Physical Program of Tau-charm FactoryV.P.Druzhinin,Budker INP, Novosibirsk

Processes at tau-charm factory)μμeσ(e

hadrons)eσ(eR

DD DD ss DD

ss DD cc

cc

D Ds

Main topics

Physics of charmonia Light hadron spectroscopy Open charm hadrons Physics of -lepton

Current and future experiments

CLEO-C BES-III/ year

-charm/year

J/ 10109

100(2S) 54 pb-1 27106 3109

(3770)

818 pb-1

5106 D-pair

3107

4.17 GeV

586 pb-1

7105 Ds-pair

2106

+ 4106 2107 B-Factories produced about 1010 charmed hadrons and 109 -pairs

CharmoniumVector states:J/ 1012

(2S) 1011

(3770) 2109

Higher ’s 108

In decays:c(1S), cJ 1010

hc 108 ((2S)hc0)

Comprehensive study of charmonium decays

Charmonium states above open charm threshold

Recently observed new charmonium states:

C+: X(3872), X(3940), Y(3940) , Z(3930)•cJ(2P),c(3S) ? Study of radiative decays of (4040), (4160), (4415).•Search for hadronic transition X,Y,Z

1--: X(4260),Y(4361),Y(4664) •(e+e- X)50 pb. •Scan of energy region 3.8-5 GeV with integrated luminosity 100 fb-1

Rare J/ decayNumber of J/’s 1012

Weak decays: J/Ds(*)l, Ds

*+-, Ds+ B(3-4)10-9

SM for S=0 weak decays: J/D00, D00 B10-11. Probe for New Physics, FCNC cu transition. ccss transition with W exchange: C-parity violation decay J/, B10-8

Search for NP in Lepton Flavor Violation decays J/l+l B(--e+e- ) < 2.7 10-8 (5108 pairs) B(J/+-)< (2-6)10-9

o CP-violation in J/ decays: 3 and more body decays to construct CP-odd observables or 2 body decays with polarization measurement, J/.

Light meson spectroscopy

• Low-lying charmonium states decay into light hadrons with relatively small multiplicity• Choosing specific cc-meson decay mode one can study states with practically any quantum numbers• Example: B(J/)=0.5% 5109 tagged mesons. Recently CLEO performed precise measurement of mass and observed decay 3.• Search for glueballs (gg) and hybrids (qqg)

Search for glueballs and hybrids

oLattice QCD predicts glueball spectrumo Glueball states mix with ordinary mesonsoDetailed study of the meson properties in different reactions and decay modes

Scalar glueball (f0,a0,K0*)

family• J/f0,f0,f0,a0, K*K0

*

• f0,a0

• For decays into PP,VP,VV,V

Lowest mass hybrid meson has exotic quantum numbers 1-+ Its mass is expected in the range 1.3-2.2 GeVTwo possible candidates 1(1400), 1(1600) in N1

N reactionS-wave decay c11, P-wave decay J/1

D-mesons Three types of D-mesons:D (cd), D0 (du), Ds

(ds)

Maximum cross section for D-pair production

DJ states can be produced in reactions e+eD(*)DJ

with 1 nb (4.3-5 GeV) Tau-charm factory can produce 6109 D-pairs and 109 Ds pairs per year. B-factories 1010 charmed hadrons

Advantages of near threshold production

• Particle multiplicity at 3.77 GeV is about two times lower than at 10.6 GeV• Two body production e+e-DD. This allows to use double tag method:

• fully reconstruct one D • then either fully reconstruct the other D (absolute branching ratios)• or look for events with one missing particle (leptonic, semileptonic decays)

• Coherent production of D pairs allows to use quantum correlations for D-meson mixing and CP violation studies

Leptonic and semileptonic decays Measurement decay constants and form factors.

Improve understanding of hadronization mechanisms. Validation of lattice QCD.

With improved theoretical input determination Vcs and Vcd.Important for B-physics extracting Vub from semileptonic B decay.

Current lattice values:fD=2074 MeVfDs=2413 MeV

Experiment (CLEO):fD=2069 MeVfDs=2708 MeV

Tau-charm factory can provide measurement of the decay constants with accuracy better than 0.5%.

Semileptonic decays

o.5% accuracy of BF 106 events

D-mixing at tau-charm factory•Only time integrated measurements•Study of quantum correlations in e+e-D0D0(0) (C-odd) and e+e-D0D*0D0D0 (C-even)

)])(([

)])(([

)])(([

)])(([00

00

00

00

,

eKeKDDN

eKeKDDN

KKDDN

KKDDN

At (3770) RM=(x2+y2)/2 can be measured using the ratios

For 109 D-pairs about 150 events will be detected. Sensitivity to RM is about 510-6

D-mixing at C-tau factoryProbabilities of inclusive decays are proportional to (1 y). S+ or S- are CP-even or CP-odd final states.

XSDD 00

);();();();(

);();();();(

41

SXSl

SXSlSXSlSXSly

For 109 D-pairs sensitivity for y is about 810-4

Fit of the inclusive and exclusive rates for decays of DDbar system into different final states allows to determine x, y, rf and f . Expected sensitivity to mixing parameters: 1 ab-1 at tau-charm factory = 10 ab-1 at Super B-factory

Search for CP-violationDirect CP violation in D decays is expected to be small in SM.

For CF and DCS decays direct CP violation requires New Physics.Exception: DKS,L with ACP=3.310-3.

For Singly Cabibbo Suppressed (SCS) decays SM CPV could reach 10-3.

)()(

)()(

fDfD

fDfDCPA

Best limits:

Belle: D0K+K-,+-

ACP(K+K-)=(0.430.300.11)%ACP(+-)=(0.430.520.12)%

CLEO: D+KS+, KS+0

ACP(KS+)=(-0.61.00.3)%ACP(KS+0)=(0.30.90.3)%

At Tau-charm factory CP asymmetry can be tested with 10-3 sensitivity for many final states.

Search for CP-violation

CV violation in mixing:

With 109 D-pairs about 30 (K+e-)(K+e-) events will be detected.|q/p| can be measured with 6% accuracy. Current value is 0.860.16

Use of quantum correlations:At (3770) : f1 and f2 are CP eigenstates of the same CP-parity.The decay D0D0f1f2 is forbidden by CP-invariance. The rate is proportional to difference CP-breaking parameters for f1 and f2. 109 D pairs 10-3 difference between +- and K+K- final states. Similar approach can be used for final states with different CP-parities ine+e- D0Do reaction.

Search for CP-violation

For C-odd D0D0 state CPV in mixing does not contribute to asymmetry, for C-even state it contributes with twice intensity.

For multibody final states the analysis of Dalitz plots and T-odd moments distribution can increase sensitivity to CPV effects.

Tau-charm factory can provide 10-3

sensitivity for CPV in D-decays

Using quantum correlations allows to separate contributions from direct CPV and CPV in mixing

Rare D decay•Flavor Changing Neutral Current (cu l+l-)

•D0+- SM ~10-12 NP - 10-6 • CDF B< 4.310-7

•DXul+l- SM ~10-6 NP - 10-6 •D0 B(D+++-)< 3.910-6

•CLEO B(D++e+e-)< 7.410-6

•Lepton Flavor Violation NP - 10-6

•BABAR B(D0 +e-) <0.81 10-6

•BABAR B(D++e+-) <1.1 10-5

C-tau factory can provide 10-8 sensitivity

Rare D decay

SM: short distance B(cull)~10-8 long distance

B(Dll )10-6

New physics can introduce new particles into loop B10-6

-physics

•1010 -pairs ▫B-factories 109

▫Super-B ~ 51010

•Special run near threshold▫2E=3.55 GeV, =0.1 nb, N=108

▫’s are produced at rest kinematic constraint for hadronic decay very clean data sample

▫Non- background measured below threshold

Physical goals•High precision measurement BF and

structure function for hadronic decays▫e///K lepton universality▫s

▫ms,Vus

•Study of Lorentz structure of leptonic decay▫Lepton energy spectrum 4 Michel

parameters, two depend on polarization Polarized initial beam Measured via decay of second :

LFV decaysSuper-B, 75 ab-1

71010 -pairs • decay •Current best limit:

4.510-8 by Belle with 5108

•At Y(4S): ISR background from e+e-+-Upper Limit 1/L

• tau-charm factory with 1010 has similar or better sensitivity

Search of CP-violation in decays • CP-violation new physics, charged Higgs• Two amplitudes with different weak and strong phases • -KS-, ACP=310-3

• -K-0• Observables

▫ Rate asymmetry: (+f+)-(-f)~sin sin▫ Modified rate asymmetry ~sin sin▫ Triple product asymmetry (p1p2)~cos sin

• For complete description of matrix element , polarization and direction of should be known▫ Threshold production – low statistics▫ Polarization may increase sensitivity by several times

Polarization

•Michel parameters•CP-violation in -decays

▫Increase sensitivity by several times ?▫Decrease luminosity ?

Tau-charm physics

CharmoniaSpectroscopy, BFsLight hadron spectroscopyJ/ rare decays…

CharmSpectroscopy(Semi)leptonic decaysRare decaysMixingCP violaton…

TauSpectral functions, BFsLorentz structureCP violationLFV decays…

Charm baryonsBFsSemileptonic decays…