Unitarity Triangle Analysis in the Standard Model and Sensitivity to New Physics

By using the most recent determinations of the several theoretical and experimental input parameters, we update the Unitarity Triangle analysis in the Standard Model and discuss the sensitivity to New Physics effects. We investigate the interest of measuring with a better precision the various physical quantities entering the Unitarity Triangle analysis and study in a model independent way whether, despite the undoubted success of the CKM mechanism in the Standard Model, the Unitarity Triangle analysis still allows the presence of New Physics.Comment: Invited talk at the Workshop on the CKM Unitarity Triangle, IPPP Durham, April 2003 (eConf C0304052). 9 pages LaTeX, 15 eps figures. Misprint corrected and references adde

Direct CP Violation in B->phi K_s and New Physics

In the presence of large New Physics contributions to loop-induced b->s transitions, sizable direct CP violation in B-> phi K decays is expected on general grounds. We compute explicitly CP-violating effects using QCD factorization and find that, even in the restricted case in which New Physics has the same penguin structure as the Standard Model, the rate asymmetry can be of order one. We briefly discuss a more general scenario and comment on the inclusion of power-suppressed corrections to factorization.Comment: 3 page

The UTfit Collaboration Report on the Status of the Unitarity Triangle beyond the Standard Model I. Model-independent Analysis and Minimal Flavour Violation

Starting from a (new physics independent) tree level determination of rhobar and etabar, we perform the Unitarity Triangle analysis in general extensions of the Standard Model with arbitrary new physics contributions to loop-mediated processes. Using a simple parameterization, we determine the allowed ranges of non-standard contributions to |Delta F|=2 processes. Remarkably, the recent measurements from B factories allow us to determine with good precision the shape of the Unitarity Triangle even in the presence of new physics, and to derive stringent constraints on non-standard contributions to |Delta F|=2 processes. Since the present experimental constraints favour models with Minimal Flavour Violation, we present the determination of the Universal Unitarity Triangle that can be defined in this class of extensions of the Standard Model. Finally, we perform a combined fit of the Unitarity Triangle and of new physics contributions in Minimal Flavour Violation, reaching a sensitivity to a new physics scale of about 5 TeV. We also extrapolate all these analyses into a "year 2010" scenario for experimental and theoretical inputs in the flavour sector. All the results presented in this paper are also available at the URL http://www.utfit.org, where they are continuously updated.Comment: 29 pages, 56 figure

Investigating The Physics Case of Running a B-Factory at the Y(5S) Resonance

We discuss the physics case of a high luminosity B-Factory running at the Y(5S) resonance. We show that the coherence of the B meson pairs is preserved at this resonance, and that Bs can be well distinguished from Bd and charged B mesons. These facts allow to cover the physics program of a traditional B-Factory and, at the same time, to perform complementary measurements which are not accessible at the Y(4S). In particular we show how, despite the experimental limitations in performing time-dependent measurements of Bs decays, the same experimental information can be extracted, in several cases, from the determination of time-integrated observables. In addition, a few examples of the potentiality in measuring rare Bs decays are given. Finally, we discuss how the study of Bs meson will improve the constraints on New Physics parameters in the Bs sector, in the context of the generalized Unitarity Triangle analysis.Comment: 47 pages, 22 figure

2000 CKM-Triangle Analysis A Critical Review with Updated Experimental Inputs and Theoretical Parameters

Within the Standard Model, a review of the current determination of the sides and angles of the CKM unitarity triangle is presented, using experimental constraints from the measurements of |\epsilon_K|, |V_{ub}/V_{cb}|, \Delta m_d and from the limit on \Delta m_s, available in September 2000. Results from the experimental search for {B}^0_s-\bar{B}^0_s oscillations are introduced in the present analysis using the likelihood. Special attention is devoted to the determination of the theoretical uncertainties. The purpose of the analysis is to infer regions where the parameters of interest lie with given probabilities. The BaBar "95 %, C.L. scanning" method is also commented.Comment: 44 pages (revised version

Factorization fits to charmless strangeless B decays

We present fits to charmless strangeless hadronic B decay data for mean branching ratios and CP-violating asymmetries using the QCD factorization model of Beneke et al. Apart from one CP-violating parameter, the model gives a very good representation of 26 measured data. We find the CKM angle alpha = (93.5 +/- 8.4 -1.3) degrees and to be quite stable to plausible "charming penguin" corrections.Comment: 4 pages, LaTeX, Minor changes to text, references adde

Supersymmetric contributions to B -> D K and the determination of angle \gamma

We analyze supersymmetric contributions to B^- -> D^0 K^- and B^- ->\bar{D}^0 K^- processes. We investigate the possibility that supersymmetric CP violating phases can affect our determination for the angle \gamma in the unitary triangle of Cabibbo-Kobayashi-Maskaw mixing matrix. We calculate the gluino and chargino contributions to b--> u(\bar{c}s) and b-->c(\bar{u}s) transitions in a model independent way by using the mass insertion approximation method. We also revise the D^0 - \bar{D}^0 mixing constraints on the mass insertions between the first and second generations of the up sector. We emphasize that in case of negligible D^0 -\bar{D}^0 mixing, one should consider simultaneous contributions from more than one mass insertion in order to be able to obtain the CP asymmetries of these processes within their 1\sigma experimental range. However, with a large D^0-\bar{D}^0 mixing, one finds a significant deviation between the two asymmetries and it becomes natural to have them of order the central values of their experimental measurements.Comment: 20 page

Remarks on the hadronic matrix elements relevant to the SUSY K-Kbar mixing amplitude

We compute the 1-loop chiral corrections to the bag parameters which are needed for the discussion of the SUSY K-Kbar mixing problem in both finite and infinite volume. We then show how the bag parameters can be combined among themselves and with some auxiliary quantities and thus sensibly reduce the systematic errors due to chiral extrapolations as well as those due to finite volume artefacts present in the results obtained from lattice QCD. We also show that in some cases these advantages remain as such even after including the 2-loop chiral corrections. Similar discussion is also made for the K --> pi electro-weak penguin operators.Comment: 13 pages, 3 figures [added 1 reference and a discussion about the impact of the NNLO chiral corrections to the "golden ratios" (c.f. Sec.6)

Improved Determination of the CKM Angle alpha from B to pi pi decays

Motivated by a recent paper that compares the results of the analysis of the CKM angle alpha in the frequentist and in the Bayesian approaches, we have reconsidered the information on the hadronic amplitudes, which helps constraining the value of alpha in the Standard Model. We find that the Bayesian method gives consistent results irrespective of the parametrisation of the hadronic amplitudes and that the results of the frequentist and Bayesian approaches are equivalent when comparing meaningful probability ranges or confidence levels. We also find that from B to pi pi decays alone the 95% probability region for alpha is the interval [80^o,170^o], well consistent with recent analyses of the unitarity triangle where, by using all the available experimental and theoretical information, one gets alpha = (93 +- 4)^o. Last but not least, by using simple arguments on the hadronic matrix elements, we show that the unphysical region alpha ~ 0, present in several experimental analyses, can be eliminated.Comment: 16 pages, 7 figure