Measurements of D0-D0bar Mixing and Searches for CP Violation: HFAG Combination of all Data
A. J. Schwartz
备注：
8 pages, 5 figures, 4 tables, presented at the BES-Belle-CLEO-Babar Joint Workshop on Charm Physics, November 26-27, 2007 in Beijing China. To appear in Chinese Physics C (HEP & NP). v2: typo corrected
We present world average values for D0-D0bar mixing parameters x and y, CP violation parameters |q/p| and Arg(q/p), and strong phase differences δand δ_{Kππ}. These values are calculated by the Heavy Flavor Averaging Group (HFAG) by performing a global fit to relevant experimental measurements. The results for x and y differ significantly from zero and are inconsistent with no mixing at the level of 6.7 sigma. The results for |q/p| and Arg(q/p) are consistent with no CP violation. The strong phase difference δis less than 45 degrees at 95% C.L.
Current HFAG averages of the mixing and CP violation parameters in the $D^0$ meson system is to be reviewed. We present recent Belle measurements of the mixing parameters $x$ and $y$ using $D^0\rightarrow K^0_Sπ^+π^-$, and $y_{CP}$ and $A_Γ$ from $D^0\rightarrow h^+h^-$, $D^0\rightarrow K^-π^+$, where $h$ denotes $K$ or $π$. Belle measurements of direct CP violation in $D^+\rightarrow K^0_Sπ^+$, $D^0\rightarrow h^+h^-$, and $D^+\rightarrow K^0_SK^+$ decays together with $ΔA^{hh}_{CP}$ are to be presented.
We present the most recent set of world averages for D0-D0bar mixing and CP violation parameters, as obtained by the Heavy Flavor Averaging Group from a global fit to various measurements. The values obtained for the mixing parameters when allowing for CP violation are x= (0.98 +0.24 -0.26)% and y= (0.83 +-0.16)%; the significance of mixing is 10.2 sigma. There is no evidence for CP violation at the current level of sensitivity.
The current status of the search for indirect CP violation in the neutral D meson system at the B-factories and at LHCb is reported. The indirect CP asymmetry search is performed by the measurement of the proper-time asymmetry ($A_Γ$) in decays of $D^0-\bar{D^0}$ mesons to CP eigenstates, $K^-K^+$ and $π^- π^+$, and by $y_{CP}$, the ratio between the effective lifetime measured in decay to a CP eigenstate and that to the mixed eigenstate $K π$. All results are consistent with the no CP violation hypothesis. The latest world averages for mixing and CP asymmetry in the charm sector evaluated by …
I present here the HFAG averages for the parameters that regulate flavor mixing and \CP violation in the neutral $D$ meson system. I also discuss recent results from the $B$ factories for the measurements of the mixing parameter \yCP and the \CP violation parameter \deltaY (\AGamma) in the lifetime ratio analysis of the transitions to the \CP-even eigenstates $\Dz\to K^+K^-,π^+π^-$, relative to the transitions to the \CP-mixed state $\Dz \to K^-π^+$.
The extraction of charm mixing and CP violation parameters requires the combination of many measurements. The latest averages are reviewed and the contribution of individual measurements is discussed. While it is established that the CP-even eigenstate is the shorter lived, the oscillation frequency of charm mesons is still not known to high accuracy. All CP asymmetries are found to be compatible with zero within less than 3 sigma.
This article reports world averages for measurements on b-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the available results as of winter 2005 conferences. In the averaging, the input parameters used in the various analyses are adjusted (rescaled) to common values, and all known correlations are taken into account. The averages include lifetimes, neutral meson mixing parameters, semileptonic decay parameters, rare decay branching fractions, and CP violation measurements.
This article reports world averages for measurements on b-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the available results as of summer 2004 conferences. In the averaging, the input parameters used in the various analyses are adjusted (rescaled) to common values, and all known correlations are taken into account. The averages include b-hadron lifetimes, B-oscillation (mixing) parameters, semileptonic decay parameters, rare decay branching fractions, and CP violation measurements.
I present here the most recent experimental results in the search for Lepton Flavor and Lepton Number Violating decays of charged leptons, and the perspectives in this field for the next future.
Model-independent techniques for CP violation searches in multi-body charm decays are discussed. Examples of recent analyses from BaBar and LHCb are used to illustrate the experimental challenges involved.
A review of the experimental status in searches for charged Lepton Flavor Violation (LFV) is presented. Searches for LFV in decays of leptons, heavy mesons, and bosons are explored, with an emphasis on the experiments providing the best constraints in each sector. In addition, prospects for upper limits by current and upcoming experiments in the next decade are discussed.
LHCb has collected the world's largest sample of charmed hadrons. This sample is used to search for direct and indirect CP Violation in charm. Recent and updated measurements from several decay modes are presented.
Supersymmetric particles that are long-lived or violate R-parity could evade many conventional searches for supersymmetry. This talk presents the latest results of searches for supersymmetry with long-lived particles or R-parity violation performed by the ATLAS and CMS collaborations using $\sim$20 fb$^{-1}$ of proton-proton collisions at center-of-mass energy of 8 TeV delivered by the LHC.
We review searches for mixing and CP violation in the D0-D0bar system and discuss the first evidence for mixing recently obtained by the Belle and BABAR collaborations. We also present world average values for the mixing parameters x=Delta m/Gamma and y=Delta Gamma/(2 Gamma) as calculated by the Heavy Flavors Averaging Group.
The first description of the experimental program "OKA" with RF-separated K+/- beam at Protvino U-70 PS is presented. The parameters of the beam as well as the potential for CP-violation searches are discussed.
Recent hints for lepton-universality violation in $b\to c\ellν$ and $b\to s\ell\ell$ transitions could imply the existence of lepton-flavour violating $b$ decays. The LHCb experiment is well suited for the search for these decays due to its large acceptance and trigger efficiency, as well as its excellent invariant mass resolution and particle identification capabilities. Recent results on searches for lepton-flavour violating decays from the LHCb experiment are presented.
Searches for lepton flavour and lepton number violation in kaon decays by the NA48/2 and NA62 experiments at CERN are presented. A new measurement of the helicity suppressed ratio of charged kaon leptonic decay rates $RK=BR(Ke2)/BR(Kmu2) to sub-percent relative precision is discussed. An improved upper limit on the lepton number violating K+- --> pi-+mu+-mu+- decay rate is also presented.
In the Standard Model of particle physics, lepton flavour and lepton number are conserved quantities although no fundamental symmetry demands their conservation. I present recent results of searches for lepton flavour and lepton number violating hadron decays measured at the B factories and LHCb. In addition, the LHCb collaboration has recently performed a search for the lepton flavour violating decay τ^- \to μ^-μ^-μ^+. The obtained upper exclusion limit, that has been presented in this talk for the first time, is of the same order of magnitude as those observed at the B factories. This is the…
Recent Kaon decay studies seeking lepton-flavor violating (LFV) new-physics effects are briefly discussed. The main focus is set on precise measurements of rare or not-so-rare decays aiming at finding evidence of deviations from the SM prediction rather than on the results from direct searches of LFV transitions forbidden or ultra-rare in the SM.
In the Standard Model \CP violation in charm decays is expected to be very small, at the level of 0.1% or less. A significant excess of \CP violation with respect to the Standard Model predictions would be a signature of new physics. We report on recent searches for \CP violation in charm meson decays at \babar, using a data sample corresponding to an integrated luminosity of about 470 \invfb. In particular, we report on searches for \CPV in the 3-body $\Dp\to\Kp\Km\pip$ decay and for decay modes with a \KS in the final state, such as $\Dp\to\KS\Kp$, $\Ds\to\KS\Kp$, $\Ds\to\KS\pip$. A lifetime…
Results of recent searches for new physics in CP violation in charm decays from the BABAR experiment are presented. These results include a measurement of $D^0$ - $\bar{D}^0$ mixing and searches for CP violation in two-body $D^0$ decays, a search for CP violation in the charm decays $D^{\pm} \to K^0_S K^{\pm}$ and $D^{\pm}_s \to K^0_S K^{\pm}$, $K^0_S π^{\pm}$, and a search for direct CP violation in the singly-Cabibbo suppressed $D^{\pm} \to K^+ K^- π^{\pm}$ decays. These studies are based on the final dataset collected by BABAR at the PEP-II B factory at SLAC in the period 1999-2008. No evid…
Using data collected with the BaBar detector at PEP-II at SLAC, we report on several tau lepton measurements that are used to determine the modulus of the Cabibbo-Kobayashi-Maskawa matrix element Vus, and to check the Standard Model predictions of lepton universality and CPT conservation.
Searches for lepton-flavor-violating decay of a tau lepton to a lighter mass lepton and a photon have been performed with the entire dataset of (963 +- 7) x 10^6 tau decays collected by the BaBar detector near the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of BR(tau -> e gamma) < 3.3 x 10^-8 and BR(tau -> mu gamma) < 4.4 x 10^-8 at 90% confidence level.
We describe measurements of CP and CPT violation parameters in B^0B^0bar oscillations, performed at BaBar by using BBbar events collected at the Y(4S) mass peak. These are obtained from two different B-reconstruction methods, namely: searching for two inclusive semileptonic B^0 decays in an event or partially reconstructing one of the B^0 mesons in the D* l nu_l channel. The results are in agreement with one another and with the most recent theoretical calculations in the Standard Model scenario.
I review recent results from experiments on rare decays of kaons, concentrating on searches for lepton flavor violation (LFV) and on measurements of quark mixing (CKM) matrix elements. The LFV results are the culmination of 15 years of experimentation at Brookhaven National Laboratory and are unlikely to be improved upon soon. The CKM studies derive from measurements of decay rates of charged and neutral kaons into lepton anti-lepton pairs, both with and without a charged or neutral pion. I discuss recent results and prospects for improved measurements that could provide an unambiguous test of…
This article reports world averages for measurements of b-hadron and c-hadron properties obtained by the Heavy Flavor Averaging Group (HFAG) using the results available at the end of 2007. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, and parameters of semileptonic decays.
LHCb has started its charm physics programme using the data taken at the LHC. The first measurements of open charm production cross-sections for proton proton collisions at $\sqrt{s}=7 \tev$ are presented. The cross-sections of the \PDzero, $\PDstar^+$, \PDplus, and \PDsplus mesons are found to be in broad agreement with theory predictions. The prospects for measurements of charm mixing, CP and T violation in decays of neutral \PD mesons at LHCb are discussed. Furthermore, plans for CP violation measurements using charged \PD mesons are presented. Most analyses are expected to yield results im…
This study presents comparative CP sensitivities for various sets of water Cerenkov and liquid argon detectors combined with various running scenarios associated with DAEdALUS and LBNE neutrino beams at DUSEL. LBNE-only running scenarios show fairly small differences in sensitivity for the various detector combinations. On the other hand, the DAEdALUS-only and DAEdALUS-plus-LBNE running gives significantly better sensitivity for a detector combination that includes at least 200 kt of Gd-doped water Cerenkov detector, exceeding the sensitivity of a Project-X 10 year run. A 300 kt Gd-doped water…
The BaBar experiment has recently obtained some important results in the search for new physics in leptonic and lepton flavor violating decays, exploiting the complete datasets collected at the $Υ(4S)$, $Υ(3S)$ and $Υ(2S)$ energies. In particular, new limits on the ratio $Γ(Υ(1S)\toτ^+τ^-)/Γ(Υ(1S)\toμ^+μ^-)$, on lepton flavor violating decays of the $Υ(3S)$ and $Υ(2S)$, and on $τ$ decays to three charged leptons or $τ\to e/μγ$ are presented.
Searches for experimental manifestations of CP violation have born much fruit in recent years with the discovery of direct CP violation and the first evidence of CP violation outside of the neutral kaon system. Nevertheless we still know little about CP violation: its origin remains a mystery and there is little hard evidence that it is the sole province of the standard model. Searches for CP violation in hyperon decays offer promising possibilities as they are sensitive to certain beyond-the-standard-model sources that are not probed in other systems. We report on the status of such searches,…
The CDF experiment at the Tevatron $p\bar{p}$ collider has pioneered and established the role of hadron collisions in exploring flavor physics through a broad program that is now at its full maturity. We report new results sensitive to physics beyond the standard model, obtained using the whole CDF data set; including new bounds on the \Bs\ mixing phase and the decay width difference of \Bs\ mass-eigenstates and a measurement of the difference of CP asymmetries in $K^+K^-$ and $π^+π^-$ decays of $D^0$ mesons. We also present a new measurement of the $\Bs \rightarrow D^{(*)+}_s D^{(*)-}_s$ bran…
A search for the lepton number violating $K^{+}\rightarrowπ^{-}μ^{+}e^{+}$ and lepton flavour violating $K^{+}\rightarrowπ^{+}μ^{-}e^{+}$ decays is reported using NA62 data collected in 2017 and 2018. No significant excess is observed above the background expectation and therefore upper limits are established on the branching ratios at $90\%$ confidence level: $\mathcal{B}(K^{+}\rightarrowπ^{-}μ^{+}e^{+})<4.2\times10^{-11}$ and $\mathcal{B}(K^{+}\rightarrowπ^{+}μ^{-}e^{+})<6.6\times10^{-11}$. These results improve over the previous limits by factors of $12$ and $8$ respectively.
Recent CLEO results on neutral charm meson decays presented at the XXXVIth Rencontres de Moriond are discussed. We find no evidence of CP asymmetry in five different two-body decay modes of the D0 to pairs of light pseudo-scalar mesons. We present a measurement of the mixing parameter y_CP = -0.011 +- 0.025 +- 0.014 by searching for a lifetime difference between the CP neutral K+ pi- final state and the CP even K+ K- and pi+ pi- final states. Finally, we describe the first measurement of the rate of wrong-sign D0 to K+ pi- pi0 decay: R_WS = (0.43 +0.11 -0.10 +- 0.07)%.
A summary of the recent searches for anomalous single top-quark production and lepton flavour violation in high energy ep collisions is presented. Single top-quark production via an anomalous flavour changing neutral current gamma-u-t coupling would lead to the reaction ep->etX, t->Wb. H1 observed an excess of events above the Standard Model prediction in the leptonic decay channel of the W boson, leading to an isolated lepton, large missing transverse momentum and a jet with large transverse momentum. Five of these events are compatible with single top-quark production, compared to 1.8 events…
We search for direct CP violation in charmless hadronic B decays observed in a sample of about 22.7 million $B\bar{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^+e^-$ collider. We measure the following charge asymmetries: ${\cal A}_{CP} (B^{\pm}\toη^\prime K^{\pm}) = -0.11\pm 0.11\pm 0.02$, ${\cal A}_{CP} (B^{\pm}\toωπ^{\pm}) = -0.01^{+0.29}_{-0.31}\pm 0.03$, ${\cal A}_{CP} (B^{\pm}\toϕK^{\pm}) = -0.05\pm 0.20\pm 0.03$, ${\cal A}_{CP} (B^{\pm}\toϕK^{*\pm}) = -0.43^{+0.36}_{-0.30}\pm 0.06$, and ${\cal A}_{CP} (B^{0}\toϕK^{*0}) = 0.00\pm 0.27\pm 0.03$.
The BaBar experiment recorded 471 x 10^6 BBbar pairs at the Y(4S) resonance (corresponding to an integrated luminosity of 429 fb^-1). We present here a selection of recent results from the BaBar collaboration: search for lepton-number violation in the decay B^+ -> h^- l^+ l^+, search for lepton-flavor violation in B^+/- -> h^+/- tau l and CP-violation in tau^- -> pi^- KS (>= 0 pi^0) nu_tau.
We review results from searches for mixing and CP violation in the D0-D0bar system. No evidence for mixing or CP violation is found, and limits are set for the mixing parameters x, y, x', y', and several CP-violating parameters.
The NA48/2 experiment at CERN collected a large sample of charged kaon decays to final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay $K^{\pm}\toπ^{\mp}μ^{\pm}μ^{\pm}$ is reported: $\mathcal{B}(K^{\pm}\toπ^{\mp}μ^{\pm}μ^{\pm})<8.6 \times 10^{-11}$ at 90% CL. Searches for two-body resonances $X$ in $K^{\pm}\toπμμ$ decays (such as heavy neutral leptons $N_4$ and inflatons $χ$) are also presented. In the absence of signals, upper limits are set on the products of branching fractions $\mathcal{B}(K^{\pm}\toμ^{\pm}N_4)\mathca…
Results on CP violation searches in charm decays performed by the LHCb experiment are reviewed. These include an update of the measurement of the difference in time-integrated {\em CP} asymmetry between $D^0\to K^-K^+$ and $D^0\to π^-π^+$ using $D^0$ from prompt $D^{*+}, a measurement of the same observable using an independent sample of $D^0$ from semileptonic B decays, and CP violation searches performed on charged $D$ mesons. All results have been released since FPCP 2012.
The NA48/2 experiment at CERN collected a large sample of charged kaon decays into final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay $K^{\pm}\toπ^{\mp}μ^{\pm}μ^{\pm}$ obtained from this sample is reported: $\mathcal{B}(K^{\pm}\toπ^{\mp}μ^{\pm}μ^{\pm})<8.6 \times 10^{-11}$ at 90\% CL. Searches for two-body resonances in the $K^{\pm}\toπμμ$ decays (including heavy neutral leptons~$N_4$ and inflatons~$χ$) in the accessible range of masses and lifetimes are also presented. In the absence of a signal, upper limits are set …
In e+e- collisions recorded using the CLEO II.V detector we have studied the Cabibbo suppressed decay of D0 -> pi+pi-pi0 with the initial flavor of the D0 tagged by the decay D*+ -> D0pi+. We use the Dalitz-plot analysis technique to measure the resonant substructure in this final state and observe ρπand non-resonant contributions by fitting for their amplitudes and relative phases. We describe the pipi S-wave with a K-matrix formalism and limit this contribution to the rate to be < 2.5% @95% confidence level, in contrast to the large rate observed in D+ -> pi+pi-pi+ decay. Using the amplitude…
The NA48/2 experiment at CERN collected a large sample of charged kaon decays into final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay $K^{\pm} \to π^{\mp} μ^{\pm} μ^{\pm}$ obtained from this sample is reported: $\mathcal{B}(K^{\pm} \to π^{\mp} μ^{\pm} μ^{\pm})<8.6 \times 10^{-11}$ at 90\% CL. Searches for two-body resonances in the $K^{\pm} \to πμμ$ decays (including heavy neutral leptons~$N_4$ and inflatons~$χ$) in the accessible range of masses and lifetimes are also presented. In the absence of a signal, upper limit…
Recent results on searches for physics beyond the Standard Model obtained by the H1 and ZEUS experiments are reported here. After a brief introduction to the HERA collider, indirect searches for contact interactions and extra-dimensions are presented as well as direct searches for new physics including leptoquarks, lepton-flavour violation, squarks produced by R-parity violation and excited fermions. New results from isolated lepton events and single top searches are also presented. Finally the future prospects of HERA-2 are shown.
The LHCb experiment recorded data corresponding to an integrated luminosity of 3.0 $fb^{-1}$ during its first run of data taking. These data yield the largest samples of charmed hadrons in the world and are used to search for CP violation in the $D^0$ system. Among the many measurements performed at LHCb, a measurement of the direct CP asymmetry in $D^0 \rightarrow K_S^0 K_S^0$ decays is presented and is found to be $A_{CP}(D^0 \rightarrow K_S^0 K_S^0) = (-2.9 \pm 5.2 \pm 2.2)\, \%, $ where the first uncertainty is statistical and the second systematic. This represents a significant improvemen…
Searches for lepton flavor violation in tau decays are unambiguous signatures of new physics. The branching ratios of tau leptons at the level of 10^-10 - 10^-9 can be probed with 50 ab^-1 of electron-positron annihilation data being collected by the Belle II experiment at the world's highest luminosity accelerator, the SuperKEKB, located at the High Energy Accelerator Research Organization, KEK, in Tsukuba, Japan. Searches with such expected sensitivity will either discover new physics or strongly constrain several new physics models.
We study the complementary tests of lepton number violation in $0νββ$-decay experiments, long-lived particle (LLP) searches at the LHC main detectors ATLAS/CMS, and a proposed far detector MATHUSLA. In the context of a simplified model with a scalar doublet $S$ and a Majorana fermion $F$, we show that while the $0νββ$-decay experiments can probe a larger portion of parameter space, the LLP searches can uniquely probe the region of smaller couplings and masses if $S$ is at TeV scale while $F$ is at or below the electroweak scale. We also investigate constraints on the parameter space from the e…
Studies of charm physics with the 2010 LHCb data sample are presented. Time-integrated searches for CP violation in D+ -> K- K+ pi+ and D0 -> K- K+, pi- pi+ are discussed.
Techniques for performing model-independent searches for direct CP violation in three and four-body decays are discussed. Comments on the performance and the optimisation of a binned chisquare approach and an unbinned approach, known as the energy test, are made. The use of the energy test in the presence of background is also studied. The selection and treatment of the coordinates used to describe the phase-space of the decay are discussed. The conventional model-independent techniques, which test for P-even CP violation, are modified to create a new approach for testing for P-odd CP violatio…
This paper presents the final interpretation of the results from DELPHI on the searches for Higgs bosons in the Minimal Supersymmetric extension of the Standard Model (MSSM). A few representative scenarios are considered, that include CP conservation and explicit CP violation in the Higgs sector. The experimental results encompass the searches for neutral Higgs bosons at LEP1 and LEP2 in final states as expected in the MSSM, as well as LEP2 searches for charged Higgs bosons and for neutral Higgs bosons decaying into hadrons independent of the quark flavour. The data reveal no significant exces…
