Search

Combining recent perturbative analyses on the static QCD potential and the quark pole mass, we find that, for the heavy quarkonium states $c\bar{c}$, $b\bar{b}$ and $t\bar{t}$, (1) ultra-soft (US) corrections in the binding energies are small, and (2) there is a stronger cancellation of IR contributions than what has been predicted by renormalon dominance hypothesis. By contrast, for a hypothetical heavy quarkonium system with a small number of active quark flavors ($n_l\approx 0$), we observe evidence that renormalon dominance holds accurately and that non-negligible contributions from US corrections exist. In addition, we examine contributions of renormalons at $u=- 1$. As an important consequence, we improve on a previous prediction for possible achievable accuracy of top quark $\overline{\rm MS}$--mass measurement at a future linear collider and estimate that in principle 20--30~MeV accuracy is reachable., Comment: 17 pages, 7 figures, 3 tables; Revisions in ver.2: We added (i) a more conservative error estimate of m_t determination, (ii) discussion on u=+1 and u=-1 renormalons, (iii) interpretation of PS-scheme

This lecture note presents a self-contained introduction to the theory of a heavy quark-antiquark ($Q\bar{Q}$) system in terms of perturbative QCD. The lecture is intended for non-experts, such as graduate course students. The heavy $Q\bar{Q}$ system serves as an ideal laboratory for testing various aspects of QCD: We can examine the nature of renormalons in perturbative series; an effective field theory Potential-NRQCD is constructed, whose derivation from full QCD can be traced stepwise; we see absorption of renormalons by non-perturbative matrix elements in OPE clearly; a systematic short-distance expansion of UV contributions can be performed, which predicts a "Coulomb+linear" potential in perturbative QCD; we can test these theoretical formulations by comparison to lattice computations, where we observe a significant overlap with perturbative regime; finally we can test our microscopic understanding by comparing to experimental data for the bottomonium states. These subjects are covered in a concise and elementary manner. Overall, we provide a microscopic description of the main dynamics of a heavy $Q\bar{Q}$ system, as an example for which theoretical framework, practical computations and qualitative understanding have been most advanced., Comment: 65 pages, 58 figures; Based on the lecture courses given at Rikkyo Univ., Kyoto Univ., Karlsruhe Univ. and Nagoya Univ., during 2012--2014

We derive a full formula for the energy level of a heavy quarkonium state identified by the quantum numbers $n$, $\ell$, $s$ and $j$, up to ${\cal O}(\alpha_s^5 m)$ and ${\cal O}(\alpha_s^5 m \log \alpha_s)$ in perturbative QCD. The QCD Bethe logarithm is given in a one-parameter integral form. The rest of the formula is given as a combination of rational numbers, transcendental numbers ($\pi$, $\zeta(3)$, $\zeta(5)$) and finite sums (besides the 3-loop constant $\bar{a}_3$ of the static potential whose full analytic form is still unknown). A derivation of the formula is given., Comment: 45 pages, 1 figure; v2: minor corrections, version to appear in Nucl. Phys. B; v3: typos corrected, in particular eqs. (194) and (227); v4: corrections in eqs.(42),(44),(49); two equations supplemented below eq.(51); no change in the final results

Perturbative QCD has made significant progress over the last few decades. In the first part, we present an introductory overview of perturbative QCD as seen from a modern viewpoint. We explain the relation between purely perturbative predictions and predictions based on Wilsonian effective field theories. We also review progress of modern computational technologies and discuss intersection with frontiers of mathematics. Analyses of singularities in Feynman diagrams play key roles towards developing a unified view. In the second part, we discuss application of perturbative QCD, based on the formulation given in the first part, to heavy quarkonium systems and the interquark force between static color charges. We elucidate impacts on order Lambda_QCD physics in the quark mass and interquark force, which used to be considered inaccessible by perturbative QCD., Comment: 44 pages, 26 figures; lecture given at "QCD Club'' at Univ. Tokyo, June 2014

We compute the energy levels of some of the lower-lying heavy quarkonium states perturbatively up to O(alpha_s^5*m) and O(alpha_s^5*m*log[alpha_s]). Stability of the predictions depends crucially on the unknown 4-loop pole-MSbar mass relation. We discuss the current status of the predictions with respect to the observed bottomonium spectrum., Comment: Short review on non-perturbative contributions included at the end; version to appear in Phys.Lett.; 7 pages, 2 figures

We estimate the presently unknown constant in the 4-loop relation between the quark pole mass and the MSbar mass, by requiring stability of the perturbative prediction for E_tot(r)=2m_pole+V_QCD(r) in the intermediate-distance region. The estimate is fairly sharp due to a severe cancellation between 2m_pole and V_QCD(r). This would provide a test, based on general properties of the gauge theory, for the size of ultra-soft contributions to V_QCD(r)., Comment: 8 pages, 2 figures; Estimate for the nl=0 case added in v2; version to appear in Phys.Lett

Top quark production in the process $e^+e^- \rightarrow t\bar{t}$ at a future linear electron positron collider with polarized beams is a powerful tool to determine the scale of new physics. Studies at the $\ttbar$ threshold will allow for precise determination of the top quark mass in a well defined theoretical framework. At higher energies vector, axial vector and tensorial CP conserving couplings can be separately determined for the photon and the $Z^0$ component in the electro-weak production process. The sensitivity to new physics would be dramatically improved w.r.t. to what expected from LHC for electroweak couplings., Comment: White paper for Snowmass CSS 2013

We propose a new method to measure various physical parameters, using characteristic weight functions. This method requires only lepton energy distribution and ideally it does not depend on the velocity of the parent particle. We demonstrate an application of this method by simulating a reconstruction of the Higgs boson mass in the H-> WW -> lnu lnu decay mode at the LHC. We show that systematic errors are suppressed compared to statistical errors. In the vector boson fusion channel, the statistical accuracy of the mass determination is estimated to be +12% and -14% at an integrated luminosity of 100fb^{-1}, assuming the Higgs boson mass to be 125GeV and root{s}=14TeV., Comment: 31 pages, 15 figures; Version to appear in JHEP

We present algorithms to evaluate two types of multiple sums, which appear in higher-order loop computations. We consider expansions of a generalized hypergeometric-type sums, $\sum_{n_1,...,n_N} [Gamma(a1.n+c1) Gamma(a2.n}+c2) ... Gamma(aM.n+cM)] / [Gamma(b1.n+d1) Gamma(b2.n+d2) ... Gamma(bM.n+dM)] x1^n1...xN^nN $ with $ai.n=\sum_{j=1}^N a_{ij}nj$, etc., in a small parameter epsilon around rational values of ci,di's. Type I sum corresponds to the case where, in the limit epsilon -> 0, the summand reduces to a rational function of nj's times x1^n1...xN^nN; ci,di's can depend on an external integer index. Type II sum is a double sum (N=2), where ci,di's are half-integers or integers as epsilon -> 0 and xi=1; we consider some specific cases where at most six Gamma functions remain in the limit epsilon -> 0. The algorithms enable evaluations of arbitrary expansion coefficients in epsilon in terms of Z-sums and multiple polylogarithms (generalized multiple zeta values). We also present applications of these algorithms. In particular, Type I sums can be used to generate a new class of relations among generalized multiple zeta values. We provide a Mathematica package, in which these algorithms are implemented., Comment: 30 pages, 2 figures; address of Mathematica package in Sec.6; version to appear in J.Math.Phys

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts., Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vairo

We compute the full ${\cal O}(\alpha_s^4)$ and ${\cal O}(\alpha_s^4\log\alpha_s)$ corrections to the potential $V_R(r)$ between the static color sources, where $V_R(r)$ is defined from the Wilson loop in a general representation $R$ of a general gauge group $G$. We find a violation of the Casimir scaling of the potential, for the first time, at ${\cal O}(\alpha_s^4)$. The effect of the Casimir scaling violation is predicted to reduce the tangent of $V_R(r)/C_R$ proportionally to specific color factors dependent on $R$. We study the sizes of the Casimir scaling violation for various $R$'s in the case $G=SU(3)$. We find that they are well within the present bounds from lattice calculations, in the distance region where both perturbative and lattice computations of $V_R(r)$ are valid. We also discuss how to test the Casimir scaling violating effect., Comment: 20 pages, 7 figures, v2: a typo in eq.(13) corrected

We compute the purely gluonic contribution to the static QCD potential at three--loop order. This completes the computation of the static potential at this order., Comment: 4 pages, 2 figures

Recently we have proposed mechanisms to explain origins of the charged lepton spectrum as well as Koide's mass formula, on the basis of U(3)\times O(3) family gauge symmetry. In this note, we review the basic ideas of these mechanisms. Without technical details, and adding some speculations, we give a sketch of the mechanisms, what the important points are and what assumptions are involved. We adopt a known scenario, in which the charged lepton spectrum is determined by the vacuum expectation value of a scalar field that takes values on 3-by-3 matrix. Within this scenario, we propose a mechanism, in which the radiative correction induced by U(3) family gauge interaction cancels the QED radiative correction to Koide's mass formula. We consider SU(9)\times U(1) symmetry broken down to U(3)\times O(3) symmetry. This leads to a potential model which predicts Koide's mass formula and the charged lepton spectrum consistent with the experimental values, by largely avoiding fine tuning of parameters. These are discussed within an effective theory, and we argue for its validity and usefulness., Comment: 17 pages, 12 figures

Koide's mass formula is an empirical relation among the charged lepton masses which holds with a striking precision. We present a model of charged lepton sector within an effective field theory with U(3) \times SU(2) family gauge symmetry, which predicts Koide's formula within the present experimental accuracy. Radiative corrections as well as other corrections to Koide's mass formula have been taken into account. We adopt a known mechanism, through which the charged lepton spectrum is determined by the vacuum expectation value of a 9-component scalar field \Phi. On the basis of this mechanism, we implement the following mechanisms into our model: (1) The radiative correction induced by family gauge interaction cancels the QED radiative correction to Koide's mass formula, assuming a scenario in which the U(3) family gauge symmetry and SU(2)_L weak gauge symmetry are unified at 10^2-10^3 TeV scale; (2) A simple potential of \Phi invariant under U(3) \times SU(2) leads to a realistic charged lepton spectrum, consistent with the experimental values, assuming that Koide's formula is protected; (3) Koide's formula is stabilized by embedding U(3) \times SU(2) symmetry in a larger symmetry group. Formally fine tuning of parameters in the model is circumvented (apart from two exceptions) by appropriately connecting the charged lepton spectrum to the boundary (initial) conditions of the model at the cut-off scale., Comment: 37 pages, 9 figures; Sec.2 added; arguments added in Secs.5 and 7; Version to appear in JHEP

Koide's mass formula is an empirical relation among the charged lepton masses which holds with a striking precision. We propose a mechanism for cancelling the QED correction to Koide's formula. This is discussed in an effective theory with U(3) family gauge symmetry and a scenario in which this symmetry is unified with SU(2)_L symmetry at 10^2-10^3 TeV scale., Comment: 4 pages, no figure; v2: Minor modifications, comment added on anomalies, version to appear in Phys.Lett.B

This Report summarises the activities of the "SM and Higgs" working group for the Workshop "Physics at TeV Colliders", Les Houches, France, 2-20 May, 2005. On the one hand, we performed a variety of experimental and theoretical studies on standard candles (such as W, Z, and ttbar production), treating them either as proper signals of known physics, or as backgrounds to unknown physics; we also addressed issues relevant to those non-perturbative or semi-perturbative ingredients, such as Parton Density Functions and Underlying Events, whose understanding will be crucial for a proper simulation of the actual events taking place in the detectors. On the other hand, several channels for the production of the Higgs, or involving the Higgs, have been considered in some detail. The report is structured into four main parts. The first one deals with Standard Model physics, except the Higgs. A variety of arguments are treated here, from full simulation of processes constituting a background to Higgs production, to studies of uncertainties due to PDFs and to extrapolations of models for underlying events, from small-$x$ issues to electroweak corrections which may play a role in vector boson physics. The second part of the report treats Higgs physics from the point of view of the signal. In the third part, reviews are presented on the current status of multi-leg, next-to-leading order and of next-to-next-to-leading order QCD computations. Finally, the fourth part deals with the use of Monte Carlos for simulation of LHC physics., Comment: 234 pages, 173 figures. Web page of the workshop (with links to the talks): http://lappweb.in2p3.fr/conferences/LesHouches/Houches2005/

We propose a new method for reconstructing an effective spin direction of a semi-leptonically decayed top quark. The method is simple: for instance, it does not require the spin information of the antitop quark in a ttbar event. The reconstructed effective spin is expected to be useful in hadron collider experiments. We demonstrate its usefulness in an analysis of the top decay vertex., Comment: 10 pages, 6 figures; one reference added; version to appear in Phys.Lett.B

We present a quantitative study on sensitivities to the top-decay anomalous couplings, taking into account realistic experimental conditions expected at Tevatron and LHC. A double angular distribution of W and charged lepton in the top decay is analyzed, using ttbar events in the lepton+jets channel. In order to improve sensitivities to the anomalous couplings, we apply two techniques: (1) We use a likelihood fitting method for full kinematical reconstruction of each top event. (2) We develop a new effective spin reconstruction method for leptonically-decayed top quarks; this method does not require spin information of the antitop side. For simplicity, we neglect couplings of right-handed bottom quark as well as CP violating couplings. The 95% C.L. estimated bound on a ratio of anomalous couplings reads -0.81 < f_2/f_1 < -0.70, -0.12

We analyze the static QCD potential in the distance region 0.1 fm < r < 1 fm. We combine most recent lattice computations and perturbative computations of the potential, in the framework of operator-product expansion (OPE). We determine simultaneously the non-perturbative contribution to the potential, delta E_US(r), and the relation between the lattice scale (Sommer scale) and Lambda_MSbar in the quenched approximation. We find that (1) large part of the short-distance linear potential belongs to the perturbative Wilson coefficient, (2) delta E_US(r) =0 is disfavored, and (3) r_0 Lambda_MSbar^(3-loop)=0.574 +- 0.042 . It provides a new method for precise determination of r_0 Lambda_MSbar., Comment: 6 pages, 3 figures, Proceedings for Lattice 2005

We analyze the static QCD potential V_QCD(r) in the distance region 0.1 fm < r < 1 fm using perturbative QCD and OPE as basic theoretical tools. We assemble theoretical developments up to date and perform a solid and accurate analysis. The analysis consists of 3 major steps: (I) We study large-order behavior of the perturbative series of V_QCD(r) analytically. (II) In the frame of OPE, we define two types of renormalization schemes for the leading Wilson coefficient. (III) We compare numerically perturbative predictions of the Wilson coefficient and lattice computations of V_QCD(r). We perform fits to simultaneously determine non-perturbative contribution and the relation between lattice scale and Lambda_MSbar. (Short version), Comment: 60 pages, 28 figures

The leading non-perturbative contribution to the static QCD potential at r << 1/Lambda_QCD is known to be O(r^2) in operator-product expansion. It indicates that a "Coulomb+linear" potential at r <~ 1/Lambda_QCD is included in the perturbative QCD prediction of the potential. It was shown that this is indeed the case, and the "Coulomb+linear" potential has been systematically computed up to next-to-next-to-leading logarithmic order, in terms of the Lambda parameter in the MSbar scheme (Lambda_MSbar). We review the present status of the perturbative prediction for the QCD potential, which takes into account the theoretical breakthrough that took place around 1998., Comment: 10 pages, 6 figures; talk given at Quarks 2004

The static QCD potential is analyzed in operator-product-expansion within potential-NRQCD framework when r << 1/Lambda_{QCD}. We show that the leading short-distance contribution to the potential, defined as a perturbatively computable Wilson coefficient, can be expressed, up to O(r^2), as a ``Coulomb+linear'' potential. It coincides with the ``Coulomb+linear'' potential obtained previously from the renormalon-dominance hypothesis. Non-perturbative contributions are of order r^2 and subleading., Comment: Version to appear in Phys.Lett.B; 4 pages, 2 figures

Recently evidence has been found that the perturbative QCD potential agrees well with phenomenological potentials and lattice computations of the QCD potential. We review the present status of the perturbative QCD potential and theoretical backgrounds. We also report our recent analysis which shows analytically, on the basis of renormalon dominance picture, that the perturbative QCD potential quickly ``converges'' to a Coulomb-plus-linear form. The Coulomb-plus-linear potential can be computed systematically as we include more terms of the perturbative series; up to three-loop running (our current best knowledge), it shows a convergence towards lattice results. e.g. At one-loop running, the linear potential is sigma*r with sigma = (2*pi*C_F/beta0) Lambda_MSbar^2., Comment: Minor changes, References added; 11 pages, 7 figures, Talk given at "Confinement 2003", Riken, Tokyo, July 2003

We extend the formalism based on perturbative QCD that was developed in our previous work, and compute the hyperfine splittings of the bottomonium spectrum as well as the fine and hyperfine splittings of the charmonium spectrum. All the corrections up to O(alpha_s^5 m) are included in the computations. We find agreement (with respect to theoretical uncertainties) with the experimental values whenever available and give predictions for not yet observed splittings., Comment: 9 pages, 3 tables. One short missing paragraph added to ensure conformity with text in PLB

We show analytically that the QCD potential can be expressed, up to an O(Lambda_QCD^3 r^2) uncertainty, as the sum of a ``Coulomb'' potential (with log corrections at short distances) and a linear potential, within an approximation based on perturbative expansion in alpha_S and the renormalon dominance picture. The expansion of V_QCD(r) is truncated at O(alpha_S^N) [N = 6 pi/(beta_0 alpha_S)], where the term becomes minimal according to the estimate by NLO renormalon, and is studied for N >> 1. Analytic expressions for the linear potential are obtained in some cases., Comment: Version to appear in Phys.Lett.B; Explanations on derivation added; Leading ultrasoft logs included in the analysis (Sec.5);12 pages,4 figures

I review the studies, which were reported after the last Linear Collider Workshop, on top quark physics and QCD physics at a future e+e- linear collider., Comment: 9 pages, 1 figure; Talk given at the International Linear Collider Workshop (LCWS02), Jeju, Korea, Aug. 2002

We compare the perturbatively calculated QCD potential to that obtained from lattice calculations in the theory without light quark flavours. We examine E_tot(r) = 2 m_pole + V_QCD(r) by re-expressing it in the MSbar mass m = m^MSbar(m^MSbar) and by choosing specific prescriptions for fixing the scale mu (dependent on r and m). By adjusting m so as to maximise the range of convergence, we show that perturbative and lattice calculations agree up to 3*r_0 ~ 7.5 GeV^-1 (r_0 is the Sommer scale) within the uncertainty of order Lambda^3 r^2., Comment: Version to appear in Eur.J.Phys; 16 pages, 7 figures

Recently the full O(alpha_S^5 m, alpha_S^5 m log(alpha_S)) correction to the heavy quarkonium 1S energy level has been computed (except the a_3-term in the QCD potential). We point out that the full correction (including the log(alpha_S)-term) is approximated well by the large-beta_0 approximation. Based on the assumption that this feature holds up to higher orders, we discuss why the top quark pole mass cannot be determined to better than O(Lambda_{QCD}) accuracy at a future e^+e^- collider, while the MS-bar mass can be determined to about 40 MeV accuracy (provided the 4-loop MSbar-pole mass relation will be computed in due time)., Comment: LaTeX, 10 pages, 4 eps-figures; Version to appear in Phys. Rev. D, Rapid Communication

We review the recent theoretical progress in heavy quarkonium spectroscopy within the boundstate theory based on perturbative QCD. New microscopic pictures of the heavy quarkonium systems are obtained., Comment: 4 pages, 1 figure

Recently it has been shown that the gross structure of the bottomonium spectrum is reproduced reasonably well within the non-relativistic boundstate theory based on perturbative QCD. In that calculation, however, the fine splittings and the S-P level splittings are predicted to be considerably narrower than the corresponding experimental values. We investigate the bottomonium spectrum within a specific framework based on perturbative QCD, which incorporates all the corrections up to O(alpha_S^5 m_b) and O(alpha_S^4 m_b), respectively, in the computations of the fine splittings and the S-P splittings. We find that the agreement with the experimental data for the fine splittings improves drastically due to an enhancement of the wave functions close to the origin as compared to the Coulomb wave functions. The agreement of the S-P splittings with the experimental data also becomes better. We find that natural scales of the fine splittings and the S-P splittings are larger than those of the boundstates themselves. On the other hand, the predictions of the level spacings between consecutive principal quantum numbers depend rather strongly on the scale mu of the operator \propto C_A/(m_b r^2). The agreement of the whole spectrum with the experimental data is much better than the previous predictions when mu \simeq 3-4 GeV for alpha_S(M_Z)=0.1181. There seems to be a phenomenological preference for some suppression mechanism for the above operator., Comment: 26 pages, 16 figures. Minor changes, to be published in PRD

We calculate O(alpha_S^4 m) and O(alpha_S^4 m log(alpha_S)) corrections to the quarkonium 1S energy level analytically, which have been overlooked in recent studies. These are the contributions from one Coulomb-gluon exchange with the 1-loop vacuum polarization insertion. A part of the corrections was computed numerically some time ago; we correct its error., Comment: RevTeX4, 4 pages, 2 figures; (v2) A crucial reference is included; we correct its error

We study an effect of the off-shellness of the quark and antiquark inside a heavy quarkonium system on IR renormalons contained in the perturbative computations of the quarkonium energy levels. We demonstrate that, when the off-shellness p_Q^2 -m_Q^2 \sim alpha_S^2 m_Q^2 is larger than m_Q Lambda_QCD, renormalons in the energy levels as calculated in perturbative QCD are suppressed by a factor Lambda_QCD/alpha_S^2 m_Q as compared to those in 2 m_pole + V_QCD(r). In this case the residual O(Lambda_QCD^4) renormalon has the same dimension as that of the leading gluon-condensate contribution., Comment: Version to appear in Phys. Lett. B. 12 pages, 1 figure

We examine the total energy E_tot(r) = 2 m_pole + V_QCD(r) of the b\bar b system within perturbative QCD up to O(\alpha_S^3). We extend a previous analysis by incorporating effects of the non-zero charm-quark mass in loops. We find that, once the renormalon cancellation is performed, E_tot(r) agrees well with typical phenomenological potentials for heavy quarkonia at distances 0.5 GeV^-1 ~< r ~< 3 GeV^-1. We also examine the perturbative predictions for E_tot(r) of other heavy quarkonium systems. Whenever stable predictions are obtained, they agree with each other up to an r-independent constant., Comment: 18 pages, 7 figures and 4 tables. Minor changes, 1 reference added, to be publ. in PRD

We study the spectra of the bottomonium and B_c states within perturbative QCD up to order alpha_s^4. The O(Lambda_QCD) renormalon cancellation between the static potential and the pole mass is performed in the epsilon-expansion scheme. We extend our previous analysis by including the (dominant) effects of non-zero charm-quark mass in loops up to the next-to-leading non-vanishing order epsilon^3. We fix the b-quark MSbar mass $\bar{m}_b \equiv m_b^{\bar{\rm MS}}(m_b^{\bar{\rm MS}})$ on Upsilon(1S) and compute the higher levels. The effect of the charm mass decreases $\bar{m}_b$ by about 11 MeV and increases the n=2 and n=3 levels by about 70--100 MeV and 240--280 MeV, respectively. We provide an extensive quantitative analysis. The size of non-perturbative and higher order contributions is discussed by comparing the obtained predictions with the experimental data. An agreement of the perturbative predictions and the experimental data depends crucially on the precise value (inside the present error) of alpha_s(M_Z). We obtain $m_b^{\bar{\rm MS}}(m_b^{\bar{\rm MS}}) = 4190 \pm 20 \pm 25 \pm 3 ~ {\rm MeV}$., Comment: 33 pages, 21 figures; v2: Abstract modified; Table7 (summary of errors) added; Version to appear in Phys.Rev.D

The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider, Comment: 192 pages, 131 figures. Some figures have reduced quality. Full quality figures can be obtained from http://tesla.desy.de/tdr. Editors - R.-D. Heuer, D.J. Miller, F. Richard, P.M. Zerwas

We report new aspects of the recent theoretical progress in heavy quarkonium physics. (1) Contrary to wide beliefs, the gross structure of the bottomonium spectrum is described well by the non-relativistic boundstate theory based on perturbative QCD. (2) This leads to a new physical picture of the bottomonium states: the boundstate mass is composed mainly of the self-energies of b and bbar accumulated inside the boundstate. (3) A connection to the conventional phenomenological potential-model approaches is provided., Comment: 20 pages, 10 figures, Talk given at ``Accelerator and Particle Physics Institute (APPI 2001)'', Morioka, Japan, Feb. 20--22, 2001

When the cancellation of the leading renormalon contributions is incorporated, the total energy of a b bbar system, E_{tot,bbbar}(r) = 2 m_{pole,b} + V_QCD(r), agrees well with the potentials used in phenomenological models for heavy quarkonia in the range 0.5 GeV^-1 < r < 3 GeV^-1. We provide a connection between the conventional potential-model approaches to the quarkonium spectroscopy and the recent computation based on perturbative QCD., Comment: 16 pages, 6 figures;v2:One table added, Fig.2(a) and Fig.3 modified, some remarks added, no change in major discussion or conclusions;v3:comments on effective theories added, comparison with BLM scale added, references added

We study the energy spectrum of bottomonium in perturbative QCD, taking alpha_s(Mz)=0.1181 +/- 0.0020 as input and fixing m_b^{MSbar}(m_b^{MSbar}) on the Upsilon(1S) mass. Contrary to wide beliefs, perturbative QCD reproduces reasonably well the gross structure of the spectrum as long as the coupling constant remains smaller than one. We perform a detailed analysis and discuss the size of non-perturbative effects. A new qualitative picture on the structure of the bottomonium spectrum is provided. The lowest-lying (c,cbar) and (b,cbar) states are also examined., Comment: 12 pages, 2 figures; Discussion on ultra-soft effects included; Some conservative error estimates added; Version to appear in Phys.Lett.B

The top quark mass will be determined to high accuracy from the shape of the ttbar total production cross section in the threshold region at a future linear e+e- collider. Presently the estimated statistical error in the measurement of the MSbar mass of the top quark is \sim 50 MeV, while the estimated theoretical error is 150-200 MeV. In order to reduce the theoretical uncertainty to below 50 MeV, we have recently computed an important part of the higher-order corrections. We deomonstrate the significance of the calculated correction., Comment: 5 pages, 2 figures, Talk given at the Linear Colliders Workshop 2000, Fermilab, USA, October 2000

We report our theoretical study on how to probe the anomalous CP-violating couplings of the top quark in the ttbar region at future e+e- linear colliders. We focus on the unique role of the ttbar threshold region., Comment: 11 pages, 6 figures. Talk given at the Kiken Meeting: ``New Perspectives in Elementary Particle Physics'', Kyoto, Japan, July 17 - 20, 2000

Presently the quarkonium spectrum, written in terms of the quark MSbar-mass, is known at O(alpha_s^3 m) accuracy. We point out that in order to achieve O(alpha_s^4 m) accuracy it is sufficient to calculate further (I) the O(alpha_s^4 m) relation between the MSbar-mass and the pole-mass, and (II) the binding energy at O(alpha_s^5 m) in the large-beta_0 approximation. We calculate the latter correction analytically for the 1S-state and study its phenomenological implications., Comment: Version to appear in Phys. Lett. B. 9 pages. No figure

We investigate gauge dependence of a nonrelativistic boundstate formalism used in contemporary calculations. It is known that the effective Hamiltonian of the boundstate system depends on the choice of gauge. We obtain the gauge transformation charge of the Hamiltonian, by which gauge independence of the mass spectrum and gauge dependences of the boundstate wave functions are dictated. We raise two questions of practical and physical interest, and provide answers to them., Comment: 5 pages, no figure

This is an elementary introduction to the recent significant theoretical progress in the field of heavy quarkonium physics. We show how renormalon cancellation takes place in the heavy quarkonium system, such as bottomonium and (remnant of) toponium resonance, and how this notion is useful in extracting the MSbar masses of the bottom and top quarks., Comment: Based on the invited talk given at the Japan Physics Society Meeting, Osaka, Japan, March 30 - April 2, 2000

We study how to probe the anomalous CP-violating couplings of top quark with photon, Z and gluon in the ttbar threshold region at future e+e- colliders. These couplings contribute to the difference of the t and tbar polarization vectors delta P and to the CP-odd spin correlation tensor delta Q_ij. We find that typical sizes of delta P and delta Q_ij are 5-20% times the couplings (d_tgamma, d_tZ, d_tg) in the threshold region. Experimentally delta P can be measured efficiently using the CP-odd combination of the l+/l- momenta or of the l+/l- directions. We have similar sensitivities to both the real and imaginary parts of the couplings independently using the two components of delta P. Taking advantage of different dependences of delta P on the e+/e- polarizations and on the c.m. energy, we will be able to disentangle the effects of the three couplings d_tgamma, d_tZ, d_tg in the ttbar threshold region. We give rough estimates of sensitivities to the anomalous couplings expected at future e+e- colliders. The sensitivities to d_tgamma and d_tZ are comparable to those attainable in the open-top region at e+e- colliders. The sensitivity to d_tg is worse than that expected at a hadron collider but exceeds the sensitivity in the open-top region at e+e- colliders., Comment: 25 pages, 9 figures

Using non-relativistic effective theories, new next-to-next-to-leading order (NNLO) QCD corrections to the total $t\bar t$ production cross section at the Linear Collider have been calculated recently. In this article the NNLO calculations of several groups are compared and the remaining uncertainties are discussed. The theoretical prospects for an accurate determination of top quark mass parameters are discussed in detail. An outlook on possible future improvements is given., Comment: 21 pages, latex, 8 postscript figures included, contribution to the Proceedings of the 2nd joint ECFA/DESY Workshop on Physics Studies for a Future Linear Collider

I review the theoretical progress made in these 4 years concerning the process e+e- -> ttbar in the threshold region. I summarize the progress towards each of the three major physics goals that should be achieved at ttbar threshold region., Comment: Talk given at the International Workshop on Linear Colliders, April 28 - May 5, 1999, Sitges, Spain

A nonrelativistic boundstate formalism used in contemporary calculations is investigated. It is known that the effective Hamiltonian of the boundstate system depends on the choice of gauge. We obtain the transformation charge Q of the Hamiltonian for an arbitrary infinitesimal change of gauge, by which gauge independence of the mass spectrum and gauge dependences of the boundstate wave functions are dictated. We give formal arguments based on the BRST symmetry supplemented by power countings of Coulomb singularities of diagrams. For illustration: (1)we calculate Q up to O(1/c), (2)we examine gauge dependences of diagrams for a decay of a qqbar boundstate up to O(1/c) and show that cumbersome gauge cancellations can be circumvented by directly calculating Q. As an application we point out that the present calculations of top quark momentum distribution in the ttbar threshold region are gauge dependent. We also show possibilities for incorrect calculations of physical quantities of boundstates when the on-shell matching procedure is employed. We give a proof of a justification for the use of the equation of motion to simplify the form of a local NRQCD Lagrangian. The formalism developed in this work will provide useful cross checks in computations involving NRQED/NRQCD boundstates., Comment: 30 pages, 15 figures (ver1); Presentations of Introduction and Conclusion were modified substantially, although none of our findings have been changed; Side remarks have been added in various parts of the paper. (ver2); Supplementary remarks and minor corrections (ver3)

Solar and atmospheric neutrino anomalies are described by bimaximal mixing of three neutrinos. Neutrino oscillations in appearance nu_e <--> nu_mu,nu_tau and in disappearance nu_e long baseline and atmospheric experiments are sensitive to deviations from the ideal bimaximal mixing. It is suggested that these deviations may be dominated by a rotation in the electron--muon plane of the generation space. Simple seesaw models are described supporting this idea. The rotation angle is estimated from Fritzsch's relation. Predictions are presented for oscillations in long baseline experiments, for solar neutrinos, and for the rates of neutrinoless double beta decays., Comment: Latex, 13 p., no figures