Wolfgang Menges, Queen Mary Giampiero Mancinelli University of Cincinnati CHARM 2007 – Cornell, USA Experimental Prospects for CP and T Violation Studies in Charm

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Outline THE RESEARCH CP Violation in the Charm Sector Direct CP Violation Experimental Techniques CP/T Violation Searches Charged D decays Neutral D decays CP states 3-Body CP Violation at the  (3770) T-odd Correlations Summary: Current Status Future Prospects Conclusions THE PLAYERS CLEO-c BESIII E-791 SUPER-KEK

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Charming CP Violation Sakharov conditions for baryogenesis (1967): Baryon number violation CP violation Non-equilibrium SM CP Violation in kaon and beauty systems too small Need other sources Three types of CP Violation CPV in mixing matrix (tiny) CPV in decay amplitudes CPV in interference between mixing and direct decay, for a subset of final states (mixing suppressed, hence very small) See previous session for CPV in mixing

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Direct CP Violation in Decay Two amplitudes with different strong & weak phases needed to observe CPV (in SM from tree and penguins) THE DECAYS Cabibbo Favored (CF) Singly Cabibbo Suppressed (SCS) Doubly Cabibbo Suppressed (DCS) strong phase difference c s u W+W+ u W+W+ c s s s e.g. SCS D 0 → K + K - K+K+ K-K- K-K- K+K+ u D0D0 D0D0 2 weak amplitudes with phase difference u u u s Only SCS decays probe penguins

Giampiero Mancinelli, University of Cincinnati – CHARM /25 CP Violation in the Standard Model Standard Model charm physics is “CP conserving” 2x2 Cabibbo quark mixing matrix is real (no CPV at tree level) CPV in penguins and loops (by virtual b quarks) Diluted weak phases in SCS decays In mixing, CPV enters at O(V cb V ub /V cs V us ) In decay, penguin CPV enters at O(V cb V ub /V cs V us  s /  ) No weak phases in CF and DCS decays …except D +  K 0  + - SM ~0.003 (CPV in K 0 decay) Note: in general we can separate direct and indirect CP Violation by: Combine measured A CP with time-dependent CPV measurements (both for CP eigenstates) Just using time-integrated measurements (assuming negligible new CPV in CF or DCS decays): The time-integrated CP asymmetry for CF decay to a CP eigenstate gives indirect A CP e.g: A CP_DIRECT (P + P − ) = A CP (P + P − ) − A CP (K S 0  0 ), P = K,  Light readings: New physics and CP violation in singly Cabibbo suppressed D decays. Y. Grossman, A. L. Kagan, Y. Nir, Phys.Rev.D75:036008,2007. “I Know She Invented Fire, But What Has She Done Recently?" - On The Future Of Charm Physics, I.I. Bigi, Int.J.Mod.Phys.A21: ,2006. Mixing and CP-violation in charm. A. A. Petrov, Nucl.Phys.Proc.Suppl.142: ,2005. A Cicerone for the Physics of Charm, S. Bianco, F. L. Fabbri, D. Benson, I. Bigi, Riv. Nuovo Cim. 26N7 (2003) 1.

Giampiero Mancinelli, University of Cincinnati – CHARM /25 CP Violation and New Physics (NP) Extensions of the Standard Model (ex: SUSY) contain CP violating couplings that should show up at some level (1%?) in flavor physics Precision measurements and theory are required to detect the NP BSM Physics: charm is unique probe of the up type quark sector, especially models in which CKM mixing is generated in the up sector top quarks: do not hadronize No T 0 -T 0 oscillations Hadronization helps observability of CP Violation up quarks :  0, η and η′ do not decay weakly No  0 -  0 oscillations possible CP asymmetries mostly excluded by CPT theorem) (relatively) Large statistics Flavor models where the CKM mixing is “generated” in the up sector predict large D − D mixing and sizable CPV in D, but smaller effects in the B sector SCS D decays are now more sensitive to gluonic penguin amplitudes than are charmless B decays CF and DCS decays: Direct CPV in charm would mean NP SCS decays: SM ~ from CKM matrix

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Experimental Approaches for DCPV  Measure asymmetry in time integrated partial widths  Measure asymmetries in final state distributions on Dalitz plots  Exploit quantum coherence of DD produced in  (3770) decays  Study T-violation in 4-body decays of D mesons (assuming CPT) with triple product correlations (T-odd) All analyses (except CLEO-c) share many common features Many D 0 s produced in colliders, Easy to determine the flavor of the D 0 (by unbiased tag: D*   D 0   ) Common backgrounds (e.g. K  ) Random  combining with a real D 0  K +  - Multibody D 0 decay from D*   D 0   Random K   combinatoral background Signal and Background yields taken from m K  vs  M(D*-D 0 ) Signal shape/resolution functions/efficiency calibrations taken from CF modes p(D*) cut to suppress from B  D*  D decays Often normalize asymmetries to CF (or other) modes Keep many systematics to a minimum

Giampiero Mancinelli, University of Cincinnati – CHARM /25 BABAR K−K++K−K++ K+K--K+K--  +  - K *0 K + K *0 K - K−K++K−K++ K+K--K+K-- ~42500 events 80fb -1 D + → K − K +  +,  -  +  + ~55000 events 80pb pb -1 D + → K − K +  + D+ → -++D+ → -++ CDFII Large statistics gives access to detailed features in Dalitz plots Phys. Rev. D71, (2005) m(  -  +  + ) m2(-+)m2(-+) m2(-+)m2(-+)

Giampiero Mancinelli, University of Cincinnati – CHARM /25 D 0  K  Yield: 180K 123 pb -1 D 0  KK,  - I SM CPV~10 -3 in single Cabibbo suppressed modes (KK,  ), but null in Cabibbo allowed (K  ) BR(D 0 ->KK) >> BR(D 0 ->  ) (R~2.8) – Large FSI and/or penguin contributions NP CP asymmetries Standard Model (Buccella et al, 1995)  KK: (0.01 ± 0.08)%,  : (0.002 ± 0.001)% CDF II Use D 0  K  as normalization mode D 0  KK Yield:  200 D 0   Yield: 7334  97 Issues: Tracking charge asymmetry partially reconstructed D background for KK mode Phys. Rev. Lett. 94, (2005)

Giampiero Mancinelli, University of Cincinnati – CHARM /25 BABAR Analysis Difficulties: Precise quantification of asymmetry in D 0 flavor tagging Forward-backward asymmetries in cc production (novel issue) Interference in e−e+ -> cc as mediated by either a virtual photon or a virtual Z 0. Higher-order QED box- and Bremsstrahlung-diagram interference effects Can produce asymmetries due to boost of the CMS relative to the lab at asymmetric BABAR Data corrected for charge-dependent detection efficiencies By tagging with an independent sample of D 0 decays Systematics: All corrections used for data will be calculated from data. Goal: reduce systematics in these measurements to the 0.1% level Soft-Pion Tagging efficiency corrections calculated from the CF decay (K  ) With 400 fb -1 we expect: KK   (A CP )= ~ (stat.)    (A CP )= ~ (stat.) Both results expected to be statistically dominated D 0  KK,  - II

Giampiero Mancinelli, University of Cincinnati – CHARM /25 CLEO-c’s Measurements New! 281 pb -1 At the  (3770) Pure DD final state, no additional particles Low particle multiplicity (DD) = 6.4 nb (  (4S)  BB ~ 1 nb) Single tag sample Mostly CF modes High efficiencies SCS Uncertainties ~1% most cases Charged Kaon tracking largest syst. ~0.7%

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Why Dalitz Plot Analyses? In case of indirect CPV and final CP eigenstates the time integrated and time dependent CP asymmetries are: Universal Equal to each other In contrast, for direct CPV: The time-integrated asymmetries are not expected to be universal Parts of phase-space might have different asymmetries They may even cancel each other out when integrated over the whole phase-space New Physics might not show up in the decay rates asymmetries It could show up simply in the phase difference between amplitudes!

Giampiero Mancinelli, University of Cincinnati – CHARM /25 3-Body Dalitz Plot Analyses - I 3-Body decays permit the measurement of phase differences The Dalitz plot technique allows: Increased sensitivity to CP asymmetry Probes the decay amplitude rather than the decay rate. Access to both CP eigenstates (e.g. D 0  0, f 0  0,  0  0, …) and non eigenstates (e.g. D 0  +-  -+, K* +- K -+, …) with relatively high statistics in the modes D 0  -  +  0, D 0  K - K +  0, … As measurements are normalized to the whole phase space, the flavor dependence of  s tagging efficiency is null and the effect of mistagging is very small. CLEO D 0  -  +  0 - Difference in the integrated coherent sum of all amplitudes across the Dalitz Plot between D 0 and D 0 events D 0  K S  -  + - Full Dalitz analysis (see next slide)

Giampiero Mancinelli, University of Cincinnati – CHARM /25 3-Body Dalitz Plot Analyses - II BABAR (expect results this Fall) D 0  -  +  0, D 0  K - K +  0 MODEL DEPENDENT approach: fit D 0 and D 0 Dalitz plots separately, with a resonance (isobar) model (higher systematic uncertainties) Parameterize the amplitude coefficients explicitly in the form: A e iδ = a e i(α + β) (1 + b/a) (for D 0 ) A' e iδ' = a e i(α - β) (1 - b/a) (for D 0 ) Calculate |b| / |a|,  values, asymmetries in the fit fractions for each isobar. Follows CLEO’s K S  analysis technique, ( Phys.Rev.D70:091101,2004). MODEL INDEPENDENT approach: use moments of the cosine of the helicity angle for each of the three channels ( h - h +, h -  0, h +  0 ); plot vs invariant mass. Measure asymmetry in these moments. The phase/interference information is (mostly) contained in the odd moments Decay rate asymmetry is contained in the even moments. D 0 → ρ 0 π 0 b=-0.05  = -5 o D 0 → ρ 0 π 0 b=0  =0 D 0  -  +  0 MC m2(-+)m2(-+) m2(-+)m2(-+) m2(-+)m2(-+) m2(-+)m2(-+)

Giampiero Mancinelli, University of Cincinnati – CHARM /25  (3770): Quantum Correlation Analysis - I Pure J PC = 1 -- initial state  CP+ If a D 0 (tag) decays to a CP eigenstate f 1, CP conservation requires the recoiling state f 2 to have a definite CP as well, which must be of opposite sign: e + e -   (3770)  D 0 D 0 e+e+ ee  ++ K+K+  Quantum Correlation Analysis (TQCA): Due to quantum correlation between D 0 and D 0, not all final states allowed. CP(f 1 f 2 ) = CP(f 1 ) CP(f 2 ) (-1) l = CP+ - - (since l = 1) e.g. K + K -  D CP   ’’(3770)  D CP  K s  0 (-1) l = CP+ At the  (3770) (CLEO-c) 22% double tagging efficiency  (4S)) Same number of DD fully reconstructed as  (4S) Unique CPV search strategy Complementary to other experiments

Giampiero Mancinelli, University of Cincinnati – CHARM /25 K -  + vs K -  + K -  + vs K +  - CP+ vs CP+ CP- vs CP- K  vs CP+ K  vs CP- CP+ vs CP-  (3770): Quantum Correlation Analysis - II Reconstruct both D mesons (double tag) Maximal constructive interference Forbidden by CP Conservation Data favors QC interpretation: constructive and destructive interference and no D mixing CP+ CP- CP+CP- KK KK KK KK KK CP± KK XK  l  Interference of Cabibbo Favored with Doubly Cabibbo Suppressed Unaffected Forbidden (Bose Symm., if no D mixing / =  re  i  New! Data consistent with no C+ initial state, (  ~1.5%, stat dominated) “hence” no CPV Improved technique + K L CP+ modes Interference: Two paths to K -  + vs K +  pb -1 cos  = 1.06  0.19  0.06

Giampiero Mancinelli, University of Cincinnati – CHARM /25 T Violation: T-odd Correlations Some references: E. Golowich and G. Valencia, Phys. Rev. D 40, 112 (1989) I.I. Bigi, Proceedings of KAON2001, 417 (2001) (*) I.I. Bigi, A.I. Sanda,‘CP Violation’, Cambridge University Press 2000 We can build T-odd asymmetries as: And the T-Violation asymmetry as: tests T-Violation even with strong phases Method searches for Triple Product Asymmetries in (e.g.) D 0 → K − K +  −  + T-odd correlations can be formed using the momenta of the decay products (and assuming validity of the CPT theorem): Under time reversal T, C T → −C T. C T <>0 does not necessarily established T-Violation, because FSI can “fake” this asymmetry(*) Consider D 0 → K + K -  +  - where we can compute: Finding: establishes T violation.

Giampiero Mancinelli, University of Cincinnati – CHARM /25 T-Violation Measurements FOCUS Yield: fb-1 Yield: ~32000 BABAR Preliminary D 0 → K S 0 K +  −  + D 0 → K − K +  −  +

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Direct CP/T Violation Results – D 0 Decays Experiment (year)Decay mode A CP (%)Comments CDF (2005)D 0  K + K  1.2  0.6 CLEO (2002)D 0  K + K  2.2  0.8 FOCUS (2000)D 0  K + K  2.2  1.5 CDF (2005)D 0   +   1.3  0.6 CLEO (2002)D 0   +   3.2  0.8 FOCUS (2000)D 0   +   3.9  2.5 CLEO (2001)D 0  K 0 S K 0 S - 23  19 CLEO (2001)D 0   0   4.8 CLEO (2001)D 0  K 0 S   1.3 CLEO (1995)D 0  K 0 S  2.8  9.4 CLEO (2005)D 0   +  -  0 1 (+9-7)  5Dalitz plot – integr. CLEO (2004)D 0  K 0 S  +   2.1 ( )Dalitz plot analysis BELLE (2005)D 0  K +  +  -   4.4A of ratios DCS/CF FOCUS (2005)D 0  K + K -  +   5.6  4.7 CLEO (2007)D 0  K -   0.5  0.9 CLEO (2007)D 0  K -  +   0.4  0.8 CLEO (2007)D 0  K -  +  +   0.5  0.9 BELLE (2005)D 0  K +  -   5.3A of ratios DCS/CF BABAR (2007)D 0  K +   5.2  1.5A of ratios DCS/CF BELLE (2007)D 0  K +   4.7A of ratios DCS/CF FOCUS (2005)D 0  K + K -  +   5.7  3.7T violation - TPCor Partial list New!

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Direct CP/T Violation Results – D + Decays Experiment (year)Decay mode A CP (%)Comments BABAR (2005)D +  K - K +   1.0  0.8A of ratios SCS/CF BABAR (2005)“ D +    1.5  0.6Resonant substructure of D +  K - K +  + BABAR (2005)“ D +  K *0 K  1.7  0.7 CLEO (2007)D +  K - K +   1.5  0.8 FOCUS (2000)D +  K - K +   1.1  0.5A of ratios SCS/CF E791 (1997)D +  K - K +   2.9A of ratios SCS/CF E791 (1997)“ D +    3.6Resonant substructure of D +  K - K +  + E791 (1997)“ D +  K *0 K  5.0 FOCUS (2002)D +  K 0 S   1.5  0.9 CLEO (2007)D +  K 0 S   1.0  0.3 CLEO (2007)D +  K 0 S  +   0.9  0.3 CLEO (2007)D +  K 0 S  +  +   1.1  0.6 CLEO (2007)D +  K -  +   0.4  0.9 CLEO (2007)D +  K -  +  +   0.9  0.9 CLEO (2007)D S +  K +  - 20  18 CLEO (2007)D S +  K +  ’- 17  37 CLEO (2007)D S +  K 0 S   27  11 CLEO (2007)D S +  K +   2  29 E791 (1997)D +   +  -   4.2A of ratios SCS/CF FOCUS (2005)D +  K 0 S K +  +   6.2  2.2T violation through triple product correlations FOCUS (2005)D S +  K 0 S K +  +   6.7  2.3 Ne w! Partial list New !

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Average Result, by Mode Decay modeA CP (%) D 0  K + K  ± 1.2 D 0  K S 0 K S 0   2.3 ± 1.9 D 0   +   ± 1.3 D 0   0  ± 4.8 D 0   +    ± 9 D 0  K S   ± 1.3 D 0  K   ± 1.0 D 0  K   +  ± 0.9 D 0  K   +  +  ± 1.0 D 0  K +    0.8  0.8 ± 3.1 D 0  K +    0   0.1 ± 5.2 D 0  K S   +     0.9 ± 4.2 D 0  K +    +     1.8 ± 4.4 D 0  K + K   +     8.2 ± 7.3 D+  KS +D+  KS +   0.9 ± 0.9 D +  K S   +  ± 0.9 D +  K S   +  +   1.3 Decay modeA CP (%) D +  K -  +   1.0 D +  K -  +  +   1.3 D +  K S  K ± 6.2 D +  K + K   ± 0.8 D +   +    +   1.7 ± 4.2 D +  K S  K +  +     4.2 ± 6.8 AT AT SCS modes For most references See the HFAG pages Partial list HFAG + my averages

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Future Prospects – Current Efforts - I D 0  KK,  CDF yield prospects 2M D* tagged D 0  K  per 1 fb -1  A CP ) ~ is achievable with full Tevatron run (4-9 fb -1 ) - at SM limit Issue will be if trigger can cope with Luminosity increase BABAR: 1 ab -1 KK  (A)~0.2% (stat)   (A)~0.3% (stat) D +  K + K -   BABAR – now  (A)~0.45 (systematically dominated – (syst~0.8)) 1 ab -1  (A)~0.28% (stat) Dalitz Analysis: fit fractions and phase differences ~ 1% and 1 o precisions D 0   +  -  0 Dalitz Analysis BABAR 200,000 signal 1 ab -1 in 1  mass region.  (A) (stat) ~ 0.25 % (integrated) If the asymmetry is larger, but confined to only a part of the phase-space or only to certain specific decay(s), or both (constructively) in amplitude phases and magnitudes, our observation potential might be higher (or lower if destructively)

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Future Prospects – Current Efforts - II T-Odd Correlations BABAR (KK  ) now ~ % level (if systematics under control) 1 ab % Relevant datasets I am aware of (larger backgrounds than KK  ): CLEO: D 0   +  -  +  - 7,300 - D 0   +  -  0  0 2,700 – D +   +  -  +  0 5,700 BABAR: D 0   +  -  +  - - current ~140,000 – 1 ab -1 ~320,000 + many large CF decays datasets from all 3 experiments NOTE: Expect similar yields/results from BELLE

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Future Prospects – Future Efforts BEPCII/BESIII Data taking beginning of = 30M DD/yr = 90M DD = ~20 times full CLEO-c dataset Super-B (D,  …) 10 ab -1 /yr at  (4S) With option to lower energy to ~4 GeV (~1ab -1 /yr) LHCb Will implement a dedicated D* trigger stream selecting huge and clean samples of hadronic D modes In one year of running at nominal lumi (2 · cm -2 s -1 ): Expect M D*  D 0  decays with D 0  K  channel = 100 times CDF ! K - K + A < 0.08 (CLEO-c), < (BESIII)  (A) ~1 x (stat.) LHCb/yr  (A) ~6 x (stat.) Super-B/yr  (3770) Quantum Correlation Analysis A < (CLEO-c)  (A) ~0.01 (just KK,  ) (BESIII)  (A) ~7x (stat.) Super-B/yr K S  -  + Dalitz analysis Super-B (5 years = 50 ab -1 ) A < BESIII – SUPER-D-too Factory (KEK and/or Frascati) – LHCb

Giampiero Mancinelli, University of Cincinnati – CHARM /25 Conclusions Charm physics provides unique opportunities for indirect search of NP Theoretical calculation of x, y have large uncertainties Physics BSM hard to rule out from D 0 mixing measurements alone Observation of (large) CPV  robust NP signal SCS D decays now more sensitive to gluonic penguin amplitudes than charmless B decays Exciting new results (CLEO, Belle, BABAR): Total errors ~1% level BUT far from observation Now entering the interesting domain Promising future: Current experiment ~ % in the “best” modes Future efforts (Super-Bs, LHCb, BESIII) ~ %