BELLE SEARCH FOR CP VIOLATION IN RADIATIVE AND HADRONIC D DECAYS AT BELLE Tara Nanut on behalf of the Belle Collaboration The XIIIth International Conference on Heavy Quarks and Leptons 6 May 16 1 { Tara Nanut Search for CP violation in D decays 1/1 1
Outline of the talk We present: Preliminary results of the measurement of branching fraction and CP asymmetry in decays on 943 fb 1 of Belle data. D Ñ V γ V φ, K, ρ Results of the study of the rare decay on 83 fb 1 of Belle data. D Ñ γγ Results of the measurement of CP asymmetry in decay D Ñ π π on 966 fb 1 of Belle data. { Tara Nanut Search for CP violation in D decays /1 1
Analysis D Ñ V γ Motivation: Decays D Ñ ρ γ not yet observed Sensitive to New Physics in terms of A CP measurement: SM prediction: Op1 3 q SM extension with chromomagnetic dipole operators: up to several % for V φ, ρ (Phys. Rev. Lett. 19, 17181 No A CP measurement yet in D Ñ V γ Previous results: Belle (PRL 9, 1183 (4: BpD Ñ φγq.6`.7 pstat.q`.15.61.17psyst.q ˆ 1 5 BaBar (PRD 78, 7111 (8: BpD Ñ φγq.73.3.6 ˆ 1 5 BpD Ñ K γq 3...7 ˆ 1 4 3 { Tara Nanut Search for CP violation in D decays 3/1 1
Analysis method B and A CP extracted through normalisation channels to avoid several sources of systematic uncertainties Decay chains: Normalisation channels: D Ñ φγ Ñ K `K γ D Ñ K `K D Ñ K γ Ñ K π`γ D Ñ K π` D Ñ ρ γ Ñ π`π γ D Ñ π`π Branching fraction: B sig B norm ˆ Nsig N norm ˆ εnorm ε sig CP asymmetry: A raw NpD q NpD q NpD q ` NpD q A raw A CP ` A FB ` A ε A sig CP Asig raw A norm raw ` A norm CP 4 { Tara Nanut Search for CP violation in D decays 4/1 1
Analysis method Flavour tag: D from decay D ` Ñ D π`s (also background suppression with requirement on m mpd `q mpd q Signal extraction: simultaneous d fit in mpd q and cospθ H q γ f V f 1 θh D Normalisation modes: Based on previous Belle analysis of same modes (Phys.Lett. B753, 41 (16 Signal extraction: background subtraction in signal window (SW Estimate background in SW from sidebands (LSB, USB: f get on MC pn bkg SW q MC pn LSB`N USB q MC pn bkg SW q DATA f ˆ pn LSB ` N USB q DATA use on data 5 { Tara Nanut Search for CP violation in D decays 5/1 1
Dominant background From decays with π pñ γγq, one photon missed in reconstruction Main peak in mpd q overlapping with signal peak Lots of decay modes (especially K, ρ, high Brs Events / (.39 GeV.5.4 π bkgs. * K π K ρ + K *(143 π + signal.3..1 1.7 1.75 1.8 1.85 1.9 1.95.5 m(d (GeV Devise dedicated π veto to suppress: combine photon with all others, take diphoton mass closest to mpπ q require once E γ ą 75 MeV and once E γ ą 3 MeV feed these two variables to the neural network Final veto rejects 6% of background and 15% of signal 6 { Tara Nanut Search for CP violation in D decays 6/1 1
Fit results D Ñ φγ Events / (.78 GeV/c 15 1 D signal φ π remaining combinatorial Events / (.78 GeV/c 15 1 D Efficiency: 9.6% Signal yield: 54 35 Raw asymmetry:.91.66 5 5 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c Events / (.4 1 D Events / (.4 1 D 5 5 1.5.5 1 cos(θ H 1.5.5 1 cos(θ H 1.5.5 1 cos(θ H 1.5.5 1 cos(θ H 7 { Tara Nanut Search for CP violation in D decays 7/1 1
Fit results D Ñ φγ Events / (.78 GeV/c 15 1 D signal φ π remaining combinatorial Events / (.78 GeV/c 15 1 D Efficiency: 9.6% Signal yield: 54 35 Raw asymmetry:.91.66 5 5 Signal enhanced: Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1 D Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1 D Events / (.78 GeV/c 3 1 5 1.5.5 1 cos(θ H 1.5.5 1 cos(θ H 5 1.5.5 1 cos(θ H 1.5.5 1 cos(θ H 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c.ăcospθ H q ă. 7 { Tara Nanut Search for CP violation in D decays 7/1 1
Fit results D Ñ K γ Events / (.78 GeV/c 1 D signal * K π * K η K π + π K π + η K ρ + K π + *(143 combinatorial K* π + K ρ + ( π + γ K π + FSR remaining Events / (.78 GeV/c 1 D Efficiency: 7.8% Signal yield: 914 396 Raw asymmetry:.. 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c Events / (.4 1 D Events / (.4 1 D 5 5.5 cos(θ H.5 cos(θ H.5 cos(θ H.5 cos(θ H 8 { Tara Nanut Search for CP violation in D decays 8/1 1
Fit results D Ñ K γ Events / (.78 GeV/c 1 D signal * K π * K η K π + π K π + η K ρ + K π + *(143 combinatorial K* π + K ρ + ( π + γ K π + FSR remaining Events / (.78 GeV/c 1 D Efficiency: 7.8% Signal yield: 914 396 Raw asymmetry:.. Signal enhanced: Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1 D Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1 D Events / (.78 GeV/c 4 5.5.5 cos(θ H cos(θ H 5.5.5 cos(θ H cos(θ H 1.7 1.8 1.9 mass D (GeV/c 5 5 1.7 1.8 1.9 mass D (GeV/c.ăcospθ H q ă. 8 { Tara Nanut Search for CP violation in D decays 8/1 1
Fit results D Ñ ρ γ Events / (.78 GeV/c 4 signal ρ π D K ρ + ρ + π ρ π + remaining combinatorial ρ( π γ π π + π FSR Events / (.78 GeV/c 4 D Efficiency: 6.8% Signal yield: 5 85 Raw asymmetry:.64.151 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c Events / (.4 4 D Events / (.4 4 D.5.5 cos(θ H cos(θ H 5 5.5.5 cos(θ H cos(θ H 9 { Tara Nanut Search for CP violation in D decays 9/1 1
Fit results D Ñ ρ γ Events / (.78 GeV/c 4 signal ρ π D K ρ + ρ + π ρ π + remaining combinatorial ρ( π γ π π + π FSR Events / (.78 GeV/c 4 D Efficiency: 6.8% Signal yield: 5 85 Raw asymmetry:.64.151 Signal enhanced: Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 4 D Events / (.4 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c 4 D Events / (.78 GeV/c 3 1.5.5 cos(θ H cos(θ H 5 5.5.5 cos(θ H cos(θ H 1.7 1.8 1.9 mass D (GeV/c 1.7 1.8 1.9 mass D (GeV/c.3ăcospθ H q ă.3 9 { Tara Nanut Search for CP violation in D decays 9/1 1
Normalisation channels Efficiency Yield A raw rˆ1 3 s K `K.7% 3674. 1.7 K π` 7.% 4.ˆ1 6 1.3.5 π`π 1.4% 17683 8. 3. D Ñ K `K D Ñ K π` D Ñ π`π Events / (.11 GeV.8 data MC.7.6 Events / (.11 GeV.8.7.6 Events / (.11 GeV.6.5.4.5.5.4.4.3.3.3....1.1.1 1.85 1.9 m(d (GeV 1.8 1.84 1.86 1.88 1.9 1.9 m(d (GeV 1.85 1.9 m(d (GeV 1 { Tara Nanut Search for CP violation in D decays 1/1 1
Systematic uncertainties D Ñ φγ D Ñ K γ D Ñ ρ γ Br[%] A CP [ˆ1 3 ] Br[%] A CP [ˆ1 3 ] Br[%] A CP [ˆ1 3 ] γ rec. eff. m 1.16 1.16 1.16 π veto.5.5.5 E9{E5.96.96.96 signal parametrisation 1.39.3.33 4.9 bkg. parametrisation.95.3.81.41 3. 3.78 norm. modes systematics.5.46..1.14.54 total 3.6.64 3.8.41 4.58 5.74 Table: Systematic uncertainties. 11 { Tara Nanut Search for CP violation in D decays 11/1 1
Results (PRELIMINARY Branching fractions: BpD Ñ φγq p.76..8q ˆ 1 5 BpD Ñ K γq p4.66.1.18q ˆ 1 4 BpD Ñ ρ γq p1.77.3.8q ˆ 1 5 consistent with results by Belle, BaBar 3.3σ away from BaBar result (p3...7q ˆ 1 4 first observation ą 5σ significance CP asymmetries: A CP pd Ñ φγq p.94.66.1q A CP pd Ñ K γq p.3..q A CP pd Ñ ρ γq.56.151.6 First measurement of A CP. Results consistent with no CP violation. 1 { Tara Nanut Search for CP violation in D decays 1/1 1
Analysis D Ñ γγ arxiv:151.99 (Accepted by PRD Motivation: Decay not observed yet Sensitive to New Physics: SM prediction: B «p1 3q ˆ 1 8 (Phys. Rev. D 66, 149 ( MSSM model, gluino exchange: B «6 ˆ 1 6 (Phys. Lett. B 5, 34 (1 Previous best result: from BaBar collaboration (Phys. Rev. D 85, 9117 (1: BpD Ñ γγq ă. ˆ 1 6 at 9% C.L. 13 { Tara Nanut Search for CP violation in D decays 13/1 1
Analysis method D from decay D ` Ñ D π`s d fit in mpd q and m normalise B w.r.t decay D Ñ K S π Peaking background: From decays with π and/or η decaying to γγ D Ñ π π, D Ñ ηπ, D Ñ ηη, D Ñ KS pñ π π qπ, D Ñ KL π Suppress with π pηq veto and suppression of merged ECL clusters 14 { Tara Nanut Search for CP violation in D decays 14/1 1
Signal extraction Signal fit on data: Events/(15 MeV/c 6 5 4 3 1 signal peaking bkg. combinatorial 1.7 1.75 1.8 1.85 1.9 1.95 M(γγ [GeV/c ] Events/(1 MeV/c 18 16 14 1 1 8 6 4 14 145 15 155 16 M [MeV/c ] Efficiency: 7.3% Signal yield: 4 15 Same fit on normalisation mode: Efficiency: 7.% Signal yield: 3435 673 15 { Tara Nanut Search for CP violation in D decays 15/1 1
Systematics and result Systematic uncertainties: cut variation signal PDF shape γ rec. eff. KS reconstruction π identification BpD Ñ KS π q 6.8% `4..4 events 4.4%.7% 4.% 3.3% Table: Systematic uncertainties. Calculation of upper limit: use frequentist method to estimate 9% C.L. upper limit Final result: BpD Ñ γγq ă 8.4 ˆ 1 7 at 9% C.L. most stringent upper limit to date 16 { Tara Nanut Search for CP violation in D decays 16/1 1
Analysis D Ñ π π Phys. Rev. Lett. 11, 1161 (14 Motivation: Singly Cabibbosuppressed: enhanced possibility of New Physics contributions to A CP Not measured at Bfactories before Only previous result: by CLEO collaboration (Phys. Rev. D 63, 7111 (1: A CP pd Ñ π π q p.1 4.8q% 17 { Tara Nanut Search for CP violation in D decays 17/1 1
Analysis method Flavour tag: D from decay D ` Ñ D π`s Fit m simultaneously for D, D, in bins of (cospθ q, p π S T, cospθπ S qq, extract A raw for each bin A raw A CP ` A FB ` A π`s ε Determine A π` s ε from tagged and untagged D Ñ K π`, subtract and obtain A corr raw A CP ` A FB in cospθ q bins A FB is an odd function in cospθ q, therefore A CP 1 pacorr raw pcospθ qq ` A corr raw p cospθ qq Obtain average A CP via a χ fit on values in bins of cospθ q 18 { Tara Nanut Search for CP violation in D decays 18/1 1
.5 Fit results D.145.15.155.16 M (GeV/c 3 1 Events/(. MeV/c.5 1.5 1 D Events/(. MeV/c.5 1.5 1 3 1.5.5.145.15.155.16 M (GeV/c Combined signal yield: 3446 73 3 1.145.15.155.16 M (GeV/c.6.4. Events/(. MeV/c.5 1.5 A CP 1..5.4.145.15.155.16 M (GeV/c.6..4.6.8 1 * cos θ.4 19 { Tara Nanut Search for CP violation in D decays 19/1 1
Systematics and result signal shape.3 π S correction.7 A CP extraction method.7 Total.1 Table: Systematic uncertainties. Final result: A CP r.3.64pstat.q.1psyst.qs% Result is consistent with no CPV. { Tara Nanut Search for CP violation in D decays /1 1
Summary D Ñ V γ (PRELIMINARY RESULTS Branching fractions BpD Ñ φγq p.76..8q ˆ 1 5 BpD Ñ K γq p4.66.1.18q ˆ 1 4 BpD Ñ ρ γq p1.77.3.8q ˆ 1 5 first observation! CP asymmetries: A CP pd Ñ φγq p.94.66.1q A CP pd Ñ K γq p.3..q A CP pd Ñ ρ γq.56.151.6 First A CP measurement. No A CP observed. D Ñ γγ BpD Ñ γγq ă 8.4 ˆ 1 7 at 9% C.L. Most stringent limit to date. D Ñ π π A CP pd Ñ π π q p.3.64.1q% No A CP observed. 1 { Tara Nanut Search for CP violation in D decays 1/1 1