Haibo Li, IHEP, BES collaboration1 Charm Physics Results at BES and Prospects at BESIII Haibo Li On behalf of BES Collaboration Institute of High Energy Physics International Workshop e + e  Collisions from  to  February 27 - March 2, 2006, Budker Institute of Nuclear Physics, Novosibirsk, Russia BESIII is successor of the previous successful BES.

Haibo Li, IHEP, BES collaboration2 Open Charm Production at BES Experiments e + e  machines E CM =3770MeV #D 0 D 0 bar#D+D-#D+D- Mark III 9.6 pb  3.5   10 4 BESII33 pb  0.12   10 6 CLEO-c(goal)3 fb  10.8   10 6 BES III(goal)20fb  72   10 6 Tag one D meson in a selected tag mode. Study decays of other D, (signal D) 22% tagging efficiency Y(4S) for B) Charm Mixing, DCS, and cos  impact naïve interpretation of branching fraction analysis extension of Phys.Lett.B508:37-43,2001 hep-ph/ Gronau/Grossman/Rosner & hep-ph/ Atwood/Petrov See Asner & Sun, hep-ph/ Absolute Charm Branching fractions BESII had small sample of DD

Haibo Li, IHEP, BES collaboration3 BESII Detector VC:  xy = 100  m TOF:  T = 180 ps  counter:  r  = 3 cm MDC :  xy = 220  m BSC:  E/  E= 22 %  z = 5.5 cm  dE/dx = 8.5 %   = 7.9 mr B field: 0.4 T  p/p=1.7%  (1+p 2 )  z = 3.1 cm

Haibo Li, IHEP, BES collaboration4 D Signal Reconstruction In  (3770) rest frame: e-e- e+e+ Υ(4S) D D e-e- e+e+ ∆E∆E M ES

Haibo Li, IHEP, BES collaboration5 Single Tag D at BESII Total 9 modes BESII 33 pb  1 Single Tag D

Haibo Li, IHEP, BES collaboration6 Exclusive Semileptonic BF e+e+ W+W+ Reconstruct one hadronic D tag. Reconstruct a semileptonic signal candidate from the remaining tracks/showers. Fit kinematic variable Umiss ( = E miss – |P miss | ) for the missing neutrino of the signal. Latest LQCD, PRL 94, (2005) Decay rate for D  P V cq D P, V Analysis Techniques Fit to Umiss Fit to M BC LQCD : shape & rate correct: precision~10%

Haibo Li, IHEP, BES collaboration7 Absolute Semileptonic Branching fractions at BESII Decay ModesBR (%) BESII (33 pb  1 ) BR (%) PDG 3.82  0.40    0.60    0.13    0.31   1.39    1.04    1.59    2.30    1.19    0.75   0.8 BESII 33 pb  1 PLB (2005) PLB (2005) The Yellow region are preliminary results = For extractions of ratios of Vcd/Vcs and form factors : Isospin test – Puzzle in PDG 1.4  0.2

Haibo Li, IHEP, BES collaboration8 Ratio of the D->K*e and D->Ke test of HQET World average: LQCD, Quark model predict: 0.9 – 1.2 by Wirbel 1985, Isgur 1989,Bernad 1991 New prediction: ISGW2 model with a small axial form factor give a small BR(K*e ) :  0.54 BESII 33pb  1 Preliminary:

Haibo Li, IHEP, BES collaboration9 Search for D +   l + v,  + at BESII 33pb  1, BESII preliminary submitted to EPJc m(K+K-) Tagged D mass D+ +D+ + D+KD+K

Haibo Li, IHEP, BES collaboration10 f D+ from Absolute Br(D +     at BESII Tag D fully reconstructed A  from another D, Compute missing mass 2 : peaks at 0 for signal CLEO-c PRL, (2005 ) BESII PLB610,183(2005) S=3 B=0.33 BESII

Haibo Li, IHEP, BES collaboration11 Measurements of the Cross  (  +   )= 5.4 nb at 4 GeV R (units of  (  +   )) Unique event properties –Only DD not DDx produced –Can get D o D o, D + D -, D s D s BESII 33 pb –1, double tag Nucl. Phys. B (2005): BESII single Tag: PLB 603(2004)130 CLEO-c 56pb  1 : DT, PRL 95, (2005 ): The double tag results are dominated by statistic error !

Haibo Li, IHEP, BES collaboration12 Rare decays from BESII modeSignalEfficiencyUpper limitsPDG (2004 K 0 e + e  02.64% 5.7  10  1.1  10   e+e e+e 00.64% 2.4  10  5.2  10  e+ee+e 04.32% 3.5  10  1.0  10  K* 0 e + e  12.06% 1.3  10  4.7  10  Ke+eKe+e 09.64% 2.5  10  1.2  10  K+e+eK+e+e 09.20% 2.6  10  2.0  10  e+e e+e % 2.4  10  9.6  10  e+e e+e % 4.1  10  5.2  10  K  e + e  00.40% 6.2  10  N/A K *+ e + e  00.39% 6.3  10  N/A LFV processes BESII: 33pb  33pb -1 at BESII The signal region is clean! experimentally, it is easy.

Haibo Li, IHEP, BES collaboration13 Single D production in huge J/  Decays at BESII 58 millions J/  at BESII BESII preliminary results First look in J/  in the world! J/  weak decays Background level is small! m Ds mD-mD- m D0

Haibo Li, IHEP, BES collaboration14 Magnet: 1 T Super conducting MDC: small cell & He gas  xy =130  m s p /p = dE/dx=6% TOF:  T = 100 ps Barrel 110 ps Endcap Muon ID: 9 layer RPC EMCAL: CsI crystal  E/E = GeV  z = 0.6 cm/  E Trigger: Tracks & Showers Pipelined; Latency = 6.4  s Data Acquisition: Event rate = 3 kHz Thruput ~ 50 MB/s BESIII Detector The detector is hermetic for neutral and charged particle with excellent resolution,PID, and large coverage. Two rings, 93 bunches: Luminosity cm  s 6  cm  s 6  cm  s 2.1GeV

Haibo Li, IHEP, BES collaboration15 ResonanceMass(GeV) CMS Peak Lum. (10 33 cm -2 s -1 ) Physics Cross Section (nb) Nevents/yr J/   10 9   10 6  (2S)  10 9 D 0 D 0 bar  10 6 D+D-D+D  10 6 DsDs  10 6 DsDs  10 6 Average Lum: L = 0.5×Peak Lum.; One year data taking time: T = 10 7 s N event /year =  exp  L  T Charm Productions at BEPCII Huge J/  and  (2S) sample at BESIII; Note: in this talk, all R&D study are based on 4 years’ Lum. for D and Ds ( 20 fb -1 ) and one year’s Lum. for J/  (10 billion) and  (2S) (3.0 billion).

Haibo Li, IHEP, BES collaboration16 Absolute Charm Branching fractions at threshold at BESIII D + ->K - π + π + D 0 ->K - π + Single tags   (M BC ) ~ MeV, x2 with  0   (  E) ~ 7—10 MeV, x2 with  0 BES III MC K K vs K K Independent of L and cross Section in a double tags measurements Monte Carlo Double tags

Haibo Li, IHEP, BES collaboration17 Semileptonic decay and CKM Matrix at BESIII To find V cs & V cd need form factor from theory at one fixed q 2 point. Form factor term come from theory (Lattice QCD). Supposing ΔFF/FF ~3%, BESIII will get Well measured BESIII: Integrate Lumi. 20fb  DDbar MC simulation l D  l D   Vcd/Vcd 4%  Vcs/Vcs 11% BESIII  Vcd/Vcd 1.7%  Vcs/Vcs 1.6% l D  l D  Quark models, HQET, Lattice & other methods have all been invoked to calculate form factor absolute normalizations. These calculations have been done mostly at q 2 =0 or q 2 =q 2 max. (i..e w=1, just like F in V cb in B  D * l ) Great contribution to CKM Unitarity

Haibo Li, IHEP, BES collaboration18 Precision of f D(s) at BESIII With 20fb   at BESIII 3 generation unitarity global fit: hep-ph/ CKMfitter group BESIII MC with 1 million Ds Challenge LQCD Prediction!

Haibo Li, IHEP, BES collaboration19 D Dalitz Plot method – input to  3 /γ: B -  DK -, D  K s     limited by uncertainty due to Dalitz plot model currently – Extract strong phase and study CP violation by using CP tag. – Study light scalar in Dalitz D decays  S-waves in D +   m 2 (  S  ) RS (GeV 2 ) m 2 (     ) (GeV 2 ) CLEO II.V - D 0  K S  +   CP+ f 0 (980) CP-  (770) As Alex Bondar pointed out, CP tagged D  K S   can be 10K in 10fb -1  (3770) sample at BESIII, it will give a uncertainty below 2 0 on  3 /γ ! But note that the D 0  K S  is dominated by  and K*  which are longitudinally polarized. The most interesting events are accumulated near the corner of the Dalitz, which have very soft Ks or pion, this effect may affect the real efficiency on the DP, especially, have very low efficiency near the kinematic limit of DP. We have to do MC simulation to test it at BESIII?? K*(892) - A. Bondar et. al hep-ph/

Haibo Li, IHEP, BES collaboration20 –cos  D ~  10% Measurement of Strong Phase Flavor mode I. Shipsey cos  D ~  2% at BESIII r D = 3.3  10 

Haibo Li, IHEP, BES collaboration21 Relative yield of charged and neutral D pairs at  (3770) the resonance region (1) From CLEO-c L = 55.8 pb  3770 MeV: Can phase space difference explain all the effect? If only phase space f = 0.69, which can not explain data! Two additional source sources: (1) Coulomb interaction between charged meson 1%—5% M. Voloshin hep-ph/ (2) Possible continuum contribution (EM process) Both above are EM process which may violate the isospin symmetry or violate the single iso-vector dominate. e+ e+ e-  (3770) * * * * Coulomb correction Yukawa correction Phys.Rev.Lett. 90, (2003)R. Kaiser et al.

Haibo Li, IHEP, BES collaboration22 Relative yield of charged and neutral D pairs at  (3770) the resonance region (2) It will be interesting to look at the ratio f vs E CM. A finer scan of the ratio of the cross sections will be very useful to test the prominent variation (1%-5%)in the vicinity of  (3770) peak at BESIII According to M. Voloshin model ( hep-ph/ ), one can get: Coulomb interaction between charged mesons Phase space difference f E CM hep-ph/ hep-ph/ M. Voloshin E CM is the central mass of energy; a is the distance parameters ;  =  BW +  1  1 is the phase for non-resonant scattering, and  BW is the y(3770) BW phase.

Haibo Li, IHEP, BES collaboration23 D Mixing shifts energy of CP eigenstates shifts lifetimes of CP eigenstates x mixing: Channel for New Physics. y (long-range) mixing: SM background. New physics will enhance x by entering the loop but not y.

Haibo Li, IHEP, BES collaboration24 BES III Charm Mixing Mixing:  (3770)  DD(C = -1) Coherence simplifies study DCSD interfere away so not a background Unmixed: D 0  K   + D 0  K +   mixing: D 0  K   + D 0  D 0  K   + Can add lepton final states (Klv Klv) Sensitivity: current limit: 10  r Mixing at BESIII K    vs K     in (K    )(K    ) ~1 background event is expected r D sensitivity is abut 1x10 C.L. K    vs K    Efficiency: 12.5% BESIII Monte Carlo Simulation

Haibo Li, IHEP, BES collaboration25 Direct CP Violation at ψ(3770) at BESIII    , K  K ,      s  0, CP violating asymmetries can be measured by searching for events with two CP odd or two CP even final states ex: A CP sensitivity is about 10 C.L. K K vs  Beam constraint Mass BESIII MC simulation Rss =(10.7  0.8)  10  BR(   KSKS)= (3.6  0.3)  10   be accessible at KLOE? It is also true in phi decay: hep-ph/

Haibo Li, IHEP, BES collaboration26 Rare & Forbidden D Decays: FCNC, LFV, LNV 3fb -1 Sensitivities 10  Focus hep-ex/ and G. Burdman PRD (2002) Observation of D + FCNC and lepton number violating decays could indicate new physics. CLEO-c hep-ex/ D. Miller 281pb -1 D +  V  + (V  e + e  ) are main backgrounds, , ,  Great improvement at BESIII with 20 fb-1, about 100 million DD pairs, but not competitive with 550 million DD pairs at B factory for rare decays The sensitivity will be at BESIII

Haibo Li, IHEP, BES collaboration27 Access to Semileptonic Weak Decay of J/  (1)   D S *+ l  R =     D S + l    D *+ l  R =     D + l  The rate of weak decay of J/  is at 10  8 level, and inclusive search at BESIII may be available: J/   D* + S X D* + S  D S +  (soft  )  D + S            K S K +   ……. Detail simulations are being done at BESIII. Z.Phys.C62: ,1994 M. Sanchis-Lozano More input from theorists ! Sun S.S et al at BESII are working on the above modes Based on 58 M J/  : The sensitivity at BESIII: 10  7 – 10  8 Semileptonic decays: based on heavy quark spin symmetry: Br (J/   Ds l ) = 0.26  10  8 ; Br (J/   Ds* l ) = 0.42  10  8 A model independent prediction for the ratio of the above BRs:

Haibo Li, IHEP, BES collaboration28 Access to Weak J/  Decay at BESIII (2) J/   PP ModeDecayBr(10  10 ) (  40% )  C =  S=+1 (c  s )  C=+1,  S=0 (c  d)   D S +      D 0 K 0   D S + K      D +       D 0    D 0  ’   D 0  J/   PV ModeDecayBr(10  10 ) (  40% )  C =  S=+1 (c  s)  C=+1,  S=0 (c  d)   D S +      D 0 K* 0   D S + K*      D +       D 0    D 0    D 0  hep-ph/ , K. Sharma We need more theoretical input!   D S *+    R =     D S +    They are too rare to be searched at BESIII (10 10 ) according to SM estimation. But sensitive to new physics if larger BRs measured. < J/   D S (D S *) M (M = , , ,  ’,K, K*,  )

Haibo Li, IHEP, BES collaboration29 Summary for BESIII Analysis review of BESIII Charm Physics at threshold at BESIII Absolute BRs, test of QCD Decay constants with double tags events f D+ : 1.5%; f Ds : 1.1% with 20 fb-1 data Form factors and Vcs and Vcd D mixing at threshold R mixing : 2.5  10  Direct CP violations: A CP : 10  The sensitivity of rare charm decay 10 , at B factories : 10  500 fb -1 data Measurement of Strong Phase cos  D ~  2% The start of data taking at BESIII promises an era of precise charm physics. This comes at a fortuitous time, recent breakthroughs in precision lattice QCD need detailed data to test against. Charm is provide that data. If the lattice passes the charm test it can be used with increased confidence by: BABAR/Belle/CDF/D0//LHC-b/ATLAS/CMS/BTeV to achieve precision determinations of the CKM matrix elements Vub, Vcb, Vts, and Vtd thereby maximizing the sensitivity of heavy quark flavor physics to physics beyond the Standard Model. BESIII will provide unique opportunity for open charm physics: Charm event produced at threshold are very clean with low multiplicity; Charm events at threshold are pure DD pairs; Double tag studies are pristine; Signal/Background is optimum at threshold; Neutrino reconstruction is clean; Quantum coherence

Haibo Li, IHEP, BES collaboration30 Thank you Спасибо

Haibo Li, IHEP, BES collaboration31 Back-up slides

Haibo Li, IHEP, BES collaboration32 Scan of the resonance 3.7  4.6 GeV Test isospin symmetry far away from open charm threshold! Since the EM effect may be significant far away from DD threshold! Could possible EM contribution affect the ratio? Interference effect : It will be very helpful to make a fine scan of the 3.7  4.6GeV, so that one can understand the formation of DD system near or above the threshold

Haibo Li, IHEP, BES collaboration33 Scan of the resonance 3.7  4.6 GeV(2) Test 3.7  4.6 GeV Search for exotic ccbar, Y(4260) Probe gluon enhanced hidden ccbar states

Haibo Li, IHEP, BES collaboration34 D meson Decay Constants Decay is forbidden as m l  0 : Helicity suppression Targeted near threshold at BES The uncertainty of Decay constants:

Haibo Li, IHEP, BES collaboration35 Challenge LQCD Prediction Expt/LQCD consistent at 45% CL Now: LQCD error ~8% CLEO-c error 8% CLEO <5% within a year Need latest LQCD predictions to few % by summer 2006 f D+ & 2007 f Ds (I. Shipsey )

Haibo Li, IHEP, BES collaboration36 Charm As a Probe of Physics Beyond the Standard Model CP asymmetry≤10  D 0 - D 0 mixing ≤10  Rare decays ≤10  High statistics instead of High Energy G. Burdman and I. Shipesy hep-ph/

Haibo Li, IHEP, BES collaboration37 Short distance SM Penguin, W box Short + long distance SM rho and phi  e+e- R parity violating SUSY B (D +   + e + e  ) ~ 2 x 10  In the SM Current experimental limit CLEO II: B (D +   + e + e  ) ~ 4.5 x 10 90%CL Goal observe, and one day study dilepton mass B (D +   + e + e  ) ~ 2.4 x R-parity violating SUSY : Increase in rate is small but significant at low dilepton mass In charm very difficult to calculate the SM rate for rare decays reliably. one of the most reliable: Burdman I. Shipsey

Haibo Li, IHEP, BES collaboration38 BES measured the branching fractions for inclusive non-DD-bar decays of  (3770) using two different data sample and two different methods . These are first measurements by using 33pb Determined from analysis of R values and DD-bar cross sections Obtained from fitting to the inclusive hadron and the DD-bar production cross sections simultaneously. Preliminary results of BRs of and

Haibo Li, IHEP, BES collaboration39 Compare B factories & Charm Factories CFactory 3 fb -1 BFactory 500 fb -1 PDG04 Statistics limited Systematics & Background limited % Error