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Improved tests for CP violation in charm decays

Improved tests for CP violation in charm decays. Amarjit Soni ; HET , BNL EPS-2013, Stockholm, Sweden. Outline. Intro : D-system is unique: interesting sensitivity to top “compositeness”; BSM connection SM confronts observed charm CP

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Improved tests for CP violation in charm decays

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  1. Improved tests for CP violation in charm decays AmarjitSoni; HET, BNL EPS-2013, Stockholm, Sweden EPS 7/18/13; A Soni BNL-HET

  2. EPS 7/18/13; A Soni BNL-HET

  3. Outline • Intro: D-system is unique: interesting sensitivity to top “compositeness”; BSM connection • SM confronts observed charm CP • Possible repercussions of Delta I=1/2 Rule understanding from the lattice • FS with possibly enhanced CP • CPT constraints • Possibly critical test for SM or NP • Summary & Outlook EPS 7/18/13; A Soni BNL-HET

  4. Charm system is unique • Sensitive to top physics, example: warp space theory of flavor Delta F=2 mixings are an extremely valuable treasure in providing stringent constraints ……….. EPS 7/18/13; A Soni BNL-HET

  5. Charm CP in the context of a geometric theory of flavor EPS 7/18/13; A Soni BNL-HET

  6. Simultaneous resolution to hierarchy and flavor puzzles EPS 7/18/13; A Soni BNL-HET

  7. Fermion “geography” (localization) naturally explains: Grossman&Neubert; Gherghetta&Pomarol; Davoudiasl, Hewett & Rizzo • Why they are light (or heavy) • FCNC for light quarks are severely suppressed automatically • RS-GIM MECHANISM (Agashe, Perez,AS’04) flavor changing transitions though at the tree level (resulting from rotation from interaction to mass basis)are suppressed roughly to the same level as the loop in SM=> CKM hierarchy • O(1) CP ubiquitous;…..in fact for neutron a (mild) CP problem • Most flavor violations are driven by the top -> ENHANCED t-> cZ, (alsoD0 mixing w & w/o CP)….A VERY IMPORTANT “GENERIC” PREDICTION..Agashe, Perez, AS’06 EXTENSIVE RECENT STUDIES by BURAS et al and by NEUBERT et al EPS 7/18/13; A Soni BNL-HET

  8. Bander Memorial Symposium; 6/8/13; Soni

  9. D-CP Experimental info: 2011--2012 • Measurements of CP violation in D0P+P- show results apparently larger than expected: • Note in particular the >3-sigma signal in the combined result.. EPS 7/18/13; A Soni BNL-HET

  10. VIIIth Rencontres VN, Dec '12; A. Soni

  11. New LHCb Results (Moriond 2013) • Using soft pi D* tag: • Using semileptonic tag for D’s originating from B-hadron decay (note “wrong” sign) • Naïve average of all results is • Again almost 3-sigma signal of CP violation [but opp. sign means experimental numbers are not yet robust] • Taken at face value the new average is bit closer to the quark level estimate EPS 7/18/13; A Soni BNL-HET

  12. Peek @ PDG: old results EPS 7/18/13; A Soni BNL-HET

  13. EXACT U-SPIN LIMIT EPS 7/18/13; A Soni BNL-HET

  14. Taking U-spin breaking into a/c EPS 7/18/13; A Soni BNL-HET

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  19. Summary (so far) on Recent D-CP results • SM explanation cannot be ruled out and is quite plausible; however, a compelling case for SM explanation can also not be made. • Unless true result is , for sure, 1% or more , not a compelling sign of new physics • theory estimates plagued by large hadronic (non-perturbative) uncertainties; NO RIGOUROUS METHOD IN SIGHT; LONG-TERM WORRY => Ghost of  ‘/. However, unlike K->  , lattice methods appear exceedingly difficult • More exptal input (many other modes) crucial & could change interpretation… EPS 7/18/13; A Soni BNL-HET

  20. I=1/2 Rule K=> • A[Ks => + -]/A[K- => - 0 ] ~ 22! • MUCH, MUCH speculations, role of penguins,[SVZ and the like] • Folklore[see e.g. DGH book: section VIII-4]: “the factorization hypothesis works reasonably well in reproducing the experimental value of A2” Pheno2013; A. Soni HET(BNL)

  21. Dissecting 3/2 Amp on the lattice Simplest basic step is Significantly different from phenomenological expectations Pheno2013; A. Soni HET(BNL)

  22. Must try ascertain if D-CP is receiving contribution from BSM Suggestions: Atwood & AS, arXiv:1211.1026 EPS 7/18/13; A Soni BNL-HET

  23. Implications of CPT • Final States with enhanced CP • SM or not : A critical test EPS 7/18/13; A Soni BNL-HET

  24. EPS 7/18/13; A Soni BNL-HET

  25. Candidates for enhanced CP asymmetry[because of CPT] • Since asymmetry arises from T and P interference and as a rule P<<T, need final states where T is suppressed => color suppressed modes: compare D0 => + + - versus 0 0 • 0 0 also gives 4 charged pi’s and possibility of triple correlation asymmetry • Other examples: For KEKB D=> 0 0 (, ’) also imp but may not be CS EPS 7/18/13; A Soni BNL-HET

  26. Propose a new “critical” test for new physics • Key idea: Hadronic matrix elements enhancement (factor O(5) needed for SM explanation) only operational for EXCLUSIVE (in particular 2 body pseudoscalar) MODES • Inclusive (multibody) modes should exhibit quark level asymmetry[quark-hadron duality] ~6X10-4 if SM is the source, if these also show O(3X10-3 ) asymmetry then BSM-CP is the origin • Look forward to imlementation at LHCb, BF & especially KEKB Atwood + AS, arXiv 1211.1026 EPS 7/18/13; A Soni BNL-HET

  27. How to look for inclusive final states? Simple suggestion • Look for D => K K X • Operationally KKX is any final state containing a K K with total energy in the 2 kaonsless than the energy of the parent D EPS 7/18/13; A Soni BNL-HET

  28. Multibody FS can also be very useful • Main point is esp avoid 2-body pseudos as they tend to have significant non-perturbativeeffects. • [Of course tests need be done so that systematics respect CP] • examples: KK + n(pi) with n = 2,3… Pheno2013; A. Soni HET(BNL)

  29. Expected Progress • S(LHCb) • Super-KEKB/BELLEII • Lattice [success of Flavor Physics/Intensity Frontier is intricably tied to the developments on the lattice]though D-CP is highly probematic for now. EPS 7/18/13; A Soni BNL-HET

  30. Summary & Outlook • With 1st observation of dir- CP in charm decays, LHCb has opened a new avenue for probing CPbut experimental numbers need confirmation. • Difficulties in hadronic matrix elements make precise predictions difficult; observed asymmetry ( ACP in KK, ) is perhaps somewhat bigger than simple quark level expectations but may well be just SM (or part of it may be BSM). • Charm system is quite unique and is sensitive to different sources of BSM-CP [e.g. warped theory]; so extremely important to clarify. • Measurements in more modes may help, choose those with charged final mesons : D0=>0 0 , K(*)0 K(*)0 , Ds => 0 K(*)+ ; VV states allow T-odd CP tests w/o need for tagging; and rates are (tree) suppressed so CPT implies larger asymmetries • Suggested search in inclusive D=> K K X events could shed decisive light EPS 7/18/13; A Soni BNL-HET

  31. EXTRA EPS 7/18/13; A Soni BNL-HET

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  35. EW MORIOND; 3/3/13; A. Soni

  36. EW MORIOND; 3/3/13; A. Soni

  37. EW MORIOND; 3/3/13; A. Soni

  38. Mass depends of ReA2, A0 Due to the cancellation, 3/2 amplitude decreases significantly as the pion mass is lowered towards its physical value EW MORIOND; 3/3/13; A. Soni

  39. EPS 7/18/13; A Soni BNL-HET

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