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CHARMONIUM

CHARMONIUM. New era (~after 2001). This lecture is about the. where I hope to convince you that charmonium still has the potential to surprise us. B-factories. Superconducting Coil (1.5T). Silicon Vertex Tracker (SVT)[5 layers]. e + (3 GeV). e - (9 GeV). Aerogel Cherenkov cnt.

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CHARMONIUM

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  1. CHARMONIUM

  2. New era(~after 2001) This lecture is about the where I hope to convince you that charmonium still has the potential to surprise us

  3. B-factories Superconducting Coil (1.5T) Silicon Vertex Tracker (SVT)[5 layers] e+ (3 GeV) e- (9 GeV) Aerogel Cherenkov cnt. n=1.015~1.030 Drift Chamber [40 stereo lyrs](DCH) SC solenoid 1.5T 3.5GeV e+ CsI(Tl) 16X0 TOF counter 8GeV e- Tracking + dE/dx small cell + He/C2H5 CsI(Tl) Calorimeter (EMC) [6580 crystals]. pp collider CDF D0 E ~ 1.8 TeV ¯ Cherenkov Detector (DIRC) [144 quartz bars, 11000 PMTs] m / KL detection 14/15 lyr. RPC+Fe Si vtx. det. 3 lyr. DSSD Instrumented Flux Return (IFR) [Iron interleaved with RPCs]. e+e- → Y(4S) BaBar Belle E=10.6GeV L~1033/cm2/s e+e– → сharmonium CLEO-c BES-II E=3.0-4.8GeV L~1033/cm2/s

  4. Controversal tests of COM model Leptoproduction at HERA: COM predicts too high x-section Photoproduction at HERA: COM is ok gg-production at LEP: COM expectation are in a nice agreement with the data

  5. Charmonium production in e+e– at E~10GeV • Color-Singlet e+e- J/ cc was estimated to be very small by Kiselev et al.(1994) •  ~ 0.05 pb  should be unobservable even at high luminosity B-factories • Color-octete+e-  (cc)8 g J/ g (with Oncc fixed to Tevatron and others data) should not be large as well (but can be significant around the end-point of J/ momentum) Braaten-Chen (1996) • Color-Singlet e+e- J/ gg is the best candidate! Predicted CS ~1 -2 pb Cho-Leibovich (1996) was first observed experimentally (although it is not so much surprising, nobody thought about this possibility). CLEO/Argus, 1992: cross section e+e- J/~ 2 pb.

  6. Surprisingly large double charmonium production • Look at the recoil mass against reconstructed J/ using two body kinematics (with a known initial energy) • Mrecoil = (Ecms- E J/ )2 - P J/2 ) • See all the (narrow) states produced together with J/y. • The data shows unexpected charmonia: hc, cc0, hc(2S) • Note: all recoil states are 0±+. C=+1 is expected: C(g)=–1, C(J/y)=–1 Belle(2002) BaBar (2005) experiment ~10*theory

  7. Belle(2002) Surprisingly large J/y production with charm mesons • Double charmonium is not a whole story, in addition, also observed associated production • e+e–J/ D(*+) X • e+e–J/ D0 X • demonstrating large e+e- J/ cc unlike theory expectation (e+e-→ J/cc)/(e+e-→ J/X) =0.590.140.12 (e+e–→ J/cc)~ 1pb ~10-20 times greater than theory expects This results do not kill COM, but remove the basis for it: If CSM can not calculate correctly c→J/y fragmentation (as demonstrated by these data), why do we need COM (suggested to resolve discrepancy CSM-data).

  8. Back to charmonium spectroscopy D* H0 ¯ D Hint ? H2 • 1974-1980, ten charmonium states observed (1.5 per year) • 1980-2002, no new state found • Potential models successfully describe the charmonium spectrum, annihilation decays and radiative transitions • 2002-2007, ~ twelve new charmonium (charmonium-like) states found. Do they fit the potential model? One more important ingredient: to take into account charmed meson-antimeson pair coupling to charmonium. Important above DD threshold. • Cornell coupled channel model • Model of quark pair production in vacuum

  9. How to identify it? If you find a new charmonium state “X”, than • Quantum numbers can be fixed at production: • In e+e– annihilation (including annihilation after initial state radiation),only the states with quantum number of photon can be produced (JPC=1- -) • Inggfusion,only the states with C=+1, J=0,2 are produced • In double charmonium productione+e–→g*→ Xcc1Xcc2, only if two charmonium can form 1- - (if you know quantum number of one of the states you can say something about accompaning one). • In B-decays and in hadronic interaction, generally no constrain. P non conservation in weak decays/not understanding of production mechanism. • ... Or in “X” decay • Selection rules: angular momentum, P, C conservation in strong and electromagnetic decays. • The most powerfull tool is to study angular distributions, depending on JP . It is even more powerful when “X” is found in B decay.

  10. Observation of hc CLEO 2005 M(hc) = (3524.4 ± 0.6 ± 0.4) MeV y(2S) → p0hc→ p0ghc hc Potential model expectations: M(hc) = centre of gravity of cc states = 1/9 * [(2*2+1) * M(cc2) + (2*1+1) * M(cc1) + (2*0+1) * M(cc0) ] = 3525.3 ± 0.3 MeV This prediction is independent on the potential. This measurement unfortunately does not check the models.

  11. Belle, 2002 Observation of c(2S) • observed • in B decays (c(2S)KSK) • in e+e- annihilation (inclusive) • confirmed by CLEO & BaBar in  • B(KSK)K M=265410 MeV/c2 <55MeV the properties are in reasonable agreement with the expectations (mass, total width, -width) c(2S) e+e- J/c(2S) M=263012 MeV/c2 Chramonium table below DD threshold is complete!

  12. Belle, 2003 New unexpected particle X(3872) – the first in “X” series introduce new (ugly) particle naming scheme: X, Y, Z ... The B-meson signal depending on M(J/ypp) Everything is surprising: • observed in the decay B+(J/)K+ • MX=(3872.00.60.5)MeV/c2 • MX - MDD* = (0.2  0.7) MeV/c2 • narrow:<2.3MeV at 90% CL • decay dynamics:M+- tends to peak around limit (J/ 0 is isospin violating decay) M(p+p–)

  13. At pp collision only ~10% produced from B-decays, others are directly produced (new headache for “production” theory) ¯ Belle Confirmed by CDF,D0,BaBar X(3872) is well established, can not be attributed to experimental mistake

  14. more information – more understanding? - X decays to J/y g, but very rarely (Belle 2004, BaBar 2006). This observation fix CX=+1, and confirm that in the X→J/ψppdecay (pp)=r. This only add confusion: if X-charmonium, the radiative decays should be stronger than X→J/ψ r transition. - X decays to J/y w with Br ~ Br (X→J/ψpp). This confirms isospin violation. - Fit to M(pp) favours PX=+1. - Angular analysis: JPC=1++ corresponds to c1(23P1) if X-charmonium: - c1’ J/ should be much stronger than c1’ J/ (measured ratio ~0.15, expected ~ 30) - ~100MeV/c2 lighter than expected. Belle, 2004 CDF, 2006 Favours JPC = 1++ • JPC=2–+c2(11D2):is expected to decay into hadrons (via gg) rather than into isospin violating mode.

  15. Options for X(3872) 1++ is predicted Vote: Absolute winner X ≡ D0D*0 molecule

  16. Tetraquark hypothesis c c B0→XKS d c u c d u Xd = Xu = B±→XK± expects several X states around 3872 with a typical splitting ~ 4-5MeV Predictions: #1 there should be charged state (difficult to check experimentally) #2 the X-states produced in B0 and B+ are different and should have different masses (this is finally checked in 2007(Belle)) • MX=M(X from B±) ─ M(X from B0)=(0.22±0.90±0.27)MeV/c2 • No mass splitting expected by tetraquark model • Br(B0→X(3872)K0)/Br(B±→X(3872)K±) =0.94±0.24±0.10 • equalBR for neutral and charged B, is this a big problem for molecular model? Some molecular models predicts this ratio 1/10.

  17. Decay to D0D0p0 • Looking for B XK , XD0D0p0 (D0D*0 ) • Belle 2006, BaBar 2007 Good agreement betweenBelle/BaBar, ...but 4 fromM(X→J/ψpp) • Is this a new state, different from X(3872)? • If X(3872) is DD* molecular state with the pole just below the DD* threshold, this observation is not surprising. Such model expects: • X→J/ψpp with unresolvable width exactly at the DD* threshold • Flatte-likeXD0D0p0behaviour with a typical “width” of 3MeV

  18. Belle, 2004 BaBar, 2007 One more misterious state Y(3940) BYK, YJ/y w +3.8 −3.4 • M= 3914.6  1.9 MeV • tot = 33  5 MeV +12 −8 BYK • M= 3943  11  13 MeV • tot = 87  22  26 MeV B0YKS B0/B M(J/y w) (GeV) The state is well above both DD and DD* thresholds. At least one of these final state is allowed for charmonim. Why it is not seen in any of these final state? M(J/y w) (GeV)

  19. Belle,2005 c2’ in  production • Observed as a peak at MDD~3.930 GeV/c2 in selected  events • pt distribution consistent with  production Helicity distribution favors spin = 2 while J=0 disfavored M=393142MeV/c2 =2083MeV (2J+1)× B(ZDD)=(1.130.30)keV The observed state is c2’: However, the mass is ~80-100 MeV lighter than expected by potential models

  20. Belle, 2005 Belle, 2007 New states ine+e− J/ D(*)D(*) D* M = 3942 ±6 MeV tot =37 ±12 MeV +7 -6 D*π D +26 - 15 D* D +25 −20 • M= 4156 15 MeV • tot = 139 21 MeV +111 −61 X(3940) → DD* X(4160) → D*D* Two new states observed, both decay at open charm final states like “normal” charmonium. Possible assignments are hc(3S) and hc(4S). But in both cases the masses predicted by the potential models are ~100-150 MeV lower. Theory probably needs more elaborated model to take into account couple channel effects.

  21. BaBar 2005, CLEO,Belle,2006 g e– e– (2S) s=(Ecm-Eg)2-pg2 e+ 1–– final state Another enigmatic particle(s) = Y(4260)→J/ypp New state? Consistent with BaBar

  22. BaBar 2005, CLEO,Belle,2006 g e– e– s=(Ecm-Eg)2-pg2 e+ 1–– final state More states? = Y(4350)→y(2S)pp Y(4360) consistent withBaBar Y(4660) NEW

  23. e+e–→J/+– & e+e–→ (2S)+– • Peak positions in M(J/) & M((2S))significanctly different. There is no place in the 1–– charmonium spectrum even for one state...

  24. Inclusive cross section arond 4 GeV PDG 2006 Y(4260) • In spite of ψ(3770), ψ(4040), ψ(4160), ψ(4415)are know for more 25 years, their parameters M,, eeare quite uncertain: • To fix the parameters we need to know their decays channels (to take into account their interference: if two states decays into the same final state they should interdere, if into different final states their contribution are uncoherent) • How to take into account non-resonance contribution • Need to take into account DD thresholds (~ 50 ...)

  25. BES-II 2007 New fit to the inclusive spectrum arXiv:0705.4500 Resonance parameters Rres=RBW+Rint Resonance shapes Interference term The interference is taken into account for the first time (model dependent) Significant difference with fit without interference We need exclusive cross sections e+e−→D(*)D(*) for model independent fit

  26. Belle 2006, CLEO 2007 Exclusive e+e−→D(*)D* cross-sections g e– e– s=(Ecm-Eg)2-pg2 e+ 1–– final state D(*)D* = Y(4260) signal DD* : hint, but not significant D*D* : clear dip D*+D*- D*D* y(4160) y(4415) Charged D(*)D* ½ from CLEOc y(4040) y(4160) Y(4260) y(4040) D+D*- DD* Y(4260)

  27. Observation of the decay (4415)DD (4040) g (4160) e– e– (3770) (4415) s=(Ecm-Eg)2-pg2 e+ 1–– final state Belle 2007 DDp = DD DD*2(2460) ~10σ DD non DD*2(2460) M(D0+) vs M(D-+) from(4415) region Positive interference Non D*2(2460) contribution is not seen

  28. Contributions to the inclusive cross-section D*D* DD + + 2× DD* DDp = 2× uds-continuum Anything else? These 4 final states almost saturate inclusive cross section, still many missing f.s. e.g. Ds(*)Ds(*)

  29. Belle,2007 Resonance? in p+y(2S) Dalitz plot for signal events ??? M2((2S)), (GeV2 ) K*(1430)→K+- M2(K), (GeV2 ) K*(890)→K+- B → Kp+ y(2S), (2S)→ℓ+ℓ–; p+p-J/y K*(890) & K*(1430)excluded M = (4433±4±2) MeV G = (45+18-13+30-13) MeV 7.3 M(p+y(2S)) The first charmonium-like state, for which charmonium assignment is impossible. Is this a state or threshold effect (cusp)? Tetraquark or meson molecularstate? or charmonium-light meson molecule-like state?

  30. Trying to put all new state in the table Placed here by JPC Y(4660) (4415) M(MeV) Y(4350) Z+(4440) X(4160) (4160) Y(4260) cc2’ Y(3940) (4040) X(3940) DD X(3872) (3770) ’ h’c cc2 cc1 hc cc0 J/ hc JPC

  31. New charmonium /charmonium-like states: • 2 new states below open charm threshold: hc and hc(2S) are well identified and well fit the potential model prediction • 3 new states (cc2(2P), X(3940), X(4160)) behave like a normal charmonium, but all three are significantly lighter than expected by potential model. This can be corrected by modifying the charmonium-charm mesons interaction. • 1 state X(3872) is very probably to be a D0D*0 molecular state (not a big exotics) with probably a mixture of cc1(1P), cc1(2P). At least there is no better explanation... • 1 state Y(3940) is probably a normal charmonium - experimental information is still poor. The only • 4 states in 1–– spectrum are the most problematic. The best quantative prediction is that these states are hybrids (ccg) (expected by LQCD calculation in this mass region). Note of the Voloshin’s explanation (lecture on the first day of the school). • Charged charmonium-like state Z+(4430) may be a tetraquark. Note of the Voloshin’s explanation

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