2,571 research outputs found

    The Charm Quark on the Lattice

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    We formulate lattice fermions in a way that encompasses Wilson fermions as well as the static and non-relativistic approximations. In particular, we treat mqam_qa systematically (mqm_q is the fermion mass) showing how to understand the Wilson action as an effective action for systems with \vek{p}\ll m_q. The results show how to extract matrix elements and the spectrum from simulations with mqa≈1m_qa\approx1, which is relevant for the charm quark.Comment: 4 pages LaTeX using espcrc2.sty and epsf.sty. FERMILAB-CONF-92/329-

    The Isgur-Wise Limit on the Lattice

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    We construct the Isgur-Wise limit of QCD in a form appropriate to lattice gauge theory techniques. The formulation permits a calculation of heavy quark processes even when the momentum transfers are much larger than the inverse lattice spacing. Applications include semi-leptonic heavy quark decay and scattering processes, including the computation of the nonperturbative part of the Isgur-Wise universal function.Comment: Talk given at the 1992 International Lattice Gauge Theory Conference ("Lattice '92"), Amsterdam, 4 pages, in postscrip

    Color-Coulomb Force Calculated from Lattice Coulomb Hamiltonian

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    The static color-Coulomb potential is calculated as the solution of a non-linear integral equation. This equation has been derived recently as a self-consistency condition which arises in the Coulomb Hamiltonian formulation of lattice gauge theory when the restriction to the interior of the Gribov horizon is implemented. The potential obtained is in qualitative agreement with expectations, being Coulombic with logarithmic corrections at short range and confining at long range. The values obtained for the string tension and ΛMS‟\Lambda_{\overline{MS}} are in semi-quantitative agreement with lattice Monte Carlo and phenomenological determinations.Comment: 4 pages (including 1 figure); (latex using espcrc2.sty). Talk presented at LATTICE96(poster

    Investigation of Quark-Antiquark Interaction Properties using Leading Particle Measurements in e+e- Annihilation

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    Measurements of heavy quark production in electron-positron collisions are used to analyse the strong interactions between quarks and anti-quarks. A scaling behaviour is observed in distributions of the rapidity change of D*, B*, and B mesons. From these distributions information is obtained on the hadron formation time, effective quark masses, and the potential between quark-antiquark pairs. Predictions for fragmentation functions are presented.Comment: 10 pages, 4 figures, fig.2 references added, revised version accepted by Physics Letters

    Can a light technipion be discovered at the Tevatron if it decays to two gluons?

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    In multiscale and topcolor-assisted models of walking technicolor, light, spin-one technihadrons can exist with masses of a few hundred GeV; they are expected to decay as rho_T -> W pi_T. For technirho masses ~200 GeV and technipion masses ~100 GeV, the process pbar p -> rho_T -> W pi_T has a cross section of about a picobarn at the Tevatron. We demonstrate the detectability of this process with simulations appropriate to Run II conditions, for the challenging case where the technipion decays dominantly into two gluons.Comment: 11 pages, LaTeX, including figure

    Low-Scale Technicolor at the Tevatron and LHC

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    The Tevatron experiments CDF and DO are close to making definitive statements about the technicolor discovery mode rho_T -> W pi_T for M(rho_T) <~ 230 GeV and M(pi_T) <~ 125 GeV. We propose new incisive tests for this mode and searches for others that may be feasible at the Tevatron and certainly are at the LHC. The other searches include two long discussed, namely, omega_T -> gamma pi_T and l+l-, and a new one -- for the I^G J^{PC} = 1^- 1^{++} partner, a_T, of the rho_T. Adopting the argument that the technicolor contribution to S is reduced if M(a_T) is near M(rho_T), we enumerate important a_T decays and estimate production rates at the colliders.Comment: Version to be published in Physics Letters B. Revised to reflect latest CDF search for technirho to W technipi and new studies of the LHC's reach for low-scale technicolo

    Variational calculation of heavy-light meson properties

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    We present a new method for the study of heavy-light mesons in the static approximation of lattice QCD which is optimally effective in isolating ground and excited states. With ``MOST'' (Maximal Operator Smearing Technique), the heavy quark is smeared at all possible positions relative to the light quark, subject to the constraint of cubic symmetry. With correlation functions constructed using this set as a variational basis, eigenstates of the transfer matrix are projected out at very small time separations, where statistical errors are small. We illustrate the utility of the method with preliminary results for the meson decay constant fBstatf_{B}^{\rm stat}, binding energies and wave functions of the lowest states. The method produces dynamically-improved interpolating fields which can be used for matrix element calculations.Comment: 3pages, uuencode-compressed-tar Postscript file. (160 kbytes), preprint number uk/93-0

    Charmonium levels near threshold and the narrow state X(3872) \to \pi^{+}\pi^{-}\jpsi

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    We explore the influence of open-charm channels on charmonium properties, and profile the 1:3D2, 1:3D3 and 2:1P1 charmonium candidates for X(3872). The favored candidates, the 1:3D2 and 1:3D3 levels, both have prominent radiative decays. The 1:3D2 might be visible in the D0Dˉ∗0D^{0}\bar{D}^{*0} channel, while the dominant decay of the 1:3D3 state should be into DDˉD\bar{D}. We propose that additional discrete charmonium levels can be discovered as narrow resonances of charmed and anticharmed mesons.Comment: 8 pages, 6 figures, uses RevTeX and boxedeps; few transcription errors corrected in Tables IV and VI, three entries added in Table V, updated references. Version to appear in Phys. Rev.

    Structural Properties of the Lattice Heavy Quark Effective Theory

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    We discuss two related aspects of the lattice version of the heavy quark effective theory (HQET). They are the effects of heavy quark modes with large momenta, near the boundary of the Brillouin zone, and the renormalization of the lattice HQET. We argue that even though large momentum modes are present, their contributions to heavy-light bound states and perturbative loop integrals are dynamically suppressed and vanish in the continuum limit. We also discuss a new feature of the renormalization of the lattice HQET not present in the continuum theory, namely that the classical velocity is finitely renormalized.Comment: 4 pages; postscript; no figures; Talk at Lattice `94 (Bielefeld

    Strong Dynamics at the Muon Collider: Working Group Report

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    New strong dynamics at the energy scale ~ 1 TeV is an attractive and elegant theoretical ansatz for the origin of electroweak symmetry breaking. We review here the theoretical models for strong dynamics, particularly, technicolor theories and their low energy signatures. We emphasize that the fantastic beam energy resolution (sigma_E/E ~10^{-4}) expected at the first muon collider (sqrt{s} = 100-500 GeV) allows the possibility of resolving some extraordinarily narrow technihadron resonances and, Higgs-like techniscalars produced in the s-channel. Investigating indirect probes for strong dynamics such as search for muon compositeness, we find that the muon colliders provide unparallel reaches. A big muon collider (sqrt{s} =3-4 TeV) would be a remarkable facility to study heavy technicolor particles such as the topcolor Z', to probe the dynamics underlying fermion masses and mixings and to fully explore the strongly interacting electroweak sector.Comment: 19 pages, 10 figures, uses aipproc. Plenary talk at the Fermilab Workshop on Physics at the First Muon Collider and at the Front End of a Muon Collider, November 199
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