SEARCH FOR CP VIOLATION IN

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Collaboration The XIIIth International Conference on Heavy

1 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

$Outline of the talk We present: Preliminary results of the measurement of branching fraction$ 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 V γ V φ, K, ρ Results of the study of the rare decay on 83 fb 1 of Belle data.

2 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

3 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, No A CP measurement yet in D Ñ V γ Previous results: Belle (PRL 9, 1183 (4: BpD Ñ φγq.6`.7 pstat.q` psyst.q ˆ 1 5 BaBar (PRD 78, 7111 (8: BpD Ñ φγq ˆ 1 5 BpD Ñ K γq ˆ { Tara Nanut Search for CP violation in D decays 3/1 1

4 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

5 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

6 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 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

7 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: Raw asymmetry: mass D (GeV/c mass D (GeV/c mass D (GeV/c mass D (GeV/c Events / (.4 1 D Events / (.4 1 D cos(θ H cos(θ H cos(θ H cos(θ H 7 { Tara Nanut Search for CP violation in D decays 7/1 1

8 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: Raw asymmetry: Signal enhanced: Events / ( mass D (GeV/c mass D (GeV/c 1 D Events / ( mass D (GeV/c mass D (GeV/c 1 D Events / (.78 GeV/c cos(θ H cos(θ H cos(θ H cos(θ H mass D (GeV/c mass D (GeV/c.ăcospθ H q ă. 7 { Tara Nanut Search for CP violation in D decays 7/1 1

9 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: Raw asymmetry: mass D (GeV/c mass D (GeV/c mass D (GeV/c mass D (GeV/c Events / (.4 1 D Events / (.4 1 D 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

10 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: Raw asymmetry:.. Signal enhanced: Events / ( mass D (GeV/c mass D (GeV/c 1 D Events / ( mass D (GeV/c mass D (GeV/c 1 D Events / (.78 GeV/c cos(θ H cos(θ H cos(θ H cos(θ H mass D (GeV/c mass D (GeV/c.ăcospθ H q ă. 8 { Tara Nanut Search for CP violation in D decays 8/1 1

11 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: mass D (GeV/c mass D (GeV/c mass D (GeV/c mass D (GeV/c Events / (.4 4 D Events / (.4 4 D.5.5 cos(θ H cos(θ H cos(θ H cos(θ H 9 { Tara Nanut Search for CP violation in D decays 9/1 1

12 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: Signal enhanced: Events / ( mass D (GeV/c mass D (GeV/c 4 D Events / ( mass D (GeV/c mass D (GeV/c 4 D Events / (.78 GeV/c cos(θ H cos(θ H cos(θ H cos(θ H mass D (GeV/c mass D (GeV/c.3ăcospθ H q ă.3 9 { Tara Nanut Search for CP violation in D decays 9/1 1

13 Normalisation channels Efficiency Yield A raw rˆ1 3 s K `K.7% K π` 7.% 4.ˆ π`π 1.4% D Ñ K `K D Ñ K π` D Ñ π`π Events / (.11 GeV.8 data MC.7.6 Events / (.11 GeV Events / (.11 GeV m(d (GeV m(d (GeV m(d (GeV 1 { Tara Nanut Search for CP violation in D decays 1/1 1

14 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 π veto E9{E signal parametrisation bkg. parametrisation norm. modes systematics total Table: Systematic uncertainties. 11 { Tara Nanut Search for CP violation in D decays 11/1 1

15 Results (PRELIMINARY Branching fractions: BpD Ñ φγq p.76..8q ˆ 1 5 BpD Ñ K γq p q ˆ 1 4 BpD Ñ ρ γq p q 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 q A CP pd Ñ K γq p.3..q A CP pd Ñ ρ γq First measurement of A CP. Results consistent with no CP violation. 1 { Tara Nanut Search for CP violation in D decays 1/1 1

16 Analysis D Ñ γγ arxiv: (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

17 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

18 Signal extraction Signal fit on data: Events/(15 MeV/c signal peaking bkg. combinatorial M(γγ [GeV/c ] Events/(1 MeV/c M [MeV/c ] Efficiency: 7.3% Signal yield: 4 15 Same fit on normalisation mode: Efficiency: 7.% Signal yield: { Tara Nanut Search for CP violation in D decays 15/1 1

19 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

20 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

21 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

22 .5 Fit results D M (GeV/c 3 1 Events/(. MeV/c D Events/(. MeV/c M (GeV/c Combined signal yield: M (GeV/c.6.4. Events/(. MeV/c A CP M (GeV/c * cos θ.4 19 { Tara Nanut Search for CP violation in D decays 19/1 1

23 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

24 Summary D Ñ V γ (PRELIMINARY RESULTS Branching fractions BpD Ñ φγq p.76..8q ˆ 1 5 BpD Ñ K γq p q ˆ 1 4 BpD Ñ ρ γq p q ˆ 1 5 first observation! CP asymmetries: A CP pd Ñ φγq p q A CP pd Ñ K γq p.3..q A CP pd Ñ ρ γq 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 q% No A CP observed. 1 { Tara Nanut Search for CP violation in D decays 1/1 1

arxiv: v1 [hep-ex] 14 Sep 2015

arxiv: v1 [hep-ex] 14 Sep 2015 WSU HEP XXYY September 5, 5 arxiv:59.3v [hep-ex] Sep 5 Search for CP violation in D K + K, π + π and D π π Tara Nanut Department for Experimental Particle Physics Jozef Stefan Institute, Jamova 39, Ljubljana,