Leptonic and semileptonic D decays

Transcription

1 Leptonic and semileptonic D decays Status and prospects at BESIII Hailong Ma (IHEP&BESIII) Joint BESIII-LHCb workshop in 2018 Feb , IHEP, Beijing 1

2 Main physics goals P or S 1. f D(s), f K(p) (0): better calibrate LQCD 2. V cs(d) : better test on CKM matrix unitarity U Vud Vcd Vus Vcs Vub Vcb 3. Test on lepton flavor universality (LFU) Vtd Vts Vtb 4. Search for new semileptonic decays 2

3 Samples of D 0() and D s at BESIII D 0() samples MARKI DELCO MARKII MARKIII BESII CLEOc BESIII D s samples 2011/ /4.14 GeV 4.17 GeV 4.009/ GeV e i NST 2 N B DD i ST i ST i ST i NDT 2 N B B B m sig N N tot ST D v DD tot DT y sig sig N i i i sig ( NST ST vs.sig / ST ) / i 1 N i 1 K π - D - π - i ST vs. sig N e - i ST 0 BES CLEOc BESIII 3

4 Single tag D 0() at BESIII e e - y(3770) D D - e e - y(3770) D 0 D 0 D - K p - p - D - K s p - D - K s K - D 0 K p - D 0 K p - p 0 D - K K - p - D - K p - p - p 0 D - p - p - p D 0 K p - p - p D - K s p - p 0 D- K p - p - p - p D - K s p - p - p D 0 K p - p - p p 0 D 0 K p - p 0 p 0 N -tag ( ) 10 D 6 largest tag modes give 1.5 M D - tags 4 N D ( ) 0 tag 3 largest tag modes give 2.3 M D 0 tags 10 4 Charge conjugations are included 4

5 Single tag D s at BESIII e e - D s D GeV e e - D s * D s- c.c.@4.178 GeV N -s D tag M ST D s- mesons 5

6 Measurement of D l v 818 pb -1 at y(3770) ( ) PRD78(2008) fb -1 data@3.773 GeV PRD89(2014)051104R BESIII result has been re-calculated with the latest LQCD calculation K L p 150 m vt v CLEO BESIII B D mn ( ) 10-4 B D mn ( ) 10-4 f D = MeV f D ( ) MeV V cd fb -1 data help to reduce the uncertainty of f D to 1% 6

7 Search for D t v 4s B[D t n] ( stat. ) 10-3 SM prediction: 2.66 BESIII: fb -1 data help to reduce the uncertainty to 8% 7

8 Previous measurements of D s l v In the past 30 years, D s l v has been studied by WA75, CLEOII, E653, BESI, L3, OPAL, ALPHA, CLEO-c, BELLE, Babar D s * D s-, 600 pb 4.17 GeV [697 l v] PRD79(2009) Belle, 913 fb -1 at GeV [2698 l v] Babar, 521 fb -1 at GeV [1023 l v] JHEP1309(2013)129 PRD82(2010) f Ds = MeV PRD79(2009) f Ds = MeV PRD80(2009) f Ds = MeV f Ds = MeV f Ds = MeV 8

9 Measurement of D s l v fb -1 GeV PRD94(2016) fb -1 GeV Use m counter to suppress background N[D s m v]= f Ds ( ) MeV f Ds V cs = MeV Uncertainty of f Ds with m/tv is expected to reach 1.5% with 3.19 fb -1 data 9

10 Previous measurements of D K(p)l v In the past 30 years, studies of D K(p)l v were made by MARKIII, E691, CLEO, CLEOII, BESII, FOCUS, BELLE, Babar and CLEO-c BELLE, 282 fb -1 at GeV Babar, 75 fb -1 at GeV PRD76(2007) D 0 K - e v PRL97(2006) Babar, fb -1 at GeV , CLEO-c, 818 pb -1 at y D 0 p - e v PRD91(2015) PRD80(2009) Before 2010, the LQCD calculated f D K(p) (0) precision is at 10% level, thus limiting V cs(d) measurement 10

11 Progress in LQCD calculations Taking from Aida X. EI-Khadra s talk at Beauty2014 9

12 Analysis of D 0 K(p) - e v B D K ( e v PRD92(2015) )% B ( D p e v )% Different parameterizations of form factor Single pole Modified pole ISGW2 Series expansion 12

13 Analysis of D K L e v PRD92(2015) Simultaneous fit to event density I(q 2 ) with 2-par. series Form Factor B(D K L e v) =( )% A CP D KLev =( )% D K L ev is measured for the first time f K (0) V cs =

14 Analysis of D K(p) 0 e v PRD96(2017) B[ D 0 K e v ] ( )% B[ D 0 p e v] ( )

15 Comparisons of f D K(p) (0) 15

16 Measurements of V cs(d) Taken from PDG, and the SL method suffers about 2.4% error from LQCD 16

17 Test of LFU in D 0() pl v decays Evidence of LFV at 4s in (*) (*) B(B D tn ) R( D ) (*) B(B D ln ) B( D B( D p p 0( ) -(0) 0( ) R LU 0( ) -(0) B PDG16 : R 0 LU m v) ~ 0.97 e v) (~ 2.0s ) D 0 p - m v p 0 p p - K 0 p p - Other Evidence of LFV at 2.6s in FCNC decays B K m m - /K e e D p 0 m v p 0 p p 0 K 0 p p 0 Other LHCb, PRL113(2014) B[D 0 p - m v] = ( )% B[D p 0 m v] = ( )% 17

18 Observation of D Se v Explore the nontrivial internal structure of light hadron mesons, traditional qq states, tetra quark system. With chiral unitarity approach in the coupled channels, BF is predicted to be order of 5(6) 10-5 for D 0() decays Improve understanding of classification of light scalar mesons R=1(3) if traditional qq (tetra quark) system 18

19 Form factors of D Ve v 19

20 PWA of D K - p e v PRD94(2016) Fractions with >5s significance Model independent S-wave phase measurement Properties of different Kp (non-) resonant amplitudes q 2 dependent form factors in D K *0 (892)e v M V/A is expected to M D*(1-/) Model independent form factors 20

21 Study of D we v and search for D fe v PRD92(2015)071101(RC) D we v D fe v B[D we v]=( ) 10-3 B[D fe v]< at 90% C.L. Better precision or sensitivity Amplitude analysis of D we v is performed for the first time r V =V(0)/A 1 (0)= r 2 =A 2 (0)/A 1 (0)=

22 Studies of D s K (*)0 e v at GeV BESIII preliminary D s K 0 e n e N obs = BESIII preliminary D s K* 0 e n e N obs = Fit background via inclusive MC 3.2 fb -1 data@4.178 GeV Data M Dssideband B[D s K 0 e n e ] =( stat 0.14 syst ) 10-3 B[D s K* 0 e n e ]=( stat 0.12 syst ) 10-3 ( ) 10-3 [PDG17] ( ) 10-3 [PDG17] Four dimensional un-binned likelihood fit is performed. K* paramters are fixed Taking V CKMfitter cd as input r V = r 2 =

23 Summary With ~3/3 fb -1 data taken at 3.773/4.178 GeV by BESIII, the leptonic decay of D (s) l v and some semi-leptonic D decays, and improved measurements of V cs(d), decay constants, form factors have been obtained More results are expected in the near future D s t v, f Ds and V cs D s h ( ) e v, form factors and V cs D s K K - /p p - e v, form factors D 0 K - m v, f K(q 2 ) and V cs D K 1 (1270)e v D (s) 0() Xe v All Cabibbo-suppressed D 0() decays and D s decays are restricted by the limited data 23

24 Prospects at BESIII With 20/6 fb -1 data taken at 3.773/4.178 GeV, some elementary constants can be further improved Systematic error Statistical error ~3 fb -1 Expected with 20/6 fb -1 Df D /f D 0.9% 2.6% 0.5% Df Ds /f Ds 1.5% 1.5% ~1% Df D K /f D K 0.5% 0.4% 0.15% Df D p /f D p 0.7% 1.3% 0.5% V cs Ds lv 1.5% 1.5% ~1% V cs D0 K-ev 2.5%(2.4% LQCD ) 0.4% 0.15% V cd D mv 0.9% 2.6% ~1% V cd D0 p-ev 4.5%(4.4% LQCD ) 1.3% 0.5% Only D s m v is considered. The contribution of D s t v will be comparable or slightly better than D s m v Once LQCD uncertainties reach <1% level, the V cs(d) will be much improved More or improved measurements of form factors of semileptonic decays, containing scalar or axial-vector meson, which are now statistically limited 24

25 Thank you! 25

26 BEPCII collider Beam energy: GeV Optimum energy: 1.89 GeV Designed luminosity: cm -2 s -1 Data taken from: 2009 Achieved luminosity: cm -2 s -1 26

27 BESIII detector <70 ps endcap updated in

28 Improved BF for D K 0 m v With 6 dominant D - single tag EPJC76(2016)369 K 0 p p ±130 Simultaneous fits K 0 p 0 p ±33 Taking B[D 0 K - m v] and B[D K 0 e v] from the PDG as input [ D [ D [ D 0 [ D K K K - K m v] 0 0 m v] m v] 0 e v] Support isospin conservation in these two decays within errors Consistent with theory prediction 0.97 within error 28

29 Absolute BF for D K 0 e v via K 0 p 0 p 0 With 6 dominant D - single tag CPC40(2016) ±78 Taking t D, t D0, B[D 0 K - e v] and B[D K 0 e v] from the PDG as input [ D [ D 0 K K - 0 e e v] v] Agrees with isospin conservation within 1.2s 29

30 Measurements of BFs of D s h ( ) e v Benefit the understanding of the source of difference of inclusive decay rates of D 0() and D s Complementary information to understand h-h mixing 482 pb -1 data@4.009 GeV, PRD94(2016) CLEOII 95 CLEOc09 CLEOc15 30

31 Measurements of BFs of D s f/h ( ) m v 482 pb -1 data@4.009 GeV, PRD97(2018) fe v fm v The ratios of BFs hm v h m v [ Ds [ D s [ Ds [ D s fm v] fe v] hm v] he v] [ Ds [ D s h' m v] h' e v] BFs of semi-muonic decays are measured for the first time 31