D -D mixing and CP violation at LHC Patrick Spradlin on behalf of the LHCb collaboration University of O Particle P 5 th International Workshop on the CKM Unitarity Triangle Rome, Italy 9-13 September 28 Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 1 / 23
Outline 1 LHCb detector LHC LHCb 2 The LHCb trigger Trigger structure Sources of charm 3 CP violation searches Introduction Prompt charm 4 D -D mixing Overview Creation vertex Mixing sensitivity studies Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 2 / 23
LHCb detector Outline 1 LHCb detector LHC LHCb 2 The LHCb trigger Trigger structure Sources of charm 3 CP violation searches Introduction Prompt charm 4 D -D mixing Overview Creation vertex Mixing sensitivity studies Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 3 / 23
LHCb detector LHC Large Hadron Collider Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 4 / 23
LHCb detector LHCb detector LHCb y 5m RICH1 Magnet T1 T2 T3 SPD/PS M2 HCAL ECAL RICH2 M1 25mrad M3 M4 M5 Vertex Locator TT 1mrad 5m 5m 1m 15m 2m z Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 5 / 23
LHCb detector LHCb LHCb features The features that make LHCb excellent for B p also make it a good charm p experiment High event rate Excellent vertexing and proper time resolution: 45 fs for secondary D Good tracking and momentum resolution: 6 MeV D mass Excellent K -π discrimination Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 6 / 23
The LHCb trigger Outline 1 LHCb detector LHC LHCb 2 The LHCb trigger Trigger structure Sources of charm 3 CP violation searches Introduction Prompt charm 4 D -D mixing Overview Creation vertex Mixing sensitivity studies Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 7 / 23
LHCb trigger The LHCb trigger Trigger structure L hardware trigger high p t particles Including Calorimeter hadrons E t > 3.5 GeV; Muon p t > 1.5 GeV Input 4 MHz 1 MHz output Efficiently favors bb events over prompt charm HLT1 first stage software trigger Parallel trigger paths: alleys Partial reconstruction of limited detector information Fast identification of general B event features High p t particles (hadrons, muons, electrons, and photons) Charged tracks with sizable impact parameter HLT2 second stage software trigger Channels for specific interesting decays Fast final state candidate reconstruction Composite decay chain reconstruction, e.g., D + π s + D (h h + ) 2 khz total output rate Potentially up to 3 Hz for D /charm Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 8 / 23
The LHCb trigger Uses of LHCb D + trigger Sources of charm ratio 1 Charm p.8 K K, p fraction /.5 MeV bin.3.25.2.15.1 RS signal WS double mis-id background WS random π s background WS combinatoric background.6.4.2 all kaons pt>1 GeV,pions pt>1 GeV kaons, pions from calibration sample, pt>1 GeV π K, p 1 2 3 4 5 6 7 8 9 1 P(GeV).5 14 145 15 155 16 m = m πs Kπ - m Kπ (MeV) RICH calibration Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 9 / 23
The LHCb trigger Sources of charm Two sources of charm B decays (B D ( ) X ) + Strongly favored by LHCb triggers + Potentially less background - New techniques need to be developed no published measurements Prompt production in primary interaction Triggered less efficiently compensated by prolific production - Potentially larger backgrounds + CDF has proven that measurements are possible in hadronic environment Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 1 / 23
CP violation searches Outline 1 LHCb detector LHC LHCb 2 The LHCb trigger Trigger structure Sources of charm 3 CP violation searches Introduction Prompt charm 4 D -D mixing Overview Creation vertex Mixing sensitivity studies Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 11 / 23
CP violation searches Introduction CP violation searches Looking for unambiguous signs of New P in as many channels as possible (A vital part of any charm p program) Both time integrated and time dependent CPV searches Two body K π, K K +, and π π + modes Three body charged and neutral decays Amplitude analyses D K S π + π, K S K + K, K S K π; D + K + K π +, K ππ Four body decays Quantities odd under T Amplitude analyses (analysis code already exists in LHCb) D K + K π + π, K πππ Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 12 / 23
CP violation searches Introduction CPV in D K K + (and π π + ) Data set N(K K + ) A CP (K K + )(%) Belle 54 fb 1 12 1 3.43 ±.3 ±.11 BaBar 386 fb 1 13 1 3. ±.34 ±.13 CDF 123 pb 1 16 1 3 2. ± 1.2 ±.6 HFAG Avg.16 ±.23 LHCb 1 fb 1 8 1 6 A CP ±.4 (stat) Entries/3 MeV/c 2 CDF II 5 4 3 2 *+ - D D π + [K K + ]π + + charge conjugate Entries/4 MeV/c 2 5 4 3 2 CDF II from secondary D + *+ - D D π + [π π + ]π + + charge conjugate Similar analysis with D π π + 1 1.75 1.8 1.85 1.9 1.95 2 KK Mass [GeV/c ] 1 1.78 1.8 1.82 1.84 1.86 1.88 1.9 2 ππ Mass [GeV/c ] CDF direct CPV search Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 13 / 23
CP violation searches Prompt charm Developments with prompt charm Preliminary selection with promptly produced D show promise. D Mass Simulated 35 4.9 s Events 3 25 2 15 1 5 h2 Entries 129 Mean 1866 RMS 9.327 182 184 186 188 19 192 D Mass (MeV) Prompt RS signal (red) and background (blue) in simulated minimum bias events after L trigger. Preliminary selection for prompt D hh Selection rates after L trigger: D K π + (RS): 23 Hz D K K + : 2 Hz Reasonable backgrounds Preliminary S/B 5 Random π s background under control S/B(Rnd π s) 9 Promising tagging purity for CPV measurements Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 14 / 23
CP violation searches Prompt charm Prompt charm sample Estimated selection yields in 1 fb 1 1 fb 1 Yield: Secondary selection Prompt selection K π + RS 62 1 6 12 1 6 K K + 8 1 6 1 1 6 Secondary yield estimates include L and HLT. Selection optimized for WS π K +, and may not be optimal for K K +. Prompt yield estimates include L, but do not include HLT. Selection of prompt D K K + for Tagged CPV measurement Tagged and Untagged y CP measurements Lifetime measurements Use precisely estimated primary vertex Acceptance effects can be derived in data Efficient implementation in HLT under study. Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 15 / 23
D -D mixing Outline 1 LHCb detector LHC LHCb 2 The LHCb trigger Trigger structure Sources of charm 3 CP violation searches Introduction Prompt charm 4 D -D mixing Overview Creation vertex Mixing sensitivity studies Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 16 / 23
D -D mixing Overview Mixing measurements at LHCb Precise mixing measurements Measure CP violation in mixing Determine relative values of x and y dominant mixing processes WS D π K + mixing analysis Sensitive to x 2 and y BaBar 3.9σ evidence, CDF 3.8σ evidence Requires measurement of strong phase δ by CLEO / BES-III Two body lifetime ratio measurement of y CP SCS D K K + and π π + Belle 3.2 σ evidence, BaBar 3 σ evidence Amplitude analysis of D K S π + π Sensitive to x and y. Powerful technique used by CLEO and Belle Mixing measurements in D 4h Preliminary: up to 25 1 6 RS D (4h) events per 2 fb 1 to tape 4-body amplitude analysis already in development at LHCb Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 17 / 23
D vertex resolution D -D mixing Creation vertex Signal MC lab frame angles *+ D vertex D + π s *+ } D K - π + bin -4 cand / 2 1 12 1 8 6 Lab Frame D daughter angle Lab Frame D -π+ s angle B 4 2 Decay vertex resolutions D D + x 21.6 µm 187. µm y 16.9 µm 144. µm z 257. µm 4232. µm τ.465 ps.98.985.99.995 1 cosθ 1,2 D and π s + almost collinear Add tracks at birth vertex D flight distance at 6 GeV: βγcτ 4 mm Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 18 / 23
D -D mixing Creation vertex Birth vertex improvement for secondary charm x sis Use additional tracks at production vertex B vertex B part D + π s *+ } D K - π + 76% of D + from B s have at least one charged sister Use 1 additional track to partially reconstruct parent B Decay vertex resolutions D D + B part x 21.6 µm 187. µm 18.1 µm y 16.9 µm 144. µm 18.4 µm z 257. µm 4232. µm 237. µm Improved proper time resolution =.45 ps cand /.6 ps bin 16 D lifetime, reconstructed 14 12 1 8 6 4 2-1 1 2 D lifetime (ps) D lifetime, generated Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 19 / 23
D -D mixing Mixing sensitivity studies Sensitivity study of WS mixing Investigate sensitivity to x 2 and y 1-D fit to proper time Γ(t; D π K + ) e [ Γt R D + R D y Γt + 1 4 (y 2 + x 2 )(Γt) 2] Based on secondary charm selection 1 fb 1 of simulated signal ev/toy Exponential background exp ( t/τ D ) Acceptance and resolution effects Fit to x 2 and y Log Events /.3 ps bin 5 1 4 1 3 1 2 1 1 1 Data Signal + Background DCS Signal Background Interference Mixing 1 2 Proper Time (ps) Data set N WS x 2 ( 1 3 ) y ( 1 3 ) BaBar 384 fb 1 43.22 ±.3 ±.21 9.7 ± 4.4 ± 3.1 Belle 4 fb 1 424.18 +.21.23.6 +4. 3.9 CDF 1.5 fb 1 127.12 ±.35 8.5 ± 7.6 LHCb 1 fb 1 2325 x 2 ±.64 (stat) y ±.87 (stat) Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 2 / 23
D -D mixing Sensitivity study of lifetime ratio Mixing sensitivity studies Compare lifetimes of the non-eigenstate RS decay D K π + and CP even decays D K K + (π π + ) [ ] τ(d y CP K π + ) τ(d (K + K,π + π ) 1 = y cos φ x sin φ R 2 m 1 2 Based on secondary charm selection 2 fb 1 of simulated signal ev/toy Exponential background exp ( t/τ D ) Acceptance and resolution effects included Data set N(K K + π s ± ) y CP (%) Belle 54 fb 1 111 1.31 ±.32 ±.25 BaBar 384 fb 1 7 1.3 ±.33 ±.19 LHCb 1 fb 1 8 1 6 y CP ±.5 (stat) cand / bin 7 6 5 4 3 2 1 Acceptance χ 2 / ndf 6.48 / 9 Asymptote, A 67.35 ± 6.47 Intercept, r i.6779 ±.148 Γ acc 2.481 ± 2.71.5 1 1.5 2 D proper time (ps) Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 21 / 23
D -D mixing Summary of LHCb at 1 fb 1 Mixing sensitivity studies Toy statistical 1, 2, and 3 σ contours for secondary WS mixing (ellipses) and K K + y CP studies (bars) in 1 fb 1 of LHCb data. y.9.85.8.75.7.65.6.55.5.45.4 Central Value WS 1 Sigma WS 2 Sigma WS 3 Sigma y 1 sigma CP y 2 sigma CP y 3 sigma CP -3 1 -.1.1.2 2 x Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 22 / 23
Summary Summary First collisions at LHC are imminent LHCb will record unprecedented numbers of charm events Efforts are underway to exploit both prompt and secondary sources for charm p analyses We look forward to making significant contributions to charm p! Patrick Spradlin (O University) D -D mixing and CP violation at LHC CKM8 WG IV 28.9.12 23 / 23