Search

During 2011 the LHCb experiment at CERN collected 1.0 fb-1 of sqrt{s} = 7 TeV pp collisions. Due to the large heavy quark production cross-sections, these data provide unprecedented samples of heavy flavoured hadrons. The first results from LHCb have made a significant impact on the flavour physics landscape and have definitively proved the concept of a dedicated experiment in the forward region at a hadron collider. This document discusses the implications of these first measurements on classes of extensions to the Standard Model, bearing in mind the interplay with the results of searches for on-shell production of new particles at ATLAS and CMS. The physics potential of an upgrade to the LHCb detector, which would allow an order of magnitude more data to be collected, is emphasised., Comment: v2: 180 pages; many figures. Updated for submission to EPJC; v3: published version

The Proceedings of the 2003 SLAC Workshops on flavor physics with a high luminosity asymmetric e+e- collider. The sensitivity of flavor physics to physics beyond the Standard Model is addressed in detail, in the context of the improvement of experimental measurements and theoretical calculations., Comment: 476 pages. Printed copies may be obtained by request to kwebb@slac.stanford.edu . arXiv admin note: v2 appears to be identical to v1

We show that an angular analysis of B --> V1 V2 decays yields numerous tests for new physics in the decay amplitudes. Unlike direct CP asymmetries, many of these new-physics observables are nonzero even if the strong phase differences vanish. For certain observables, neither time-dependent measurements nor tagging is necessary. Should a signal for new physics be found, one can place a lower limit on the size of the new-physics parameters, as well as on their effect on the measurement of the phase of B0--Bbar0 mixing., Comment: 9 pages, plain latex, no figures. Title modified slightly. Paragraph added about viability of method. Conclusions unchanged. To be published in Europhysics Letters

Direct CP violation in B -> J/Psi K is a clean test for new physics. However, the direct CP asymmetry will vanish if the new-physics amplitude has the same strong phase as the standard-model amplitude. We show that this type of new physics can still be detected via an angular analysis of the sister decay mode B -> J/Psi K^*. Time-dependent measurements and tagging are not necessary. Should new physics be found, this angular analysis can be used to obtain information about the size of the new-physics parameters., Comment: 6 pages, LaTeX, no figures. Talk given by Rahul Sinha at Flavor Physics and CP Violation (FPCP), Philadelphia, PA, USA, May 2002

We describe a new method for extracting weak, CP-violating phase information, with no hadronic uncertainties, from an angular analysis of B -> V_1 V_2 decays, where V_1 and V_2 are vector mesons. The quantity $\sin^2 (2 \phi_1 + \phi_3)$ (\phi_1=\beta and \phi_3=\gamma) can be cleanly obtained from the study of decays such as B_d^0(t) -> D^{*\pm} \rho^\mp, D^{*\pm} a_1^{\mp}, D^{*0} K^{*0}, etc. Similarly, one can use B_s^0(t) -> D_s^{*\pm} K^{*\mp} or even B\pm -> D^{*0}K^*\pm to extract $\sin^2 \phi_3$. There are no penguin contributions to these decays. It is possible that $\sin^2 (2\phi_1 + \phi_3)$ will be the second function of CP phases, after $\sin 2\phi_1$, to be measured at B-factories., Comment: 4 pages, LaTeX, 1 figure. Uses two-column style file ltwol.sty. To be published in the Proceedings of the Fourth International Workshop on B Physics and CP Violation, Ise-Shima, Japan, February 18 - 23, 2001

We show how B -> pi pi decays can be used to search for new physics in the b -> d flavour-changing neutral current. One needs one piece of theoretical input, which we take to be a prediction for P/T, the ratio of the penguin and tree amplitudes in Bd -> pi+ pi-. If present, new physics can be detected over most of the parameter space. If \alpha (\phi_2) can be obtained independently, measurements of B+ -> pi+ pi0 and Bd/Bd(bar) -> pi0 pi0 are not even needed., Comment: 4 pages, LaTeX, 1 figure. Uses two-column style file ltwol.sty. To be published in the Proceedings of the Fourth International Workshop on B Physics and CP Violation, Ise-Shima, Japan, February 18 - 23, 2001

Present experiments in pursuit of the mass difference in the Bs-Bs(bar) system have put a lower bound on this quantity of $\Delta M_s > 14.9 ps^{-1}$ (at 95% C.L.). The same experiments also yield a local minimum in the log-likelihood function around $\Delta M_s = 17.7 ps^{-1}$, which is $2.5\sigma$ away from being zero. Motivated by these observations, we investigate the consequences of a possible measurement of $\Delta M_s = 17.7 \pm 1.4 ps^{-1}$, in the context of both the standard model and supersymmetric models with minimal flavor violation. We perform a fit of the quark mixing parameters in these theories and estimate the expected ranges of the CP asymmetries in B decays, characterized by $\alpha$, $\beta$ and $\gamma$, the interior angles of the CKM-unitarity triangle. Based on this study, we argue that, if indeed $\Delta M_s$ turns out to be in its currently-favored range, this would disfavor a large class of supersymmetric models. Indeed, of all the models examined here, the best fit to the data occurs for the standard model., Comment: 14 pages, LaTeX, 8 figures, corrected some typos. Accepted for publication in Eur. Phys. J. C

It is well known that one can use B -> pi pi decays to probe the CP-violating phase \alpha. In this paper we show that these same decays can be used to search for new physics. This is done by comparing two weak phases which are equal in the standard model: the phase of the t-quark contribution to the b -> d penguin amplitude, and the phase of Bd-Bd(bar) mixing. In order to make such a comparison, we require one piece of theoretical input, which we take to be a prediction for |P/T|, the relative size of the penguin and tree contributions to Bd -> pi^+ pi^-. If independent knowledge of \alpha is available, the decay Bd(t) -> pi^+ pi^- alone can be used to search for new physics. If a full isospin analysis can be done, then new physics can be found solely through measurements of B -> pi pi decays. The most promising scenario occurs when the isospin analysis can be combined with independent knowledge of \alpha. In all cases, the prospects for detecting new physics in B -> pi pi decays can be greatly improved with the help of additional measurements which will remove discrete ambiguities., Comment: 24 pages, LaTeX, 3 figures

Recently, a scenario has been proposed in which the gravitational scale could be as low as the TeV scale, and extra dimensions could be large and detectable at the electroweak scale. Although supersymmetry is not a requirement of this scenario, it is nevertheless true that its best-motivated realizations arise in supersymmetric theories (like M theory). We argue here that supersymmetry can have robust, and in some instances fatal, implications for the expected experimental signature for TeV-scale gravity. The signature of the supersymmetric version of the scenario differs most dramatically from what has been considered in the literature because mass splittings within the gravity supermultiplet in these models are extremely small, implying in particular the existence of a very light spin-one superpartner for the graviton. We compute the implications of this graviphoton, and show that it can acquire dimension-four couplings to ordinary matter which can strongly conflict with supernova bounds., Comment: 31 pages, LaTeX, 7 figures, text slightly rewritten, figures updated, conclusions unchanged

We argue that one can search for physics beyond the standard model through measurements of the isospin-violating quantity $\Delta^{-0} \equiv \Gamma(B^- \to \rho^- \gamma)/2\Gamma(B^0 \to \rho^0 \gamma)-1$, its charge conjugate $\Delta^{+0}$, and direct CP violation in the partial decay rates of $B^\pm \to \rho^\pm \gamma$. We illustrate this by working out theoretical profiles of the charge-conjugate averaged ratio $\Delta \equiv {1 \over 2}(\Delta^{+0} +\Delta^{-0})$ and the CP asymmetry $A_{CP}(B^\pm \to \rho^\pm \gamma)$ in the standard model and in some variants of the minimal supersymmetric standard model. We find that chargino contributions in the large $\tan \beta$ region may modify the magnitudes and flip the signs of $\Delta$ and $A_{CP}(B^\pm \to \rho^\pm \gamma)$ compared to their standard-model values, providing an unmistakeable signature of supersymmetry., Comment: 10 pages, 7 figures (requires graphicx)

We study T-violating triple-product asymmetries in the quark-level decay b -> s u u(bar) within the standard model (SM). We find that only two types of triple products are non-negligible. The asymmetry in p_u . [s_u x s_u(bar)] or p_u(bar) . [s_u x s_u(bar)] can be as large as about 5%. It can be probed in B -> V_1 V_2 decays, where V_1 and V_2 are vector mesons. And the asymmetry in s_b . [p_u x p_s] can be in the range 1%--3%. One can search for this signal in the decay \Lambda_b -> \Lambda \pi^+ \pi^- or in B^* -> X_s X, where X_s and X then each decay into two mesons. All other triple-product asymmetries are expected to be small within the SM. This gives us new methods of searching for new physics., Comment: 14 pages, LaTeX, no figures

The $b\to d$ penguin amplitude receives contributions from internal $u$, $c$ and $t$-quarks. We show that it is impossible to measure the weak phase of any of these penguin contributions without theoretical input. However, a single assumption involving the hadronic parameters makes it possible to obtain the weak phase and test for the presence of new physics in the $b\to d$ flavour-changing neutral current., Comment: 4 pages, latex, no figures, talk given by R. Sinha at the 3rd International Conference on B Physics and CP Violation, Taipei, Taiwan, December 3-7, 1999, to appear in the Proceedings

The first measurements of CP violation in the $B$ system will likely probe $\sin 2\alpha$, $\sin 2\beta$ and $\cos 2\gamma$. Assuming that the CP angles $\alpha$, $\beta$ and $\gamma$ are the interior angles of the unitarity triangle, these measurements determine the angle set $(\alpha,\beta,\gamma)$ except for a twofold discrete ambiguity. If one allows for the possibility of new physics, the presence of this discrete ambiguity can make its discovery difficult: if only one of the two candidate solutions is consistent with constraints from other measurements in the $B$ and $K$ systems, one is not sure whether new physics is present or not. We review the methods used to resolve the discrete ambiguity and show that, even in the presence of new physics, they can usually be used to uncover this new physics. There are some exceptions, which we describe in detail. We systematically scan the parameter space and present examples of values of $(\alpha,\beta,\gamma)$ and the new-physics parameters which correspond to all possibilities. Finally, we show that if one relaxes the assumption that the bag parameters $\BBd$ and $\BK$ are positive, one can no longer definitively establish the presence of new physics., Comment: 29 pages, LaTeX, 1 figures, presentation substantially reworked, physics conclusions unchanged. This version will be published in Phys. Rev. D

We (re)examine CP violation in the decays B_d -> D K_s, where D represents D^0, D(bar), or one of their excited states. The quantity $\sin^2(2\beta + \gamma)$ can be extracted from the time-dependent rates for $B_d(t) -> {\bar D}^{**0} K_s$ and $B_d(t) -> D^{**0} K_s$, where the $D^{**0}$ decays to $D^{(*)+}\pi^-$. If one considers a non-CP-eigenstate hadronic final state to which both D(bar) and D^0 can decay (e.g. $K^+\pi^-$), then one can obtain two of the angles of the unitarity triangle from measurements of the time-dependent rates for $B_d(t) -> (K^+\pi^-)_{D K_s}$ and $B_d(t) -> (K^-\pi^+)_{D K_s}$. There are no penguin contributions to these decays, so all measurements are theoretically clean., Comment: 15 pages, LaTeX, no figures

I review the prospects for the detection of Delta L=2 processes at future colliders. Except in contrived models, the process e- e- -> W- W- is unobservable at future linear colliders unless $\sqrt{s} \gsim 2$ TeV, due to constraints from neutrinoless double beta decay. As there are no analogous constraints on the Majorana mass of the $\nu_\mu$, mu- mu- -> W- W- could be observed at a muon collider with considerably lower $\sqrt{s}$. One can also consider esoteric processes such as gamma gamma -> mu+ mu+ W- W-. Such processes may be observable if $\sqrt{s} \gsim 4$ TeV., Comment: 7 pages, 3 figures; talk given at Beyond the Desert -- Accelerator, Non-Accelerator and Space Approaches into the Next Millenium}, Castle Ringberg, Tegernsee, Germany, June 1999

There are variety of methods which directly test for the presence of new physics in the b -> s flavour-changing neutral current (FCNC), but none which cleanly probe new physics in the b -> d FCNC. One possible idea is to compare the weak phase of the t-quark contribution to the b -> d penguin, which is $-\beta$ in the SM, with that of Bd-Bd(bar) mixing ($-2\beta$ in the SM). In this talk I show that, in fact, it is impossible to measure the weak phase of the t-quark penguin, or indeed any penguin contribution, without theoretical input. However, if one makes a single assumption involving the hadronic parameters, it is possible to obtain the weak phase. I discuss how one can apply such an assumption to the time-dependent decays $Bd(t) -> K0 K0(bar)$ and $Bs(t) -> \phi K_s$ in order to detect new physics in the b -> d FCNC., Comment: 8 pages, 2 figures; talk given at MRST '99: High Energy Physics at the Millenium}, Carleton University, Ottawa, Canada, May 1999

The b -> d penguin amplitude receives contributions from internal u, c and t-quarks. We show that it is impossible to measure the weak phase of any of these penguin contributions without theoretical input. However, it is possible to obtain the weak phase if one makes a single assumption involving the hadronic parameters. With such an assumption, one can test for the presence of new physics in the b -> d flavour-changing neutral current by comparing the weak phase of B_d^0-{\bar B}_d^0 mixing with that of the t-quark contribution to the b -> d penguin., Comment: 20 pages, no figures

Time-dependent measurements of the decays B_s^0(t)-->\phi K_s and B_d^0(t) --> K^0 \bar{K}^0 can be used to compare the weak phases of B_d^0-\bar{B}_d^0 mixing and the t-quark contribution to the b->d penguin. Since these two phases are equal in the standard model, any discrepancy would be a sign of new physics, specifically in the b->d flavour-changing neutral current (FCNC). The method can be applied to other pairs of decays, such as B_s^0(t)--> J/\Psi K_s and B_d^0(t)--> J/\Psi \pi^0., Comment: 16 pages, LaTeX, Modified and accepted for publication in Phys.Lett.B

We report on a comparative study of the profile of the CKM unitarity triangle, and the resulting CP asymmetries in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), characterized by a single phase in the quark flavour mixing matrix. The supersymmetric contributions to the mass differences \Delta M_d, \Delta M_s and to the CP-violating quantity |\epsilon| are, to an excellent approximation, equal to each other in these theories, allowing for a particularly simple way of implementing the resulting constraints on the elements of V_{CKM} from the present knowledge of these quantities. Incorporating the next-to-leading-order corrections and applying the current direct and indirect constraints on the supersymmetric parameters, we find that the predicted ranges of \sin 2 \beta in the standard model and in MSSM models are very similar. However, precise measurements at B-factories and hadron machines may be able to distinguish these theories in terms of the other two CP-violating phases \alpha and \gamma. This is illustrated for some representative values of the supersymmetric contributions in \Delta M_d, \Delta M_s and |\epsilon|., Comment: 30 pages, 9 figures; typos corrected, minor notation change; matches version to appear in the European Physical Journal C

We examine, as model-independently as possible, the production of bileptons at hadron colliders. When a particular model is necessary or useful, we choose the 3-3-1 model. We consider a variety of processes: q anti-q -> Y^{++} Y^{--}, u anti-d -> Y^{++} Y^{-}, anti-u d -> Y^+ Y^{--}, q anti-q -> Y^{++} e^{-} e^{-}, q anti-q -> phi^{++} phi^{--}, u anti-d -> -> phi^{++} phi^{-}, and anti-u d -> phi^{+} phi^{--}, where Y and phi are vector and scalar bileptons, respectively. Given the present low-energy constraints, we find that at the Tevatron, vector bileptons are unobservable, while light scalar bileptons (M_phi <= 300 GeV) are just barely observable. At the LHC, the reach is extended considerably: vector bileptons of mass M_Y <= 1 TeV are observable, as are scalar bileptons of mass M_phi <= 850 GeV., Comment: 20 pages (LATEX), 7 figures, minor modifications

Dighe, Gronau and Rosner have shown that, by assuming SU(3) flavor symmetry and first-order SU(3) breaking, it is possible to extract the CP angles \alpha and \gamma from measurements of the decay rates of B_d^0(t) --> \pi^+\pi^-, B_d^0 --> \pi^- K^+ and B^+ --> \pi^+ K^0, along with their charge-conjugate processes. We extend their analysis to include the SU(3)-related decays B_s^0 --> \pi^+ K^-, B_s^0(t) --> K^+ K^- and B_s^0 --> K^0 {\bar K^0}. There are several advantages to this extension: discrete ambiguities are removed, fewer assumptions are necessary, and the method works even if all strong phases vanish. In addition, we show that \gamma can be obtained cleanly, with no penguin contamination, by using the two decays B_s^0(t) --> K^+ K^- and B_s^0 --> K^0 {\bar K^0}., Comment: 28 pages, LaTeX

We review and update the effects of physics beyond the standard model on CP asymmetries in B decays. These asymmetries can be significantly altered if there are important new-physics contributions to \bqbqbar mixing. This same new physics will therefore also contribute to rare, flavor-changing B decays. Through a study of such decays, we show that it is possible to partially distinguish the different models of new physics., Comment: 42 pages, plain TeX (macros included), 1 figure (included). A few sentences added, references updated. Present manuscript is now identical to the version accepted for publication in Phys. Rev. D

We review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP asymmetries in $B$ decays, taking into account recent experimental and theoretical developments. With the updated CKM matrix we present the currently-allowed range of the ratios $|V_{td}/V_{ts}|$ and $|V_{td}/V_{ub}|$, as well as the standard model predictions for the \bsbsbar\ mixing parameter $\xs$ (or, equivalently, $\delms$) and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize the CP-asymmetries in $B$-decays., Comment: 23 pages, LaTeX, 9 figures; updated to include latest experimental results on Bs-Bs(bar) mixing

We survey the implications for new physics of the discrepancy between the LEP measurement of $R_b$ and its Standard Model prediction. Two broad classes of models are considered: ($i$) those in which new $Z\bbar b$ couplings arise at tree level, through $Z$ or $b$-quark mixing with new particles, and ($ii$) those in which new scalars and fermions alter the $Z \bbar b$ vertex at one loop. We keep our analysis as general as possible in order to systematically determine what kinds of features can produce corrections to $R_b$ of the right sign and magnitude. We are able to identify several successful mechanisms, which include most of those which have been recently been proposed in the literature, as well as some earlier proposals (\eg\ supersymmetric models). By seeing how such models appear as special cases of our general treatment we are able to shed light on the reason for, and the robustness of, their ability to explain $R_b$., Comment: 60 pages, 8 figures, plain tex, uses epsf. Final version to appear in Phys. Rev. D; propgating sign error corrected in eqs. 78, 87, 88, 89, 98, and 107; results unchanged

We critically reexamine the prospects for the observation of the $\Delta L=2$ lepton-number-violating process $\eeWW$ using the $e^-e^-$ option of a high-energy $e^+e^-$ collider (NLC). We find that, except in the most contrived scenarios, constraints from neutrinoless double beta decay render the process unobservable at an NLC of $\sqrt{s}<2$ TeV. Other $\Delta L=2$ processes such as $\ggllww$, $\egnllw$, $\eennll$ ($\ell=\mu,\tau$), and $\egeww$, which use various options of the NLC, require a $\sqrt{s}$ of at least 4 TeV for observability., Comment: paper in LATEX, 24 pages, 10 figures in separate uuencoded psfile. Complete psfile available via anonymous ftp at ftp://lapphp0.in2p3.fr/pub/preprints-theorie/doublebeta.uu or via www at http://lapphp0.in2p3.fr/preplapp/psth/doublebeta.ps.gz

We review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP asymmetries in $B$ decays, taking into account recent experimental and theoretical developments. In performing our fits, we use inputs from the measurements of the following quantities: (i) $\abseps$, the CP-violating parameter in $K$ decays, (ii) $\delmd$, the mass difference due to the \bdbdbar\ mixing, (iii) the matrix elements $\absvcb$ and $\absvub$, (iv) $B$-hadron lifetimes, and (v) the top quark mass. The experimental input in points (ii) - (v) has improved compared to our previous fits. With the updated CKM matrix we present the currently-allowed range of the ratios $|V_{td}/V_{ts}|$ and $|V_{td}/V_{ub}|$, as well as the standard model predictions for the \bsbsbar\ mixing parameter $\xs$ (or, equivalently, $\delms$) and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize the CP-asymmetries in $B$-decays. Various theoretical issues related to the so-called ``penguin-pollution," are of importance for the determination of the phases $\alpha$ and $\gamma$ from the CP-asymmetries in $B$ decays, are also discussed. (to be published in the proc. of the Pisa heavy flavour physics conference.), Comment: 25 pages, 9 figures (uses psfig.sty)

We discuss the direct measurement of the trilinear vector boson couplings in present and future collider experiments. The major goals of such experiments will be the confirmation of the Standard Model (SM) predictions and the search for signals of new physics. We review our current theoretical understanding of anomalous trilinear gauge boson self-interactions. If the energy scale of the new physics is $\sim 1$ TeV, these low energy anomalous couplings are expected to be no larger than ${\cal O}(10^{-2})$. Constraints from high precision measurements at LEP and low energy charged and neutral current processes are critically reviewed., Comment: 53 pages with 17 embedded figures, LaTeX, uses axodraw.sty, figures available on request. The complete paper, is available at ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-871.ps.Z or http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-871.ps.Z Summary of the DPF Working Subgroup on Anomalous Gauge Boson Interactions of the DPF Long Range Planning Study

Motivated by the recent determination of the top quark mass by the CDF collaboration, $\mt =174 \pm 10 ^{+13}_{-12}$ GeV, we review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model. In performing our fits, we use inputs from the measurements of the following quantities: (i) $\abseps$, the CP-violating parameter in $K$ decays, (ii) $\delmd$, the mass difference due to the \bdbdbar\ mixing, (iii) the matrix elements $\absvcb$ and $\absvub$, and (iv) $B$-hadron lifetimes. We find that the allowed region of the unitarity triangle is very large, mostly due to theoretical uncertainties. (This emphasizes the importance of measurements of CP-violating rate asymmetries in the $B$ system.) Nevertheless, the present data do somewhat restrict the allowed values of the coupling constant product $f_{B_d}\sqrt{\hat{B}_{B_d}}$ and the renormalization-scale invariant bag constant $\hat{B}_K$. With the updated CKM matrix we present the currently-allowed range of the ratio $\vert V_{td}/V_{ts} \vert$, as well as the standard model predictions for the \bsbsbar\ mixing parameter $\xs$ and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize the CP-asymmetries in $B$-decays. The ALEPH collaboration has recently reported a significant improvement on the lower limit on the $\bs$-$\bsb$ mass difference, $\Delta M_s/\Delta M_d > 11.3$ (95\% C.L.). This has interesting consequences for the CKM parameters which are also worked out. NOTE: this is a revised and updated version of our previous paper., Comment: LaTeX, 27 pages, 16 uuencoded figures (enclosed), CERN-TH.7398/94, UdeM-GPP-TH-94-06

If the Standard Model explanation of CP violation is correct, then measurements of CP-violating asymmetries in $B$ meson decays can in principle determine the entire quark mixing matrix., Comment: 8 pages (plain TeX), 1 figure (postscript file appended), DAPNIA/SPP 94-06, NSF-PT-94-2, UdeM-LPN-TH-94-189

We calculate the cross sections for the single production of doubly-charged dileptons, both scalar and vector, at $e^+e^-$, $e\gamma$ and $\gamma\gamma$ colliders at $\sqrt{s}=500$ GeV and 1 TeV. The $e\gamma$ mode is by far the most promising -- dileptons whose coupling is as weak as $O(10^{-4})\alpha_{em}$ can be observed, for masses virtually up to the kinematic limit. Dileptons of mass up to $\sqrt{s}$ can also be seen in $e^+e^-$ and $\gamma\gamma$ colliders, for couplings of order $\alpha_{em}$. In all three colliders, most of the cross section comes from events in which the only particles detected are $e^-e^-$, the decay products of the dilepton, yielding an unmistakeable experimental signature., Comment: plain TeX, 9 pages + 13 figures (not included, but available upon request), UdeM-LPN-TH-94-190, McGill-94/12

After reviewing techniques for extracting clean information on CP-violating phase angles from $B$ decays, we explain the rules for finding decay modes that can probe the phase angle $\gamma$ of the unitarity triangle. We identify the more promising of these ``$\gamma$ modes,'' estimate their branching ratios, and examine the degree to which they are theoretically clean. We then show that when the quark mixing matrix is not approximated as usual, but is treated exactly, none of the ``$\gamma$ modes'' actually measures $\gamma$. Rather, each of them measures $\gamma$ plus some correction. In all modes, the correction is small enough to be disregarded in first-generation experiments, but in some of them, it may be large enough to be observed in second-generation experiments. Our treatment of the $\gamma$ modes calls attention to the fact that when the quark mixing matrix is treated exactly, there are six unitarity triangles, rather than just one triangle. However, only four of the angles in these six triangles are independent. Examining the role played by these four angles, we discover that, in principle at least, measurements of nothing but CP-violating asymmetries in $B$ decays are sufficient to determine the entire quark mixing matrix., Comment: LaTeX, 18 pages, 11 figures (not included, available upon request), talk given by B. Kayser at the Workshop on B Physics at Hadron Accelerators, Snowmass, Colorado, June 21-July 2, 1993, DAPNIA/SPP 93-23, NSF-PT-93-4, UdeM-LPN-TH-93-184

Using effective-lagrangian techniques we perform a systematic survey of the lowest-dimension effective interactions through which heavy physics might manifest itself in present experiments. We do not restrict ourselves to special classes of effective interactions (such as `oblique' corrections). We compute the effects of these operators on all currently well-measured electroweak observables, both at low energies and at the $Z$ resonance, and perform a global fit to their coefficients. Despite the fact that a great many operators arise in our survey, we find that most are quite strongly bounded by the current data. We use our survey to systematically identify those effective interactions which are {\it not} well-bounded by the data -- these could very well include large new-physics contributions. Our results may also be used to efficiently confront specific models for new physics with the data, as we illustrate with an example., Comment: plain TeX, 68 pages, 2 figures (postscript files appended), McGill-93/12, NEIPH-93-008, OCIP/C-93-6, UQAM-PHE-93/08, UdeM-LPN-TH-93-155

The single production of leptoquarks in $e^+e^-$, $e\gamma$ and $\gamma \gamma$ linear colliders is discussed. We show that these new particles could be seen in such machines even if their mass is close to the kinematic limit. (Invited talk given by G.B. at the ``Workshop on Physics and Experiments at Linear $e^+e^-$ Colliders'', Waikoloa, Hawaii, April 26-30, 1993.), Comment: 5 pages, LaTeX, 3 figures (not included, but available upon request), UdeM-LPN-TH-93-160, McGill-93/29

The STU formalism of Peskin and Takeuchi is an elegant method for encoding the measurable effects of new physics which couples to light fermions dominantly through its effects on electroweak boson propagation. However, this formalism cannot handle the case where the scale of new physics is not much larger than the weak scale. In this case three new parameters (V, W and X) are required. We perform a global fit to precision electroweak data for these six parameters. Our results differ from what is found for just STU. In particular we find that the preference for S < 0 is not maintained., Comment: Plain TeX, 11 pages, one figure (ps file enclosed), (replaced version corrects minor TeX problem, text unchanged) UdeM-LPN-TH-93-166, McGill-93/24, OCIP/C-93-9

We consider single production of leptoquarks (LQ's) at $e^+e^-$ and $\gamma\gamma$ colliders, for two values of the centre-of-mass energy, $\sqrt{s}=500$ GeV and 1 TeV. We find that LQ's which couple within the first generation are observable for LQ masses almost up to the kinematic limit, both at $e^+e^-$ and $\gamma\gamma$ colliders, for the LQ coupling strength equal to $\alpha_{em}$. The cross sections for single production of $2^{nd}$- and $3^{rd}$-generation LQ's at $e^+e^-$ colliders are too small to be observable. In $\gamma\gamma$ collisions, on the other hand, $2^{nd}$-generation LQ's with masses much larger than $\sqrt{s}/2$ can be detected. However, $3^{rd}$-generation LQ's can be seen at $\gamma\gamma$ colliders only for masses at most $\sim\sqrt{s}/2$, making their observation more probable via the pair production mechanism., Comment: plain TeX, 14 pages, 6 figures (not included but available on request), some minor changes to the text, one reference added, figures and conclusions unchanged, UdeM-LPN-TH-93-152, McGill-93/23