We review basic phenomenology on $D^0$ mixing/CP violation and recent experimental results on them. $D^0$ mixing is established by combining results from multiple experiments but no CP violation in the charm sector has been seen. $D^0$ mixing from a single experiment will clarify the size of the mixing, and observation of CP violation in charm decays at the present level of experimental sensitivity would be clear signal of new physics beyond the standard model.
In these proceedings, recent results on time-dependent and time-integrated measurements of $C\!P$ violation and of meson mixing in the charm sector are presented, including the first observation of $C\!P$ violation in the charm system.
This document presents eight recent and new analyses from the LHCb experiment covering results on CKM angle $γ$ and high precision measurements on charm mixing parameters. In addition, the latest CP violation measurements in charm and beauty decays are reported.
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 and to measure $D^0$ mixing parameters. Preliminary measurements from several decay modes are presented, with complementary time-dependent and time-integrated analyses.
LHCb continues to expand its world-leading sample of charmed hadrons collected during LHC's Run 1 (2010-2012) and Run 2 (2015-present). This sample is yielding some of the most stringent tests of the Standard Model understanding of charm physics. This includes precise measurements of the neutral D-meson mixing parameters and some of the most sensitive searches for direct and indirect CP violation in charm interactions.
Precision measurements in charm physics offer a window into a unique sector of potential New Physics interactions. LHCb is poised to become a world leading experiment for charm studies, recording enormous statistics with a detector tailored for flavor physics. This article presents recent charm CPV and mixing studies from LHCb, including LHCb's first CP asymmetry measurement with 37 inverse pb of data collected in 2010. The difference of the CP asymmetries of D0 decays to the K-K+ and π-π+ final states is determined to be ΔA_{CP} = (-0.28 +/- 0.70 +/- 0.25)%. Significant updates to the materia…
Recent measurements of branching fractions and CP-violating partial-rate asymmetries for rare hadronic B-meson decays by the asymmetric-energy B-factory experiments, Belle and BaBar, are reviewed.
This proceeding contribution presents the latest measurement of the CP-violation and other physics parameters in the $B_s^0 \to J/ψϕ$ decay channel performed by the ATLAS, CMS and LHCb experiments. The measurements are based on a data set collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. Besides the CP violating phase $ϕ_s$, the width difference between the $B_{s}^0$ meson mass eigenstates $ΔΓ_s$ and the average decay width $Γ_s$ are measured. The measured values are then combined with those collected at 8 TeV. The measurements are consistent with theoretic…
The Standard Model predicts CP asymmetries in charm decays of $O(10^{-3})$ and the observation of significantly larger CP violation could indicate non-Standard Model physics effects. During 2011 and 2012, the LHCb experiment collected a sample corresponding to 3/fb yielding the world's largest sample of decays of charmed hadrons. This allowed the CP violation in charm to be studied with unprecedented precision in many two- body and multibody decay modes. The most recent LHCb searches for direct CP violation are presented in these proceedings.
Measurements of Flavor Changing Neutral Current (FCNC) processes (rare decays, flavor mixing) play a key role to pursue new physics beyond the Standard Model. We present recent analysis results about some FCNC transitions performed by CDF and D0 collaborations, including the first observation of the B_s->phi mu^+mu^- mode, the forward-backward asymmetry measurement in B->K^(*) mu^+mu^-, and updated measurements of B_s (B^0)->mu^+mu^-, using data corresponding to integrated luminosities from 3.7/fb to 5/fb. We also show the CDF/D0 combined measurement of the B_s mixing phase using 2.8/fb of dat…
A first measurement of \fplus, the \CP-even content of the decay D->4pi using decays of $ψ(3770)$ to quantum correlated $D\bar{D}$ decays collected by the CLEO-c experiment is presented. The measured value is \fplus=$0.737 \pm 0.028$. This relatively high value makes the decay mode particularly suitable for both measurements of the CKM angle $γ$ and charm \CP-violation in a model independent way. This novel approach to studying indirect \CP-violation in charm decays is based on the time-dependent inclusive analysis of multi body self-conjugate states. These final states can be used to determin…
The sensitivity to $B_s$ meson mixing phenomena can be significantly improved by distinguishing the initial meson flavour. The flavour tagging techniques used in the ATLAS measurement of the angular amplitudes contributing to $B_s \rightarrow J/ψϕ$ decays are presented using 4.9 fb$^{-1}$ of $pp$ data at $\sqrt{s}$ = 7 TeV from 2011. The methods, their performance and calibration on self-tagged $B^\pm \rightarrow J/ψK^\pm$ data are shown.
The LHCb experiment has measured CP violation (CPV) across the Dalitz plot of charmless decays of B+ mesons to 3 charged tracks, namely in Kππ, KKK, πππ and πKK final states, with strikingly large CPV that vary strongly with Dalitz variables. Identifying these processes with b -> sqq(bar), sss(bar) and b -> dqq(bar), dss(bar), where q = u, d, then the "sum rule" that requires two-loop absorptive parts by unitarity works well for inclusive b -> s CPV, but less well for inclusive b -> d case. We elucidate the situation, and argue that the 30 year old unitarity/CPT argument is valid to this day, …
We present measurements of the branching fraction and time-dependent CP-violating (CPV) asymmetries in B0 --> K0S Pi0 decays based on 227 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC. We obtain a branching fraction B(B0 --> K0 Pi0) = (11.4 +/- 0.9 +/- 0.6) x 10^{-6}, the magnitude of the direct CPV asymmetry C = 0.06 +/- 0.18 +/- 0.06 and the magnitude of the CPV asymmetry in the interference between mixing and decay S = 0.35 +0.30/-0.33 +/- 0.04, where the first error is statistical and the second systematic. All results ar…
CP violation (CPV) in the baryon sectors has not yet been established experimentally. In this work, we propose to search for the hyperon CPV through the Cabibbo-favored charm-baryon decaying processes involving a hyperon in the final states, such as $Λ_c^+\to Λ^0π^+, Λ^0\to pπ^-$. The CPV of the hyperon decays are purely revealed in these chain processes, since the CPV in the Cabibbo-favored charm decays are vanishing in the Standard Model (SM). The hyperons are polarized in the weak charm decays, so that we can measure the Lee-Yang asymmetric parameter $α$ by the angular distributions, and th…
We present a measurement of the time-dependent CP-violating (CPV) asymmetries in $B^{0}\to K_{s}^{0}π^{0}$ decays based on 124 million $Υ(4S)\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. In a sample containing $122\pm 16$ signal decays, we obtain the magnitude of the direct CPV asymmetry $C_{K_{s}^{0}π^{0}} = 0.40^{+0.27}_{-0.28} \pm 0.09$ and the magnitude of the CPV asymmetry in the interference between mixing and decay $S_{K_{s}^{0}π^{0}} = 0.48^{+0.38}_{-0.47} \pm 0.06$ where the first error is statistical and the second systema…
We present a brief review of CPV and mixing measurements in the charm sector, with emphasys in results published or presented since the previous edition of the Physics in Collision Symposia.
The K_S \to pi+/- e+ e- decay mode has been investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23k signal events and 59k K_L \to pi+ pi- pi0_D normalization decays, the K_S \to pi+ pi- e+ e- branching ratio was determined. This result is also used to set an upper limit on the presence of E1 direct emission in the decay amplitude. The CP-violating asymmetry has been also measured. We report on measurements of the rare decays K +/- \to pi+/- e+ e- and K+/- \to pi+/- mu+ mu- . The full NA48/2 data set was analyzed, leading to more than 7200 reconstructed events …
We introduce a novel approach to investigate CP violation in the neutrino sector, based on the simultaneous detection of $ν_e$ and $\barν_e$ stemming from the oscillation of $ν_μ$ and $\barν_μ$ produced in the decay at rest of $π$s and $μ$s at a beam dump. This approach relies on a novel liquid scintillator detector technology expected to yield unprecedented identification of $ν_e$ and $\barν_e$ charged-current interactions, which we investigate by means of Montecarlo simulations. Here we report preliminary results concerning both the detection technique and its physics reach.
CP violation (CPV) in $D^0-\overline{D^0}$ mixing is described in terms of the dispersive and absorptive `weak phases' $ϕ_f^M$ and $ϕ_f^Γ$. They parametrize CPV originating from the interference of $D^0$ decays with and without dispersive mixing, and with and without absorptive mixing, respectively, for CP conjugate hadronic final states $f$, $\bar f$. These are distinct and separately measurable effects. For CP eigenstate final states, indirect CPV only depends on $ϕ_f^M$ (dispersive CPV), whereas $ϕ_f^Γ$ (absorptive CPV) can only be probed with non-CP eigenstate final states. Measurements of…
Very recently, the LHCb Collaboration observed the $CP$ violation (CPV) in the charm sector for the first time, with $ΔA_{CP}^{\rm dir}\equiv A_{CP}(D^0\to K^+K^-)-A_{CP}(D^0\to π^+π^-)=(-1.54\pm0.29)\times10^{-3}$. This result is consistent with our prediction of $ΔA_{CP}^{\rm SM}=(-0.57\sim -1.87)\times 10^{-3}$ obtained in the factorization-assisted topological-amplitude (FAT) approach in [PRD86,036012(2012)]. It implies that the current understanding of the penguin dynamics in charm decays in the Standard Model is reasonable. Motivated by the success of the FAT approach, we further suggest…
Hadrons containing b-quarks represent a great opportunity to investigate the flavor sector of the Standard Model (SM) and to look for New Physics effects (NP). In this report we review the most up-to-date results on b-hadron decay rates and CP violating asymmetries: among other results, we report Branching Ratio (BR) and CP Violation (CPV) of B0, B0s and Lambda0b decay modes into pairs of charmless charged hadrons (pions, kaons and protons), the first search for CPV in B0s to phiphi decays and the first observation of bs to K0starK0star decay. Two new results from the CDF collaboration are rep…
While indirect & direct CP violations (CPV) had been established in the decays of strange & beauty mesons, none have been done for baryons. There are different "roads" for finding CP asymmetries in the decays of strange baryons; they are highly non-trivial ones. The HyperCP Collaboration had probed CPV in the decays of single $Ξ$ & $Λ$ [Phys.Rev.Lett 93 (2004) 262001]. We talk about future lessons from $e^+e^-$ collisions at BESIII/BEPCII: probing decays of pairs of strange baryons, namely $Λ$, $Σ$ & $Ξ$. Realistic goals are to learn about non-perturbative QCD. One can hope to find CPV in the …
Recent precise measurements of CP violation parameters in kaon decays at the NA48 experiment: indirect CPV parameter $|η_{+-}|$, and charge asymmetries in $K^\pm\to3π$ decays, are presented.
We analyze the constraints on CP-violating, flavor conserving Two Higgs Doublet Models (2HDMs) implied by measurements of Higgs boson properties at the Large Hadron Collider (LHC) and by the non-observation of permanent electric dipole moments (EDMs) of molecules, atoms and the neutron. We find that the LHC and EDM constraints are largely complementary, with the LHC studies constraining the mixing between the neutral CP-even states and EDMs probing the effect of mixing between the CP-even and CP-odd scalars. The presently most stringent constraints are implied by the non-observation of the ThO…
We investigate the implications of one light eV scale sterile neutrino on the physics potential of the proposed long-baseline experiment DUNE. If the future short-baseline experiments confirm the existence of sterile neutrinos, then it can affect the mass hierarchy (MH) and CP-violation (CPV) searches at DUNE. The MH sensitivity still remains above 5$σ$ if the three new mixing angles ($θ_{14}, θ_{24}, θ_{34}$) are all close to $θ_{13}$. In contrast, it can decrease to 4$σ$ if the least constrained mixing angle $θ_{34}$ is close to its upper limit $\sim 30^0$. We also assess the sensitivity to …
We report a measurement of D0-D0bar mixing in D0->Ks pi+ pi- decays using a time-dependent Dalitz plot analysis. We first assume CP conservation and subsequently allow for CP violation. The results are based on 540 fb$^{-1}$ of data accumulated with the Belle detector at the KEKB $e^+e^-$ collider. Assuming negligible CP violation, we measure the mixing parameters $x=(0.80\pm0.29^{+0.09 +0.10}_{-0.07 -0.14})%$ and $y=(0.33\pm0.24^{+0.08 +0.06}_{-0.12 -0.08})%$, where the errors are statistical, experimental systematic, and systematic due to the Dalitz decay model, respectively. Allowing for CP…
CP-violation (CPV) and Time-reversal violation (TRV) are intimately related through the CPT theorem: if one of these discrete symmetries is violated the other one has to be violated in such a way to conserve CPT. Although CPV in the B0-B0 system has been established by the B-factories, implying indirectly TRV, there is still no direct evidence of TRV. We report on the observation of TRV in the B-meson system performed with a dataset of 468 million BB pairs produced in Y(4S) decays collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Lab…
Although CP violation is predicted to be small in the Standard Model, there exists a continuing theoretical interest within the charm sector due to enhancements of CPV through new physics processes. We present an overview of the measurements of direct CP violation in the charm sector at Belle. We give a brief review of the theory of CP violation in charm physics, then discuss recent measurements for the decay modes $D^{+}_{(s)}\rightarrow ϕπ^{+}$; $D^{0}\rightarrow K^{0}_{S}π^{0}, K^{0}_{S}η^{(\prime)}$; $D^{+}\rightarrow π^{+}η^{(\prime)}$; and $D^{+}\rightarrow K^{0}_{S}π^{+}$.
In a class of new physics models, an extended Higgs sector and new CP-violating sources are simultaneously present in order to explain the baryon asymmetry in the Universe. The aim of this work is to study the implications of beyond the Standard Model (SM) CP violation for the searches of heavy scalars at the LHC. In particular, we focus on the diphoton channel searches in the CP-violating two-Higgs-doublet model (CPV 2HDM). To have a sizable CPV in the scalar sector, the two heavy neutral scalars in 2HDM tend to be nearly degenerate. The theoretical constraints of unitarity, perturbativity an…
Probing CP and flavor violation in neutral kaon decays with ALPs
University of California Santa Cruz（加州大学圣克鲁兹分校）；Santa Cruz Institute for Particle Physics（圣克鲁兹粒子物理研究所）；University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
$CP$ violation asymmetry is expected to be very small within the Standard Model. Observation of $CP$ violation in charm sector would hint towards New Physics. Time-reversal asymmetry is sensitive to $CPV$ via the $CPT$ Theorem, and is a clean and alternative way to search for CP violation in charm decays. This is achieved by the use of triple-product correlations in 4-body charm meson decays. The results from previous searches at BaBar and LHCb Collaborations and the latest results from Belle are reported. The most recent result from Belle performed in $D^{0} \to K^{+}K^{-}π^{+}π^{-}$ decays u…
We report on a search for CP violation in the decay $ D^\pm \to K^0_{\scriptscriptstyle S} π^\pm $ using a data set corresponding to an integrated luminosity of $ 469\,\,fb^{-1} $ collected with the \slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R} detector at the PEP-II asymmetric energy $e^+e^-$ storage rings. The CPviolating decay rate asymmetry $A_{CP}$ is determined to be $(-0.44 \pm 0.13 \mathrm{(stat)} \pm 0.10 \mathrm{(syst)})%$, consistent with zero at 2.7 $σ$ and with the standard model prediction of $(-0.332 \pm 0.006)%$. This is currently the most p…
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…
Resonances and final state interactions (FSI) play a role in the formation of CP violation (CPV) constrained by CPT invariance. We provide a general formulation of CPV including resonances and FSI starting from the CPT constraint. Our discussion is elaborated within a simple $B$ decay model with the $ρ$ and $f_0(980)$ resonances plus a non resonant background including the $ππ\to KK$ coupled amplitude. We consider few illustrative examples to show the interference patterns appearing in the CP asymmetry, namely, that from the $ρ$ resonance plus a non-resonant amplitude, and that from the interf…
The D0 meson can decay to the wrong sign K+pi- state either through a doubly Cabibbo suppressed decay or via mixing to the D0bar state followed by the Cabibbo favoured decay D0bar -> K+ pi-. We measure the rate of wrong sign decays relative to the Cabibbo favoured decay to (0.383 +- 0.044 +- 0.022)% and give our sensitivity to a mixing signal.
We report the result of a search for D0 - D0_bar mixing in the data from hadroproduction experiment E791 at Fermilab. We use the D* tag and semileptonic decay vertices of D0 to look for wrong-sign decays with mixing time dependence.
Recent results on Bs mixing, lifetime difference and rare decays obtained by the CDF and DO collaborations using the data samples collected at the Tevatron Collider in the period 2002 - 2005 are presented.
Current status of charm mixing search, lifetime difference measurement and rare decay search are reported. The best upper limit at 95% CL for mixing is reported from the CLEO collaboration. E791 has reported lifetime difference measurement and results of rare decay searches. Rare decay searches of the FOCUS collaboration are in progress and their sensitivities to branching ratios are at the level of a few x 10^{-6}.
We currently live in the age of the CKM paradigm. The $3\times 3$ matrix that links $(d,\ s,\ b)$ quarks to $(u,\ c,\ t)$ in the charged current weak interaction, being complex and nominally with 18 parameters, can be accounted for by just 3 rotation angles and one $CP$ violating (CPV) phase, with unitarity and the CKM phases triumphantly tested at the B factories. But the CKM picture is unsatisfactory and has too many parameters. The main aim of Flavor Physics and $CP$ violation (FPCP) studies is the pursuit to uncover New Physics beyond the Standard Model (SM). Two highlights of LHC Run~1 pe…
I discuss the results on $D^{0}$-$\bar{D}^{0}$ mixing through hadronic as well as semi-leptonic charm decays, rare flavor-changing neutral currents in the charm sector and the lepton flavor violating $τ$ decaying to charged lighter leptons. The results from both BABAR and Belle are presented in this review.
Using the CLEO II.V detector observing e+e- collisions at around 10.6 GeV we search for neutral D mixing in semileptonic D0 decays tagged in charged D* decays. Combining the results from the Kenu and K*enu channels we find that the rate for D mixing is less than 0.0078 at 90% C.L.
Standard model mixing and CP violation are expected to be small in the charm sector. Some argue that only in the presence of new physics do we currently expect to observe these effects. Fermilab experiment E791 has the largest sample of reconstructed charm decays recorded to date. We have made an exhaustive search for D0 D0-bar mixing and CP violation in this data. We present the charm mixing limits on the mixing parameter r_mix using hadronic and semileptonic decays, and also present preliminary limits on the CP asymmetry parameter, A_CP, for Cabibbo suppressed decays.
We present results of a search for $D^0$-$\kern 0.2em\bar{\kern -0.2em D}{}^0$~mixing and a measurement of $R_{\rm D}$, the ratio of doubly Cabibbo-suppressed decays to Cabibbo-favored decays, based on an analysis of $D^0 \to K^{+}π^{-}$ decays in 57.1~${fb}^{-1}$ of data collected at or just below the $Υ{(4S)}$ resonance with the {\slshape BABAR} detector at the PEP-II collider. Our results are compatible with no mixing and no $CP$ violation. At the 95% C.L., allowing for CP violation, we find the mixing parameters ${x^{\prime}}^2<0.0022$ and $-0.056<y^{\prime}<0.039$, and the mixing rate $R_…
The SuperB experiment at the Cabibbo Laboratory will provide new possibilities to study the physics of charm. The potential physics reach of the experiment when performing studies of rare decays, mixing and CP violation in charm decays is presented here and the implications of such measurements for new physics scenarios is discussed.
Recent measurements of mixing and $CP$ violation in charm decays at LHCb are presented. These include searches for direct $CP$ violation in $D^{0}\rightarrow K_{S}^{0}K_{S}^{0}$, $D_{(s)}^{+}\rightarrow h^{+} π^{0} $ and $D_{(s)}^{+}\rightarrow h^{+}η$ decays, and a search for time-dependent $CP$ violation in $D^{0}\rightarrow h^{+}h^{-}$ decays, where $h^{+}$ is either a $π^{+}$ or $K^{+}$ meson.
We have searched for mixing in the D0-D0bar system by measuring the decay-time distribution of D0->K+pi- decays. The analysis uses 90 fb^{-1} of data collected by the Belle detector at the KEKB e+e- collider. We fit the decay-time distribution for the mixing parameters x' and y' and also for the parameter R_D, which is the ratio of the rate for the doubly-Cabibbo-suppressed decay D0->K+pi- to that for the Cabibbo-favored decay D0->K-pi+. We do these fits both assuming CP conservation and allowing for CP violation. We use a frequentist method to obtain a 95% C.L. region in the x'^2 - y' plane. …
We present an analysis of the decay $D^0 \to K^+π^-$ from FOCUS. From a sample of 234 events we find a branching ratio of $\frac{Γ(D^0 \to K^+π^-)}{Γ(D^0 \to K^-π^+)} = (0.430^{+0.062}_{-0.061}\pm 0.031)%$ under the assumption of no mixing and no CP violation. We also present limits on charm mixing.
Based on a dataset acquired by the BaBar experiment running on and near the $Υ(4S)$ resonance from 1999-2002, limits are set on the rate of $D^0$-- $\kern 0.2em\bar{\kern -0.2em D}{}^0$ mixing using the decay mode $D^{*+} \to D^0 π^{+}$, followed by a semi-leptonic decay of the $D^0$. Results are compared to previous BaBar analysis using hadronic decays. We also report on a search for the flavor-changing neutral current decays $D^0 \to e^{+} e^{-}$ ($μ^{+} μ^{-}$) and the lepton-flavor violation decays $D^0 \to e^{\pm} μ^{\mp}$.
