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Paul B. Mackenzie

Publications and source records attributed to Paul B. Mackenzie.

26 records · Page 2Linked to original sources
arXiv1996

The Light Quark Masses from Lattice Gauge Theory

We investigate the masses of the light quarks with lattice QCD. We show that most of the large dependence on the lattice spacing, a, observed in previous determinations using Wilson fermions is removed with the use of an O(a) corrected action. In the quenched approximation, we obtain for the strange quark MS bar mass m_s(2 GeV) = 95 (16) MeV, and for the average of the up and down quark masses m_l(2 GeV) = 3.6 (6) MeV. Short distance arguments and existing staggered fermion calculations make it likely that the answers including the effects of quark loops lie 20 % to 40 % below this: m_s(2 GeV) in the range 54-92 MeV, and m_l(2 GeV) in the range 2.1-3.5 MeV. We argue that almost all lattice determinations of the light quark masses are consistent with these values. These low values are outside the range usually given by conventional phenomenology.

hep-ph↗
arXiv1996

Recent Lattice Results on the Light Quark Masses

I discuss old and new determinations of the light quark masses using lattice QCD. Most lattice results using various approximations can be fit together in a simple picture which is consistent with lower values than conventionally supposed: in the quenched approximation for the strange quark mass in the MS bar scheme, m_s(2 GeV) = 95 (16) MeV, and for the average of the u and d quark masses, m_l(2 GeV) = 3.6 (6) MeV. An estimate of the effects of light quark loops yields answers lower still: m_s(2 GeV) in the range 54 - 92 MeV, and m_l(2 GeV) in the range 2.1 - 3.5 MeV.

hep-ph↗
arXiv1996

Massive Fermions in Lattice Gauge Theory

This paper presents a formulation of lattice fermions applicable to all quark masses, large and small. We incorporate interactions from previous light-fermion and heavy-fermion methods, and thus ensure a smooth connection to these limiting cases. The couplings in improved actions are evaluated for arbitrary fermion mass~$m_q$, without expansions around small- or large-mass limits. We treat both the action and external currents. By interpreting on-shell improvement criteria through the lattice theory's Hamiltonian, one finds that cutoff artifacts factorize into the form $b_n(m_qa)[\vek{p}a]^{s_n}$, where $\vek{p}$ is a momentum characteristic of the system under study, $s_n$ is related to the dimension of the $n$th interaction, and $b_n(m_qa)$ is a bounded function, numerically always~$\order(1)$ or less. In heavy-quark systems $\vek{p}$ is typically rather smaller than the fermion mass~$m_q$. Therefore, artifacts of order $(m_qa)^s$ do not arise, even when $m_qa\gsim1$. An important by-product of our analysis is an interpretation of the Wilson and Sheikholeslami-Wohlert actions applied to nonrelativistic fermions.

hep-lat↗
arXiv1993

Status of Lattice QCD

Significant progress has recently been achieved in the lattice gauge theory calculations required for extracting the fundamental parameters of the standard model from experiment. Recent lattice determinations of such quantities as the kaon $B$ parameter, the mass of the $b$ quark, and the strong coupling constant have produced results and uncertainties as good or better than the best conventional determinations. Many other calculations crucial to extracting the fundamental parameters of the standard model from experimental data are undergoing very active development. I review the status of such applications of lattice QCD to standard model phenomenology, and discuss the prospects for the near future.

hep-ph↗
arXiv1993

Progress in QCD Using Lattice Gauge Theory

Review of results from lattice QCD of relevance to standard-model phenomenology, to appear in Annual Review of Nuclear and Particle Science. KEY WORDS: hadron masses, quark mixing (CKM) matrix, weak matrix elements, strong coupling constant.

hep-ph↗
arXiv1992

A New Action for Heavy Lattice Fermions

I describe a unified formalism for lattice fermions, in which the relativistic action of Wilson and the nonrelativistic and static actions appear as special cases. It is valid at all values of $m_q a$, including $m_q a \approx 1$. In the limit $m_q a \ll 1 $, the formulation reduces to the light quark action of Wilson. In the limit $m_q a \gg 1 $, the formulation reduces to the nonrelativistic action of Thacker and Lepage, and to the static action of Eichten.

hep-lat↗
arXiv1992

Heavy Quark Physics

Lattice calculations of heavy quark systems provide very good measures of the lattice spacing, a key element in recent determinations of the strong coupling constant using lattice methods. They also provide excellent testing grounds for lattice methods in general. I review recent phenomenological and technical developments in this field.

hep-lat↗