ran chistov 051205

Slide1: 

Charmonium Production and New Particles at Belle OUTLINE: (1) Introduction (2) Charmonium production in pp,  and e+e- (3) Double charmonium production in e+e- at Belle (4) Recent results on new particles at Belle: (a) Update of X(3872)  J/ +- (b) Observation of e+e-  J/ X(3940) (c) Observation of Z(3930) in  fusion (5) Observation of Y(4260)  J/ +- at BaBar (6) Summary Ruslan Chistov (ITEP, Moscow) Physics of fundamental interactions: ITEP 60th anniversary

Introduction: 

Introduction In recent 3 years: Belle observed double charmonium production in e+e- and a number of charmonium or charmonium-like states: c(2S)K0sK , X(3872)J/ +- , Y(3940)J/ , X(3940)DD* , Z(3930)DD; CLEO confirmed c(2S)  K0sK  in  fusion and observed (2S) 0hc, hc   c ; BaBar confirmed double charmonium production, c(2S)  K0sK  in , X(3872) and observed e+e-ISR Y(4260)  J/ +- ; CDF and D0 confirmed X(3872). X(3872), Y(3940), Y(4260) have not been assigned yet to any cc states and charmonium production in different processes is not well understood. All these observations have renewed experimental and theoretical interest in spectroscopy, decays and production of charmonia.

Charmonium production in pp: 

Charmonium production in pp Perturbative QCD: the leading mechanism for high-pT production is c-quark fragmentation The measured cross-section 30 times larger (CDF-1995) Suggest new mechanism (g +gg) fragmentation + Color-octet: g  (cc)8   n gsoft well describes cross-section and pt spectrum (few free parameters in the theory) predicts poorly J/ and ’ polarization

Charmonium production in : 

Charmonium production in  CLEO and BaBar: Observation of  c and confirmation of c(2S) previously observed by Belle in B decays and double charmonium production M=3642.7 4.1 4.0 Mev/c2 =0.27 +0.07-0.06 0.04 Q2  M2(cc)res

Charmonium production in e+e-: 

Charmonium production in e+e- Production of charmonium was not predicted by theory, but first observed experimentally CLEO(1990): N = 15.2  4.6 J/ events above kinematical limit for B-decays (p>2.0 Gev/c) in (4S) data No significant signal in continuum and (5S) data  (mis)interpeted as direct (4S) J/ X decay Many exotic models to explain CLEO wrong interpretation… but in few years with new data CLEO has observed the signal in the continuum as well (eeJ/X)  2 pb

Theory:  continuum J/ production : 

Theory: continuum J/ production Color Singlet ee J/gg 1pb Cho-Leibovich PRD 53,150 (1996) Color Octet ee J/g Significant around endpoint of J/ spectrum 0.05-0.5pb Braaten-Chen, PRL 76, 730 (1996) Color singlet ee J/cc 0.05-0.1 pb Kiselev et al PLB 411, 150 (1994) Cho-Leibovich (1996) Baek (1998)

First observation of double charmonium production: 

First observation of double charmonium production Study recoil mass against J/: Mrecoil ((Ecms –EJ/)2 –PJ/2)½ In two body process ee J/X Mrecoil=MX In the data: find threshold around 2mc and peaks at c, c0, c’ masses (e+e-  J/c) B (c>2charged) =3378 pb (6.1) (more than 4 charged tracks are required in selection to suppress large QED contamination) Belle observed (e+e-→ J/c)  10  NRQCD Belle PRL 89, 142001 (2202)

Theory: double charmonium: 

Theory: double charmonium The calculatations are done for single virtual photon diagram. As C = -1,  J/ J/ final state is forbidden Another diagrams are proposed and estimated to have a comparable contribution into double charmonium final states (Bodwin-Lee-Braaten): (e+e-→J/J/ ) should be large in this case! R = J/c /~s2(mcv/Ebeam)6 (e+e-→ J/c) = 2.31.1 fb matrix elements are determined from J/ e+e-, c Bodwin-Braaten-Lee; confirmed by Liu-He-Chao, Brodsky-Ji-Lee

e+e-  J/(cc)res update: 

e+e-  J/(cc)res update Update with more than 3 times larger data sample: Verify recoil mass scale using e+e-  (2S) ISR, (2S)J/+- Compare Monte Carlo prediction with data fit result  Mrecoil bias < 3 MeV/c2 Phys. Rev. D70, 071102 (2204)

e+e-  J/(cc)res update: 

e+e-  J/(cc)res update Fit includes all known charmonium states: c, J/, c0, c1, c2, c’,(2S) Fit gives negative yields for J/, c1, c2 & (2S) – UL’s @90% CL are shown with dotted line J/J/ can not explain Belle vs theory disagreement Phys. Rev. D70, 071102 (2204)

e+e- → (2S)(cc)res: 

e+e- → (2S)(cc)res Similar analysis for Mrecoil ((2S)) spectrum The prod’n rates for e+e-->(2S)(cc)res are of the same magn as J/(cc)res Phys. Rev. D70, 071102 (2204)

e+e- → J/ open charm: 

e+e- → J/ open charm First clear and significant signals: Found D*+ and D0 accompanying J/ Based on LUND c D*+ and c D0 fragmentation rates calculated: (e+e- J/cc)/(e+e- J/X) =0.590.140.12 Perturbative QCD: (e+eJ/cc)/(e+e- J/gg)~0.1 Berezhnoy-Likhoded (2003) Some theoretical uncertainties is canceled out in the ratio

e+e- → J/ open charm: 

e+e- → J/ open charm Update: New analysis with reduced model dependence: Fit D(c) signals in Mℓℓ bins J/ yields:

(e+e- → J/ cc): 

(e+e- → J/ cc) All final charm hadrons are reconstructed (except for c)  do not need model to calculate cross-section Sum over D0,D+,Ds, c and (cc)res yields to extract the fraction of total prompt J/ production that is accompanied by another cc pair: (e+ e- J/ cc)/(e+ e- J/ X) = ( 0.5  (ND0 + ND+ + NDs + Nc ) + Ncc ) / NJ/ = 0.820.150.14 (e+ e- J/ X) was measured by Belle & BaBar to be 2pb  (e+ e- J/ cc) is factor of 10 larger than the NRQCD predictions (similar disagreement as for (e+ e- J/c) )

Confirmation of double cc production at BaBar: 

Confirmation of double cc production at BaBar BaBar

New charmonium or charmonium-like states : 

New charmonium or charmonium-like states Observation of X(3872) and Y(3940) - both are candidates for new types of hadrons: DD*-molecule and cc-gluon hybrid Observation of X(3940) - c(3S) candidate Observation of Z(3930) - ’c2 candidate Observation of Y(4260) - (4S) or cc-gluon hybrid candidate

X(3872): observation by Belle,confirmation by CDF, D0 and BaBAr: 

X(3872): observation by Belle, confirmation by CDF, D0 and BaBAr Belle: no DD mode disfavour 0+, 1-, 2+, ... M.B.Voloshin, L.B.Okun (1976) predicted a deuson

Belle: X(3872) update’2005: 

Belle: X(3872) update’2005 hep-ex/0505038 P(X)=+1

Evidence for  X(3872)  J/  at Belle: 

Evidence for X(3872)  J/  at Belle Look for B  J/K (c1J/ for calibration) Fit Mbc in bins of J/ invariant mass: Strong evidence for X  J/ decay: (XJ/)/(XJ/)=0.140.05 Theory expects for this ratio ~ 40 if X(3872)=c1’(23P1) and moreover, M (c1’) is predicted 100 MeV higher N=13.6+-4.4 events, 4 C(X(3872))=+1 All favour for JPC=1++ hep-ex/0505037

Other properties of X(3872) obtained at Belle and BaBar: 

Other properties of X(3872) obtained at Belle and BaBar hep-ex/0505038 Belle: many angular distributions were analyized  rule out 0++, 0-+ and favour for 1++ (J.L.Rosner, Phys. Rev. D 70, 094023 (2004)). Observation of X->J/  --> large isovector component in X(3872) w.f. BaBar: R=Br(B+->XK+) / Br(B0->XKs)=0.5+-0.3 Delta M = 2.7+-1.3 MeV hep-ex/0505038 Theoretical models: (1) DD*0 molecule bound by pion exchange; (Tornqvist (2004), Close and Page (2004), Swanson (2005), M.B.Voloshin (2004)) (2) diquark-antidiquark “tetraquark” state [cq] [cq] (Maiani et al. (2005))

Observation of Y(3940)  J/  at Belle: 

Observation of Y(3940)  J/  at Belle

2005: Observation of e+e-  J/ X(3940) at Belle: 

2005: Observation of e+e-  J/ X(3940) at Belle c c0 c’ X(3940) N=266+-63 5 Mass=3936+-14 MeV =39+-26 MeV hep-ex/0507019 Above DD(*) threshold

Decay modes of X(3940) : 

Decay modes of X(3940) Reconstruct only one D; Combine J/ and D; Look on recoil system against (J/ D) - tag J/ DD(*) events; Refit Mrecoil(DJ/) to nominal M(D*) or M(D); Improve Mrecoil(J/)  M(DD(*)) resolution by a factor ~2.5; Return to Mrecoil(J/)

Decay modes of X(3940) : 

Decay modes of X(3940) Additional search results in no evidence for X(3940)J/  mode X(3940) and Y(3940) have different widths and decay modes  they are different particles X(3940) could be c(3S) X(3940)DD*: N=24.5+-6.9 events; significance=5.0; Mass=3943+-6 MeV; =15.4+-10.1 MeV No evidence for X(3940)DD mode DD* No DD

2005: Observation of Z(3930)  DD at Belle: 

2005: Observation of Z(3930)  DD at Belle Mass =3931 +- 4 +- 2 MeV  = 20 +- 8 +- 3 MeV N = 41 +- 11 events significance = 5.5  hep-ex/0507033

Observation of Z(3930)  DD at Belle: 

Observation of Z(3930)  DD at Belle Masses of lightest states c0(2P) (’c0) and c2(2P) (’c2) are in the range of 3.9-4.0 GeV (above DD and around DD* thresholds) ’cJ -> DD should be dominant Is it the ’cJ ? (no radially excited cJ observed so far)

Observation of Z(3930)  DD at Belle: 

Observation of Z(3930)  DD at Belle Helicity distributions favour for 2++ , i.e. ’c2 candidate (angle btw D and beam axis in the  c.m. frame: *) J=2 J=0 2/ndf=7.3/9 2/ndf=32.2/9

2005: Observation of Y(4260)  J/ +- at BaBar: 

2005: Observation of Y(4260)  J/ +- at BaBar BaBar investigated e+e-  ISR J/ + - process: look for invariant mass of J/ + - combinations look for recoil mass against J/ + - hep-ex/0506081 N =125 +- 23 events Mass =4259+-8+2-6 MeV  =88+-23+6-4 MeV significance > 8

Observation of Y(4260)  J/ +- at BaBar: 

Observation of Y(4260)  J/ +- at BaBar BaBar claimed the evidence for the Y(4260) production also in B decays: B+  Y(4260) K+ What is the Y(4260) ? Another candidate for cc-gluon hybrid ? hep-ex/0507090 Mass is high - as predicted by lattice calculations. Above DD(*) thr but found in another mode. Or just (4S) ?

Summary: 

Summary Charmonium Production: Double charmonium production in e+e- is confirmed and few ideas to explain large discrepancy are ruled out – still a mystery for theory; e+e-  J/ cc production is measured with reduced model dependence; Belle

Summary: 

Summary New Charmonium-like Particles: X(3872) - well establ’d but no good cc candidate; a lot of information obtained - probably 1-- Y(3940) - misterious state above the DD(*) threshold but found in J/  X(3940) - not decaying into DD, but DD* Z(3930) - found in DD mode, properties are consistent with being a 2++ state Y(4260) - 1-- state found in J/ +- mode Belle BaBar

KEKB asymmetric e+e- collider: 

KEKB asymmetric e+e- collider Two separate rings e+ : 3.5GeV e- : 8.0GeV Crossing angle 22mrad Ecm : 10.58GeV c  200m Beam size: x = 100m y = 3m Luminosity: design: 1.0x1034 cm-2s-1 achieved: 1.07x1034 cm-2s-1

KEKB/Belle luminosity summary: 

KEKB/Belle luminosity summary May 1999- December 2003: accumulated: 179 /fb analyzed: 158 /fb KEKB records on the luminosity peak: 10.7×1033/cm2/sec World record per day: 608.8/pb ≈ARGUS+CLEO I (6 years) per month: 12.76/fb

Belle detector: 

Belle detector

Belle observation of a new narrow resonance X  J/: 

Belle observation of a new narrow resonance X  J/ Belle studied the decay of B+ into J/+-K+ final state (140fb-1) observed large B signal around M(J/)  M(’) as expected and significant excess at 3.870GeV/c2 Interpreted as a new hidden charm state Mbc M(J/) EB

X(3872) properties: 

X(3872) properties N = 35.7  6.8; significance 10.3 MX = (3872.0  0.6  0.5) MeV/c2;  < 2.3 MeV/c2 at 90% CL B (BXK)  B (XJ/+-) /B (B’K)  B (’J/+-) = 0.063  0.012  0.007 M+- tends to peak around limit It is unclear why… Similar tendency for ’J/+- is due to matrix element for 2S1S XJ/ is forbidden by isospin if X is charmonium

X(3872) properties: 

X(3872) properties Search for Xc1 Use ’c1 as a normalization mode; no signal for Xc1 is seen B (Xc1) /B (XJ/+-) < 0.9 at 90% CL

CDF confirmed Belle result: 

CDF confirmed Belle result N = 730  90; M = 3.871.3  0.7  0.4;  small; significance 11.6 M()>500MeV/c2 200pb-1

And DO too… : 

And DO too… The production mechanism(s) for X(3872) at Tevatron is still unclear: the most probable is prompt production. Tendency of a large M(+-) confirmed by CDF Tevatron large statistics warrants further studies: Angular analysis M(+-)? Production mechanisms

How to explain X(3872)?: 

How to explain X(3872)? The width is narrow + not seen in BDDK  XDD is forbidden by selection rules? Mass is exactly around DD* threshold MX - MDD* = (0.2  0.7) MeV/c2  XDD* forbidden or strongly suppressed Produced in B decays  high spin unlikely +- in s-wave: JPC=0++ +- in p-wave: JPC=1--

Charmonium assignment for X(3872)?: 

Charmonium assignment for X(3872)? c2(31S0): mass is too low (expected 4000 MeV/c2) & should not be narrow & J/+- decay violates isospin hc(21P1): angular distribution is wrong c1(23P1): (J/ ) is too small (expected 30(J/+- )) & J/+- decay violates isospin 2(13D2): (c1) is too small (expected > 2 (J/+- )) & M+- is wrong c2(11D2): not expected to decay into J/+- & J/+- decay violates isospin 3( 1F3): (c2) is too small (expected > 3 (J/+- ) ) & M+- is wrong Still no good (cc) candidate: if X(3872) turns out to be a charmonium, theory needs a lot of work

Can X(3872) be something else?: 

Can X(3872) be something else? A lot of papers devoted to exotic explanation of X(3872) due to Unusual for charmonium properties M close to D0D*0 threshold Weekly bound DD* resonance: hadronium  mesonic moleculedeuson Tornquist hep-ph/0308277; Braaten-Kusinoki hep-ph/0311147; Wong hep-ph/0311088 + many-many others Idea is quite old: first suggested by Voloshin-Okun JETP Lett. 23 p.333 (1976) to explain unusual properties of (4040); then reexploited for a variety of unusual mesons: f1(1420), (1440), fJ(1720), a0(980), f0(975) Charmonium hybrid state: Close-Page hep-ph/0309253 By summer 2004: Belle statistics 2 larger + BaBar hopefully joins efforts + Tevatron: Answer the question CX=+ or -? (J/00 )=(½ or 0)(J/+- ) Perform angular analysis (even now Belle succeeded to exclude hc’) Search for other modes; other production mechanisms (eeX; X)

Theory: 

Theory Kaydalov: apply Regge trajectories approach; no new free parameters (all are fixed from the old phenomenology): Found that (e+e- J/cc) is ~10 times larger than in pQCD. Mcc spectrum is similar to that measured by Belle ~7% of the spectrum below the DD threshold (double charmonium final state) Ioffe-Kharzeev: e+e- J/ cc can be a part of e+e- J/ gg: gg can fragment to light quarks coherently  if Mgg is large gg can fragment into SU(3) singlet (uu+dd+ss)/3 + cc. Expect (e+e  J/cc)/(e+e-  J/gg)~0.4+0.1(direct) Also explain large Mgg by scale anomaly in scalar state of gg More precise study for (e+e-→ J/cc) is required to test thes ideas.

Angular analysis: 

Angular analysis Belle: study J/ production and helicity angles for c, c0, c’ peaks Fit c, c0 and c’ yields in bins of cos(prod) and cos(prod); then correct for the efficiency Angular distributions as expected for double charmonium (c and c’ produced in p-wave, c0 – s-wave ) Another proposal: the peaks in the J/ recoil mass corresponds to glueballs: gg enriched process + some glueballs are predicted in this mass region Brodsky-Goldhaber-Lee predict d/dcos  ~ sin2 

Charmonium production in : 

Charmonium production in  Q2>>M2(cc)res Resolved gluon prod’n (Color singlet + Color octet) Vector-Meson dominance (Pomeron exchange + diffractive photon dissociation) Fraction of resolved gluon production (7422)% from the fit to pT Favor LARGE CS contribution (J/) = (45  9  17) pb