Tau & Charm Physics. Toru Iijima Nagoya University. November 7, 2009 HEC sub-committee for future planning

Transcription

1 Tau & Charm Physics Toru Iijima Nagoya University November 7, 2009 HEC sub-committee for future planning

2 Talk Outline Charm Physics Tau Physics Run (machine) at tau- charm threshold? Super Super Super B factory is also σ ( ee + BB) 1.1nb Tau factory + + σ( ee τ τ ) 0.91nb Charm factory σ ( ee + cc) 1.3nb Physics with O(10 10 ) τ and charm / year

3 Target of Charm Physics 1 Tiny in SM GIM cancellahon NP Search: DD- mixing and CPV O 2 3 (10 ) O(10 ) Double Cabibbo suppressed ( m m )/ m 0 s d W 2 ~ sin θc ~ ηa λ ~ O(10 ) CPV from phase of V cs If larger than expected signal of NP Unique probe for NP coupling to up- type quarks. Golowitch et al. PRD76, (2007) Example: R- violahng SUSY u c u c d % Rk, l Li, d % l Li, Rk, %l Li, d Rk, d %l Rk, Li, c u c u m~ d R k [GeV] X D <0.3% <0.5% <0.8% <1.2% (now) R couplings

4 NP and D-D mixing Golowitch et al. PRD76, (2007)

5 Phenomenology Time evoluhon by flavor states H eff eigenstates: (defined flavour) (defined m 1,2 and Γ 1,2 ) D ± x 0 0 1,2 = p D q D m m Γ, y Γ Γ 2Γ q 1 q 2 P 0 P 0 q 2 q 1 P 0 = K 0, B d0, B s 0 and D 0 ix + 2 y q p ix + 2 Γ imt t D ( t) = D cosh Γt D sinh Γt e y 0 dn ( D f ) Γt 0 q ix + dt e f D + p 2 y f D 0 2 Decay Hme distribuhon of states accessible to D 0, D 0 is sensihve to x and y.

6 Measurements of D-D mixing 3 approaches Decays to CP eigen states: D 0 K + K - /π + π -.vs. K - π + Wrong sign decays: D 0 K - π + Time- dep. Dalitz : D 0 K - π - π 0, K S π + π - AM ycp = ycosφ xsinφ 2 A τ( D K K ) τ( D K K ) Γ = τ( D K K ) + τ( D K K ) AM = y cosφ x sinφ 2 y D ΔΓ D /2Γ D (%) Evidence for D-D mixing! x D ΔM D /Γ D (%)

7 Prospect at Belle II

8 Target of Charm Physics 2 Precision CKM to over constrain NP together with B Our dream Not automatically reached by increasing the statistics Need good understanding for fundamental parameters calculated by laice QCD B decay constant f B V td by B- B mixing, V ub (or H ± )by B τν B π form factor f B π V ub by B π l ν Precise measurements in D decays as calibrahon of laice QCD f D by D µν f D π by D π l ν

9 D decay constant f D / f D 424pb -1 B τ ν f D f D s Br( τν ) = (0.786 ) 10 fit [ ] Br ( τν ) = 1.20 ± SM Based on fb from HPQCD and V ub from HFAG (BLNP, ICHEP08) Based on CKM filer (τν is not included in the fit) HFAG summer08 (1.51±0.33)x10-4 CKM2008 (1.73±0.35)x10-4

10 Target of Charm Physics fb -1 c d u c ψ Bà K π+ π - J/ψ Belle c u u c X(3872) M(π + π - J/ψ) M(J/ψ) b u u b + e + e ϒ+ π + π

11 @ Belle II B 0 --, 1 --, cc ψ ( ) φ ψ ( ) 0 --, , 0 ++, 2 ++ Super B-Factory ccus bbud 11

12 Why do we want to study τ decays? Many physics involved in the produchon and decays. Goof probe for ElectromagneHc interachon Weak interachon Strong interachon Small theory errors Experimental sensihvity not limited by theory errors τ = the heaviest lepton in the 3 rd gen. [ m= ±0.17 MeV/c 2, τ=(290.6±1.0)x10-15 s ] And, SensiHve to New Physics Lepton Flavor Viola2on CP violahon, EDM, lepton universality γ χ% 0 τ τ% µ%% () e µ () e (m ) 2 l% 23(13) τ µ h µ () s µ ( s )

13 Lepton Flavor Violation Quarks have flavor mixing. Neutrino mixing has been found. What about charged leptons? ν ν e µ?? ντ e µ τ (Original figure by Dr. Kuno / Osaka Univ.) γ χ% 0 τ τ% µ%% () e µ () e (m ) 2 l% 23(13) τ decays probe mixings between 3 2 and 3 1 generations. B factory is also a tau factory 13

14 Role of LFV in τ decays In case of SUSY, LFV processes are induced by offdiagonal elements of the slepton mass matrix. Sensitive to the SUSY breaking mechanism Diagonal elements by LHC & g-2, EDM Slepton mass matrix ( 2 ) l% m = ij 2 m 11 2 m 21 2 m 31 Muon LFV (µ eγ, µ e conv.) 2 m 12 2 m 22 2 m 32 2 m 13 2 m 23 2 m 33 Tau LFV processes τ eγ τ µγ qi q% q% i j (m ) 2 q% 23(13) q j & more decay modes. LFV in τ decays probes NP flavor mixing bet. 3 1, 3 2 generations.

15 LFV in τ decays with NP τ µ γ γ W% χ τ µ () e ν ν% ν ν% τ µ In SM, negligibly small even including neutrino oscillation α * Δmli Br ( τ µγ) Uτ i U µ i 2 32π i = 1, 2 m w = < 10 U Δ = : MNS neutrino mixing matrix m m m ij νi νj :Neutrino mass square difference 54 Example: SUSY + Seasaw (J.Hisano et. al., PRD60 (1999) ) tan β 1TeV Br( τ µγ) ; msusy Br(τ µγ)=o(10-7~9 ) Many extensions of the SM predict LFV decays. Their branching fractions are enhanced as high as current and near future experimental sensitivity. LFV is a clear signature of NP, if observed.

16 LFV in Higgs mediated model τ 3, l lη h µ () e µ ( e) or q q η, τ µ () e These decays become important when sleptons are much heavier than weak scale τ 3µ (A.Brignole, A.Rossi, PLB 566 (2003) 217) τ µη (M.Sher, PRD 66 (2002) ) τ µη may be enhanced. Br( τ µη): Br( τ 3 µ ): Br( τ µγ) : 8.4:1:1.5

17 NP signature in τ lγ, lll The two decays have different sensitivity for different NP models. % χ τ µ () e ν% ν% µ τ γ h µ () e µ ( e) τ µ () e Reference τ µγ τ µµµ SM + heavy Maj ν R PRD 66(2002) Non-universal Z PLB 547(2002)252 SUSY SO(10) PRD 68(2003) msugra+seesaw PRD 66(2002) SUSY Higgs PLB 566(2003)217 Searches in various LFV modes help to discriminate NP models.

18 SUSY-GUT Goto, Okada, Shindou & Tanaka PRD77, (2008) SU(5)+ν R, non- degenerate ν R (I), normal Hierarchy MEG search region for µ eγ If MEG find µ eγ at ~10-13, good chance to see also τ µγ at Even if MEG does not, still important to search for τ µγ.

19 Muon g-2 & τ µγ 3.4 σ discrepancy found in the muon g- 2. δa = a a = (27.6 ± 8.1) 10 NP exp SM 10 µ µ µ CorrelaHon to τ µγ Their diagrams are similar except for the flavor mixing. Fix the mass scale NP 2 δ a 8 µ θ τµ γ 9 2 BR( τ µ )~10 SUSY + Seasaw g-2 τ µγ By Tobe-san at B physics WS in Hakone (Nov.2008)

20 Experiments LFV is forbidden in SM, therefore, very clear NP signal. Appearance is also very clear. IdenHfied as a peak in M inv. ConsideraHons; StaHsHcs Background ResoluHon

21 Statistics Much more at Super-KEKB! B- factory provides unprecedented large sample of τ leptons. B-factory is τ-factory! History of τ µγ Search Facility # τ CLEO 10 7 BES- III 10 8 B- factory 10 9 Super B factory Super tau-charm (BINP) : a few x (10 35 cm -2 s -1 ) (Super) B factories dominate the results

22 τ µγ, eγ 535 fb -1 τ µγ τ eγ PLB666, 16(2008) Δ eγ Br<4.5x10-8 at 90%C.L. Br<1.2x10-7 at 90%C.L. Background: τ µνν/eνν + ISR (or beam background) Small amount of µµ events in ΔE>0

23 τ µγ background Background components τ+τ- Removed by missing mass vs P miss. Initial state radiation µ m γ µ ISR m ν e + e - τ + τ - γ / e + e - µ + µ - γ µνν ΔE<0 Removed by requiring not µ for the tag side. 15% of BG ΔE>0 signal data

24 τ 3leptons from Belle Data: 782t - 1 Prev.: 543t - 1 No event is found in the signal region. Dominant BG; Bhabha e + e - e + e - µ + µ - B<( )x10-8 Improved from ( ) 1 The most stringent upper limits among LFV τ decays Still a few background Will be improved by 1/L int EPS2009,Preliminary] τ e - e + e - τ µ - µ + µ - τ e - µ + µ - τ µ - e + e - τ e + µ - µ - τ µ + e - e - Mode ε (%) N EXP BG σ syst (%) UL (x10-8 ) e e + e µ µ + µ e µ + µ µ e + e µ e + µ e µ + e

25 τ lη,lη,lπ 0 Signal MC data τ µ + η,η,π 401fb -1 (PLB648, 341 (2007)) Br(τ lη,lη,lπ 0 ) <(6.5-16)x %C.L. τ η/η / π 0 Eff(%) N(exp) N(obs) N UL (90%CL) Br UL (90%CL) Combined µη π + π - π γγ eη π + π - π γγ µh π+π- η ργ eh π+π- η ργ µπ 0 γγ eπ 0 γγ Only a few background Will be improved by 1/L int

26 τ lll: Background suppression Signal topology BG events Bhabha(µµ) eeµµ(eeee) electron-veto on the tag-side (e-e+e- and e-µ+µ-) γ-conversion veto (e-e+e- and µ-e+e-) m 2 miss and p miss (e-e+e-, µ-µ+µ-, e-µ+µ-, µ-e+e-) mode µ µ + µ e - e + e - µ e + e - Dominant bkg. ττ qq µµµµ Bhabha eeee ττ e µ + µ eeµµ ττ µµ µ + e e e + µ µ ττ qq

27 LFV results 3leptons lγ lk s lhh lf lv 0 0-8

28 Constraints on New Physics Constraints depend on NP models. Examples to illustrate the sensihvity MSSM w/ seesaw 1TeV Br( ) msusy 6 2 τ µγ = 1 tan β Higgs- mediated model 4 PRD60, (1998) 7 tan β 100GeV Br( τ µη) = ma 6 PRD66, (2002) 4 β τ µγ % % Useful information are being obtained. " " " %

29 Future Prospects LFV sensihvity depends on the background level. T lγ Sensitivity is currently limited due to background from ττγ (ISR). Sensitivity dependence on luminosity 1 L T 3l, l+m Negligible background at 1ab -1. A few BG events at 10ab -1. Good PID Mass restriction to select mesons. 1 L

30 Future prospects Super B- factory: L int = 10 50ab - 1 N τ = (1 5) x τ µγ τ µη τ lll Recent improvement in the analysis BG understanding Intelligent selechon 1 L Extrapolation based on early analyses. At 50 ab - 1 Br(τ µγ) < O(10-9 ) Br(τ lll) < O(10-10 ) Extrapolation based on improved analyses. Good chance to see NP!

31 ττγ BG events in τ µγ analysis If we can remove BG events caused by ISR completely 1.5 ab -1 generic ττ MC removed by generator info. 90% events removed! When we run an accelerator with lower energy than Υ(4S), Can we reduce these ISR BG events?

32 Low energy running OperaHon near ττ threshold for τ µγ search Advantage Larger cross sechon max. at s = 4.25 GeV σ(ττ) ~3.6nb ( x 4 wrt 4S ) DramaHc reduchon of ττγ background Eγ from ττγ is low, and separated from the signal region. Eγ (CMS) from τ µγ and ISR(ττγ) s=10.58gev s=4.25gev s=5.0gev s=4.0gev

33 Cont d Disadvantage Lower luminosity? Higher µµγ background σ(ττ) ~3.6nb ( x 4 wrt 4S) σ(µµ)~6.4nb ( x 6.2 wrt 4S) What about for τ 3µ Need more studies TAU06 Machine running near threshold w/ L > cm -2 s -1 would be interesting! cf: Super Tau-Charm (BINP), INFN Super-B L = cm -2 s -1 near threshold.

34 Layout of injection using VEPP-5 Charm/τ - Factory Double ring VEPP-4M VEPP-2000 VEPP-5 BEP VEPP-3 Synchrotron 2.5 GeV The active R&D and civil construction efforts in the Institute are aimed to the Tau/Charm Factory with luminosity cm -2 s-1 and longitudinal polarization. 34

35 Summary Super- B is also a Super Charm factory: D- D mixing, CPV at sensihvity of O(10-3 ). Crucial tools for super- precise CKM. ExoHc hadrons. Super- B is also a Super Tau factory: LFV search at O(10-9 ) O(10-10 ) Will become more & more important. Especially when signals found at MEG, LHC Not limited by theory (hadronic uncertainty) We must be ready for some ophons to maximize physics outputs.

36 Summary LFV is one of the front runners to find NP. If found, new paradigm of parhcle physics research Tau provide rich physics programs there! Plan of Super- KEKB LHC MEG Direct search Br(µ eγ) PRC µ e conv Super- KEKB τ lγ, lll, lη, ( 40 modes) The real Super-tau? L int (ab - 1 ) ~x10 9 τ τ Now 3- yr shutdown for upgrade τ lγ :Ο(10-9 ), τ lll :O(10-10 ), Low energy run? Pol. beam?

37 Backup

38 D-D mixing in SM

39 Prospect at Belle II EsHmated by B. Golob StaHsHcal error scaled w/ L SystemaHc error Scale component ex: RaHo of DCS/CF improved w/ L Non- scale component ex: Model dependence, Detector resoluhon limit 1) CP eigen state: D KK/ππ 2) WS decay: D Kπ

40

41 XYZ found at B-factories Tetraquark u c c u D (*) D (*) Molecule π c c u u Hybrid c c g g 41

42 SUSY-GUT Hisano, Nagai, Paradisi & Shimizu arxiv: SU(5)+ν R µ eγ depends strongly on U e3, but τ µγ does not at all. m M 2 2 (3 m + A ) 3 L ij π H u * ν3 ( m %) ; UU i3 j Close to the current experimental limit If U e3 is tiny, τ µγ still within the Super B factories reach, while µ eγ could be too small to be seen by MEG.

43 LFV analysis Signal side: τ decay of interest Tag side: τ 1 trk w/ n γ + missing 1-prong decays occupy >80% of the τ decay. Loose constraint on ν based on P miss, M 2 miss. Background ττ, continuum (qq), µµ, ee, Particle ID Signal evaluation based on M inv ~ Mτ & ΔE ~ 0 ΔE=E rec -E beam Signal region is open after analysis cuts are finalized. Signal region Background Signal MC M inv

44 LFV τ decays; Signal and Background e + e - τ + τ 1 prong tau decay (BR~85%) ττ π π + π ν photon process f=leptons,quarks signal ν Both sides have neutrino(s). qq radiative Bhabha process e + e e γ e + e Only tag side has neutrino(s). many tracks e +

45 LFV results Belle BaBar UL (x10-8 ) Lum(N - 1 ) UL (x10-8 ) Lum(N - 1 ) τ µγ τ eγ τ µη τ eη τ µπ τ eπ τ µη τ eη τ µµµ τ eµµ τ µee τ eee τ µeµ τ eµe τ µρ τ eρ τ µk* τ ek* τ µk* τ ek* τ µφ τ eφ τ µω τ eω No signal yet! Too bad! Belle BaBar UL (x10-8 ) Lum(N - 1 ) UL (x10-8 ) Lum(N - 1 ) τ µks τ eks τ µksks τ eksks τ µππ τ eππ τ µkπ τ ekπ τ µπk τ eπk τ µkk τ ekk τ πµπ τ πeπ τ πµk τ πek τ KµK τ KeK τ µf τ ef τ Λπ τ Λπ τ ΛΚ τ ΛΚ

46 What about polarized beam? Longitudinally polarized beams help to reduce the ISR background. (ISR emission flips the spin of e+/- beam) Only one beam (electron) DistribuHon of BKG shi ed away from signal. But, effect is not so significant? Both two beams ττγ events are inhibited. dramahc suppression of BKG Require polarized e+ beam R&D for ILC (synergy!) Only 10% improvement in UL? T. Omori et al., NIMA500, 232 (2003) arxiv: (study by INFN Super-B) After discovery of LFV, pol. beam is useful to investigate helicity nature of NP. In any case, need polarized beams without loosing L!

47 Polarized beam Italian SuperB option Tau EDM, g-2 Search for CP/T violation in tau decays Search for LFV BG reduction LFV signature Physics structure

48 How to measure EDM, g-2 EDM Estimate tau spin direction from decay angles Momentum correlation

49 Tau EDM Belle (30fb -1 ) Polarized beam (P-odd) Another correlation can be utilized. Sensitivity improve by a factor of 4~5. G.A.Gonzalez-Sprinberg, arxiv:

50 Tau g-2 Muon g-2 O(10-9 ) shift M. Davier et al., arxiv: ~ m 2 Tau g-2 O(10-6 ) shift Current limit by Delphi (e+e- e+e-τ+τ )