Flavor Physics

The following sections are included:

• PREFACE

• CONTENTS

After 36 years there exist only two numbers that measure CP violation: β and ∈' . A third sin 2β has preliminary values presented at this conference…

We discuss precision tests of the standard model in radiative and semileptonic rare B-decays and CP-violating asymmetries, and possible signatures of supersymmetry in these processes. Motivated by current data, and with an eye on the forthcoming measurements, we restrict ourselves to the processes in which the bench marks set by the standard model have either been met by ongoing experiments or are expected to be met shortly. This includes the mixing-induced CP asymmetry, measured through sin 2β, and branching ratios for the radiative and semileptonic rare decays B → X_sγ, B → K*γ, B → X_sℓ⁺ℓ⁻ and B → (K,K*)ℓ⁺ℓ⁻, where ℓ^± = e^±, μ^±.

Forward/Backward asymmetry of events provides the most precise measurement of at LEP I. In this note we will review :

• The different techniques used to measure .

• The recent improvements implemented by the LEP experiments in their analysis.

• The corrections applied to to extract .

The value obtained for from is in favour of a high value for the Higgs mass compared to what is obtained with other observables like A_LR or m_W. This difference is commented.

We review of the various low energy mechanisms of CP violation with emphasis on the relationship with the flavor physics. More space is devoted to the recently popular new sources of CP violating sources in minimal supersymmetric theories and discuss their related interesting phenomenology.

We have systematically investigated the semi-inclusive B decays B → MX, which are manifestations of the quark decay b → Mq, within a framework inspired by QCD-improved factorization. These decays are theoretically clean and have distinctive experimental signatures. We focus on a class of these that do not require any form factor information and therefore may be especially suitable for extracting information on the angles α and γ of the unitarity triangle. The strong phase coming from final-state rescattering due to hard gluon exchange between the final states can induce large rate asymmetries for tree-dominated color-suppressed modes . The nonfactorizable hard spectator interactions in the 3-body decay , though phase-space suppressed, are extremely important for the tree-dominated modes , φX, J/ψX_s, J/ψX and the penguin-dominated mode . Our result for is in agreement with experiment. , , and B⁻ → (K⁰X_s, K^*0X_s) are the most promising ones in searching for direct CP violation: they have branching ratios of order 10⁻⁶ – 10⁻⁴ and CP rate asymmetries of order (10 – 40)%.

Recent CLEO results on beauty and charm meson decays presented at the International Conference on Flavor Physics (ICFP2001) are discussed. The results include exclusive rare B decays (B → PP, PV, VV, φK^(*), l⁺l⁻K^(*)), inclusive b → sγ, and CP violation measurements in beauty and charm mesons. Preliminary results on rare B decays using CLEO III data are also included.

The current status of the direct-CP violation, ɛ′/ɛ measurement from the Fermilab KTeV experiment is reviewed here. The long-sought “direct-CP violation” effect in the two-pion system of neutral kaon decays has clearly been observed in the KTeV data. A preliminary measurement of the CP-violating charge asymmetry δ_L is also reported here for the mode K_L → π^±e^∓ν based on 298 million analyzed decays. The measurement is a substantial improvement on the current world average. A value of δ_L = 3322 ± 58(stat) ± 47(sys) ppm is measured and is in good agreement with previous measurements. The result can be used to place more stringent limits on CPT and ΔS = ΔQ violation in the neutral kaon system.

A pedestrian review of the recent spectacular discovery of the vacuum energy or the dark energy in the Universe is presented with emphasis on its impact on the cosmology.

Double beta decay is indispensable to solve the question of the neutrino mass matrix together with ν oscillation experiments. Recent analysis of the most sensitive experiment since eight years - the HEIDELBERG-MOSCOW experiment in Gran-Sasso - yields evidence for the neutrinoless decay mode. This result is the first evidence for lepton number violation and proves the neutrino to be a Majorana particle. We give the present status of the analysis in these Proceedings. It excludes several of the neutrino mass scenarios allowed from present neutrino oscillation experiments - essentially only degenerate and partially degenerate mass scenarios survive. This result allows neutrinos to still play an important role as dark matter in the Universe. To improve the present result, considerably enlarged experiments are required, such as GENIUS. A GENIUS Test Facility has just been funded and will come into operation by end of 2002.

A new and precise measurement of the parameter of direct CP violation Re(ɛ′ /ɛ) has been determined by the NA48 experiment at the CERN SPS from the decay rates of neutral kaons into two pions. With seven times the previous statistics the combined result Re(ɛ′/ɛ) = (15.3 ± 2.6) × 10⁻⁴ clearly establishes direct CP-violation with 5.9 standard deviations significance.

Over the past few years the experiments at Fermilab have continued their tradition of important measurements in charm and beauty physics. The great diversity of these measurements makes it impossible to do justice to them all in this report. Instead a few of them will be discussed in some detail, including mixing, doubly Cabibbo suppressed decays and the study of the Dalitz plots of three-body charm decay. The report will continue with a survey of the b physics results from Run I of the Tevatron collider and will conclude with a discussion of the prospects for b and c physics at the Tevatron collider during Run II and beyond.

The characteristics and phenomenology of neutrino oscillation in extra dimensions are briefly reviewed

An effective chiral theory of pseudoscalars, vectors, and axial-vectors is presented. In this theory mesons are coupled to quarks. At quark level mesons have no kinetic terms which are generated by quark loops. The theory has both explicit chiral symmetry(in the limit, m_q → 0) and dynamical chiral symmetry breaking. Large N_C expansion is a natural result. Tree diagrams are at leading order and meson loops are at higher orders. In this theory octet pseudoscalars are Goldstone bosons. Masses and decay widths of the mesons agree with data. VMD, Wess-Zumino-Witten anomaly, and OZI rule are obtained. Besides three current quark masses there are other two parameters: a universal coupling constant and a cutoff. At low energy the theory goes back to ChPT. The phenomenology of the theory is successful.

We present results from BABAR experiment for the measurement of inclusive and exclusive branching fractions of B mesons into final states containing J/ψ, ψ(2S) and χc. The contributions of CP even and odd amplitudes in the decay B⁰ → J/ψK^*0 are determined from an angular analysis. We report the measurements of the branching ratios B⁰ → D^*+D^*− and , and the study of exclusive two-body and quasi-two-body charmless decays. The branching fraction of the decay B⁰ → K^*0γ has been determined and the corresponding CP asymmetry has been measured.

We review the current status of theoretical study of non-leptonic two body B decays. There are two independent directions for this purpose. One is the so called QCD factorization approach (or BBNS approach), which is based on naive factorization approach. The other one is named perturbative QCD approach. We list the different ideas and applications of the two method, and make a comparison between the two.

During its first year of operation at the PEP-II asymmetric B factory at SLAC, the BABAR detector has collected 23 millions of pairs. The study of the time-dependent CP-violating asymmetry in neutral B decays to , and is presented here. The amplitude of the asymmetry is measured to be: sin2β = 0.34 7 ± 0.20(stat) ± 0.05(syst). Results on B lifetimes and oscillations are also reported.

We discuss a measurement of the Standard Model CP violation parameter, sin2φ₁, based on a data sample of 31.3×10⁶ pairs, accumulated at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e⁺e⁻ collider. One neutral B meson is reconstructed in the J/ψK_S, ψ(2S)K_S, χ_c1K_S, η_cK_S, J/ψK_L or J/ψK^*0 decay channel and the flavor of the accompanying B meson is identified from its particle decay products. From the asymmetry in the distribution of the time intervals between the two B-meson decay points, we determine sin2φ₁=0.99±0.14(stat)±0.06(syst), which shows the observation of large CP violation in the B⁰ meson system. The current status of the KEKB collider and the Belle detector is also described.

I discuss CP violation in Λ → pπ⁻ contrasting the standard model expectations with upper bounds that can be saturated in new physics scenarios. I review recent progress in the theoretical estimates.

The theoretical status of direct CP violation ɛ′/ɛ is briefly reviewed. Special attention is paid to the recent new consistent predictions for both the ratio ɛ′/ɛ and the ΔI = 1/2 rule within the standard model. In particular, two matching conditions resulting from the matching between the QCD and chiral perturbation theory(ChPT), and also some algebraic relations of chiral operators are found to be very useful. It is of interest that the new predictions are no longer sensitive to the strange quark mass, and are also renormalization scale and scheme independent in the leading QCD and chiral loop approximation with large N_c approach. The new prediction for the direct CP violation with the value ɛ′/ɛ = (20 ± 4) × 10⁻⁴[Imλ_t/1.2 × 10⁻⁴] is consistent with the most recent experimental results reported by the NA48 and KTeV groups.

In this talk, I will discuss possible new physics effects that modify the interaction of Higgs boson(s) with top and bottom quarks, and discuss how to detect such effects in current and future high energy colliders.

We present a mixing search in hadronic decays at the Belle experiment, measuring the “wrong-sign” / “right-sign” ratio (r_WS) in the decay D⁰ → K^± π^∓. Using 10 fb⁻¹ of e⁺e⁻ collision data collected by the Belle detector during its first six months of data taking, we obtain a preliminary result of r_WS = (0.30 ± 0.06 ± 0.08)%. We also report a y_CP measurement at Belle, based on the lifetime difference of the D⁰ → Kπ and D⁰ → KK decays.

Motivated by the recent measurement on the anomalous magnetic moment¹ (a_μ) and the proposed dedicated experiment on the electric dipole moment ² (d_μ) of the muon at BNL, we review various theoretical predictions on d_μ. In particular, we discuss the possibility of having a large value of d_μ in the left-right symmetric model, while explaining the data on a_μ.

The NA48 experiment, designed to measure with great accuracy the direct CP violation in K_L,S → ππ decays, is also exploiting the high intensity of its beams to detect a wide range of neutral kaon and hyperon decays. The most recent results, as well as the future experimental program on rare decays, are presented.

We review the important two-loop contribution to the electric dipole moment (EDM) of the electron by the CP violating Higgs boson in models beyond the standard model. The two-loop mechanism is then extended to the precision measurement of the CP conserving g_μ − 2 due to a rather light pseudoscalar boson. The current result of the g − 2 experiment prefers a pseudoscalar boson lighter that 100 GeV

The results of the LEP, SLD and CDF experiments will be reviewed. No evidence for oscillations has been found and a limit on the mass difference between the two physical B_s states is put: Δm_s is larger than 15 ps⁻¹ at 95% CL. The sensitivity of the experiments is 18.1 ps⁻¹.

I report our recent works on the effects of CP violating phases in SUSY models on B and K phenomenology.

The mean charge sum rule for the light sea quarks in the nucleon which holds under the same theoretical footing as the modified Gottfried sum rule shows that a usual parameterization of the strange sea quark distribution underestimate its contribution in the small x region. We give a discussion of the soft pion contribution at high energy as a possible explanation of the saturation of the sum rule and show that it naturally explains why the strange sea quark is suppressed in the region above x ∼ 0.01 while it becomes abundant below it.

We give a review of the theoretical status of the lifetime predictions in the standard model. In case of (ΔΓ/Γ)_Bs we are already in a rather advanced stage. We obtain . It seems to be difficult to improve these errors substantially. In addition now some experimental results are available. For τ_B+/τ_Bd and τ_Λb/τ_Bd the theoretical status is much less advanced and the discrepancy between experiment and theory still remains. We conclude with a what-to-do-list for theorists.

It is shown that compared to that of SM, the branching ratio of B → ℓ⁺ℓ⁻ can be enhanced by an order of magnitude in a model II 2HDM. In SUSY model it can be enhanced by three order of magnitude and even reach the experimental bounds. violation of this process is shown to be even as large as 40% for B_d in very large range of parameter space. For B_s it can be as large as 3%. The SM prediction is and for B_d and B_s respectively

In this talk I briefly review the status of Charmonium production in photon-photon collisions. I would like to mention that although the preliminary data were obtained in experiment, theoretical calculation is not in a compatible status, that is the result of dominant contributing process is still not available.

We study the effect of large CP violating phases in the effective Supersymmetric theory on the direct CP asymmetry in the decays B → X_dγ and B → X_sγ. With unconstrained Supersymmetric CP violating phases we show that the direct CP asymmetry for b → dγ (b → sγ) lies in the region , where a positive (negative) asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B → X_dγ proves too difficult experimentally, its asymmetry contributes non–negligibly to the measurements of , for B → X_sγ and thus should be included in future analyses.

A new framework of heavy quark effective field theory (HQEFT) is studied and compared with the usual heavy quark effective theory (HQET). |V_ub|, |V_cb| and heavy meson decay constants are extracted in the new framework. HQEFT can yield reasonable results for both exclusive and inclusive decays.

We present the preliminary results of the charmonium decay of B mesons based on data sample of 12.2 fb⁻¹, accumulated at ϒ(4S) resonance with the Belle detector at KEKB collider during Oct. 1999 to Jan. 2001. We have measured the branching fraction for the inclusive and exclusive B decays to modes which include charmonium.

Status of HERA – B, a fixed target experiment at the storage ring HERA at DESY is briefly described and physics goals for the run 2000/2001 are discussed.

The recent data on asymmetry in B → J/φK_S and muon g − 2 are discussed in the framework of standard model and beyond. Possible new phase effects besides the CKM phase are discussed in the processes concerning violation in B decays and muon anomalous magnetic moment (muon g − 2). It is found that the new phases will result in difference between angles β measured from B → J/φK_S and the one from global fit. The ration between them serves as a probe of not only new physics but also new phase besides the CKM phase In the case of muon g − 2, the new phase may change the interferences between various contributions. By including the new phases, some cancelations in the real coupling cases can be avoided and the large value of g − 2 observed in the recent measurements can be understood.

The problem of chirally enhanced corrections for B decays into two light pseu-doscalars in QCD factorization scheme is discussed. We find that the infrared divergences of the vertex corrections cancel only if the twist-3 meson wave functions are symmetric. In that case chirally enhanced corrections can be included consistently. The divergences appeared in the hard spectator scattering are also discussed briefly.

We have analyzed the B → π and B_s → K semileptonic form factors and B → Vγ(V = K*, ρ, ω) processes in the light-cone QCD sum rules. In order to enhance the predictivity and reliability of numerical results the chiral-current correlator is employed and the twist-3 light-cone wavefunction can be effectively eliminated from the sum rules.

I review the known approaches to two-body nonleptonic B meson decays, including factorization assumption, modified factorization assumption, QCD factorization, and perturbative QCD factorization. Important phenomenological aspects of these approaches are emphasized.

We study the tensor form factors for P → P and P → V transitions in the light-front quark model with P and V being pseudoscalar and vector mesons, respectively. We explore the behaviors of these form factors in the entire physical range of 0 ≤ p² ≤ (M_i – M_f)². At the maximum recoil of p² = 0, we compare our results of the form factors in B → K, K* with various other calculations in the literature.

The HQET sum rule analysis for the Λ_b matrix element of the four-quark operator relevant to its lifetime is reported. Our main conclusion is that the lifetime ratio τ(Λ_b)/τ(B⁰) can be as low as 0.91.

The gluon condensates at finite temperature are calculated in the framework of the grand partition function for a weak-interacting instanton medium of a disordered phase. It is found that the temperature behavior of both chromomagnetic and chromoelectric gluon condensates depends sensitively on the flavor number. The more the flavors are, the faster the gluon condensates decrease. In the three-flavor case, the gluon condensates would be vanish (or the scale invarience would be restored) approximately at the temperature of 180MeV.

We study the exclusive decay of 1⁻⁻ heavy quarkonium into one photon and two pions in the kinematic region, where the two-pion system has a invariant mass which is much smaller than the mass of heavy quarkonium. Neglecting effects suppressed by the inverse of the heavy quark mass, the decay amplitude can be factorized, in which the non-perturbative effect related to heavy quarkonium is represented by a non-relativistic QCD matrix element, and that related to the two pions is represented by a distribution amplitude of two gluons in the isoscalar pion pair. Experiment observation of this process can provide information about how gluons are converted into the two pions and may provide an interesting place to study I = 0 s-wave ππ scattering.

In the framework of large extra-dimension models, oscillations between neutrinos on the brane and those in the bulk can be affected by the un-suppressed gravitational interaction. For solar neutrinos, oscillation to sterile states is substantially modified if the size of the extra dimension is of the order of current bounds and the fundamental scale is near the electroweak one. The physics of ultra-high energy neutrinos in cosmic-ray physics is modified even for much larger fundamental scales. These examples are instances of a more general property of fields allowed to propagate in different portions of space-time, for which the reduction to four dimensions leads to an effective violation of the principle of equivalence

In this short report, a brief introduction to Arkani-Hamed, Cohen, Georgi model (ACG-model, (de)constructing dimensions model), whose main characters are that extra-dimensional space-time are generated dynamically from a four-dimensional gauge theory and that extra dimensions are lattices, will be given first. Then after a concise review of NCG on cyclic groups, actions for gauge fields along extra dimensions will be constructed by virtue of NCG and classical (vacuum) solutions will be solved, with low energy phenomenology being classified accordingly. As a conclusion, the behavior of spontaneous symmetry broken within ACG-model can be determined by noncommutative Yang-Mills theory.

The new project GENIUS will cover a wide range of the parameter space of predictions of SUSY for neutralinos as cold dark matter. Further it has the potential to be a real-time detector for low-energy (pp and ⁷Be) solar neutrinos. A GENIUS Test Facility has just been funded and will come into operation by end of 2001.

We study the self-tuning of general brane junctions and brane networks on the 6-dimensional space-time. For the general brane junctions, there may exist one fine-tuning among the brane tensions. For the brane networks, similar to the 5-dimensional self-tuning brane models, the brane tensions can be set arbitrarily and there exists the singularity for the metric and bulk scalar. And if we want to regularize the singularity, we will introduce the fine-tuning among the brane tensions. In addition, because the 4-dimensional cosmological constant we observe may be positive and very small, we discuss the brane network with de Sitter brane intersections by introducing a bulk scalar.

Neutrino oscillation is discussed with emphasis placed more on its quantum-mechanical and kinematic aspects. Treating neutrinos explicitly as wave packets with their momentum distribution functions to have a Gaussian form, we first investigate how neutrinos propagate, without referring to how they are created. We then study the case in which the neutrinos in question are created as a result of two-body decay of pions. We pay particular attention to the questions if and how the standard framework of neutrino oscillation would be modified.

We report on recent results showing that a rich non-perturbative vacuum structure is associated with flavor mixing in Quantum Field Theory. We treat explicitly the case of mixing among three generations of Dirac fermions. Exact oscillation formulas are presented exhibiting new features with respect to the usual ones. CP and T violation are also discussed.

Texture specific mass matrices have been investigated in the context of quark mixing phenomenon. In particular, the implications of texture 4 zero mass matrices have been studied for CKM phenomenology as well as for element U_e3 of the neutrino mixing matrix.

Summary Talk: International Conference of Flavor Physics (ICFP 2001). Zhang–Jia–Jie, Hunan, China (May / June 2001)

The following sections are included:

• Schedule of ICFP2001

• Conference Program

• Photos