $e^+e^-\to q_l\bar{q_l}$ ($q_l$ = u or d or s) events at next-to-leading order in perturbative QCD using six different infra-red- and collinear-safe jet-finding algorithms. We compared with corresponding measurements from the SLD Collaboration and found a significant algorithm-dependence of the fitted $m_b(M_Z)$ value. Our best estimate, taking correlations into account, is $m_b(M_Z) = 2.56 \pm 0.27 (stat.) ^{+0.28}_{-0.38} (syst.) ^{+0.49}_{-1.48} (theor.) GeV/c^2$.

hep-ph↗
arXiv1999

A CCD vertex deetctor for a high-energy linear e+e- collider

I present a summary of the experience with CCD-based vertex detectors at the SLD experiment at SLAC, and discuss their advantages for use at a future high-energy e+e- collider. The extensive R+D programme to improve further the vertexing capabilities of CCD detectors is also outlined.

hep-ex↗
arXiv1998

Heavy quark mass effects and improved tests of the flavour independence of strong interactions

A review is given of latest results on tests of the flavour independence of strong interactions. Heavy quark mass effects are evident in the data and are now taken into account at next-to-leading order in QCD perturbation theory. The strong-coupling ratios alpha_s^b/alpha_s^uds and alpha_s^c/alpha_s^uds are found to be consistent with unity. Determinations of the b-quark mass m_b(M_Z) are discussed.

hep-ex↗
arXiv1997

Event Orientation in e+e- Annihilation

We review the orientation of e+e- \to q\bar q g events in terms of the polar and azimuthal angles of the event plane w.r.t. the electron beam direction. The asymmetry of the azimuthal-angle distribution is, like the left-right forward-backward polar-angle asymmetry, sensitive to parity-violating effects in three-jet events; these are presently being explored experimentally. We present these observables at O(α_s) in perturbative QCD and discuss their dependence on longitudinal beam polarisation and c.m. energy. A moments analysis in terms of the orientation angles allows a more detailed test of QCD by isolating the independent helicity cross-sections.

hep-ph↗
arXiv1997

Results on alpha_s and QCD from (and Above) the Z0

Measurements of alpha_s from e+e- annihilation experiments are reviewed and compared with measurements from other processes. Highlights are presented of recent QCD studies in e+e- annihilation at the Z0 resonance.

hep-ex↗
arXiv1997

Precise Tests of QCD in e+e- Annihilation

A pedagogical review is given of precise tests of QCD in electron-positron annihilation. Emphasis is placed on measurements that have served to establish QCD as the correct theory of strong interactions, as well as measurements of the coupling parameter alpha-s. An outlook is given for future important tests at a high energy e+e- collider.

hep-ex↗
arXiv1997

Three-Jet Event Orientation in e+e- Annihilation: New Tests of the Standard Model

We discuss the orientation of e+e- -> q qbar g events in terms of the polar and azimuthal angles of the event plane w.r.t. the electron beam direction. We define an asymmetry of the azimuthal-angle distribution, which, along with the left-right forward-backward polar-angle asymmetry, is sensitive to parity-violating effects in three-jet events; these have yet to be explored experimentally. We have evaluated these observables at O(alpha_s) in perturbative QCD and present their dependence on longitudinal beam polarisation and c.m. energy. We also define a moments analysis in terms of the orientation angles that allows a new and more detailed test of QCD by isolating the six independent helicity cross-sections.

hep-ph↗
arXiv1996

Prospects for the Precision Measurement of Alpha_S

The prospects for the measurement of the strong coupling constant alpha_msbar(M_Z) to a relative uncertainty of 1% are discussed. Particular emphasis is placed on the implications relating to future High Energy Physics facilities.

hep-ex↗
arXiv1996

Review of alpha-s Measurements

Determinations of alpha_s are reviewed. Current results are limited to a precision of around 3-20%, largely by theoretical uncertainties. All measurements are consistent with a `world average' value of 0.118 +- 0.005 and there is no evodence of any discrepancy between `low-Q^2' and `high-Q^2' results.

hep-ex↗
arXiv1996

Determination of alpha_s(M_Z^2) from hadronic event shape observables in e+e- annihilation

The determination of alpha_s(M_Z^2) using O(alpha_s^2) calculations of hadronic event observables in e+e- annihilation is reviewed. The large scatter among alpha_s(M_Z^2) values determined from different observables may be interpreted as arising from the effect of uncalculated higher-order contributions. The application of `optimised' perturbation theory and Pade approximants in an attempt to reduce this effect is discussed.

hep-ex↗
arXiv1996

Application of Pade Approximants to Determination of alpha_s(M_Z^2) from Hadronic Event Shape Observables in e+e- Annihilation

We have applied Pade approximants to perturbative QCD calculations of event shape observables in e+e- --> hadrons. We used the exact O(alpha_s^2) prediction and the [0/1] Pade approximant to estimate the O(alpha_s^3) term for 15 observables, and in each case determined alpha_s(M_Z^2) from comparison with hadronic Z^0 decay data from the SLD experiment. We found the scatter among the alpha_s(M_Z^2) values to be significantly reduced compared with the standard O(alpha_s^2) determination, implying that the Pade method provides at least a partial approximation of higher-order perturbative contributions to event shape observables.

hep-ph↗
arXiv1996

Application of 'Optimised' Perturbation Theory to Determination of alpha_s(M_Z^2) from Hadronic Event Shape Observables in e+e- Annihilation

We have applied so-called `optimised' perturbation theory to resolve the renormalisation-scale (mu) ambiguity of exact O(alpha_s^2) QCD calculations of event shape observables in e+e- --> hadrons. We fitted the optimised predictions for 15 observables to hadronic Z0 decay data from the SLD experiment to determine alpha_s(M_Z^2). Comparing with results using the physical scale mu = M_Z we found no reduction in the scatter among alpha_s(M_Z^2) values from the 15 observables, implying that the O(alpha_s^2) predictions with optimised scales are numerically no closer to the exact all-orders results than those with the physical scale.

hep-ph↗