Hadronic (ns) decays. VI International Workshop on Heavy Quarkonia, Elisabetta Prencipe On behalf of the BaBar collaboration

Transcription

1 VI International Workshop on Heavy Quarkonia, 2008 Hadronic (ns) decays at BABAR Nara, 2 th 5 th December 2008 Elisabetta Prencipe On behalf of the BaBar collaboration

2 Introduction Studying Quarkonia studying strong interactions Measure masses, electromagnetic/hadron transitions, rates, splitting Comparison charmonium/bottomonium spectrum New forms of aggregation, mediated from strong interactions u c u c Recent observations of (unexpected) new states. Several states missing in the spectrum, and others do not fit theoretical predictions. Many subsequent interpretations of these new states and methods were suggested to analyse their structure (HQT, chiral symmetries, 4-quark models, bag model, Lattice...). u c _ c _ u c c _ g tetraquark DD* molecule hybrid 2

3 BABAR is a B-factory Wide amount of collected data allows to do spectroscopy studies. (e + e Hadrons)(nb) = 54 kev VIS.=20nb = 32 kev VIS.=7nb = 20 kev VIS.=4nb Y(nS) resonances = 20 MeV (1S) (2S) (3S) (4S) Mass(GeV/c 2 ) The spectrum of Heavy Quarkonia is an ideal place to provide precision tests of QCD. Heavy Spectroscopy studies can be performed in e + e interaction at (4S): charm and charmonium (production in continuum, B decays); bottomonium (hadronic Y(nS) transitions, scan at (4S), invisible decays); (ns) are also produced at (4S) via ISR: e + e (ns) 3

4 Why do we study hadronic transitions? The main goal to run at (2S) and (3S) in BABAR has been to search for bottomonium states and light Higgs. Bottomonium spectrum offers the possibility to look _ at many hadronic transitions, because of the non-relativistic nature of bb-system and the richness of the spectrum of the states below open-bottom threshold. Hadronic transitions provide an excellent testing ground for non-perturbative QCD: detecting h b studying b (ns) (ms) transitions Hadronic transitions represent an important tool to fully understand the spectrum. Only 6 transitions were known. Today we can say much more! 4

5 transitions in bottomonium Studying transitions is important: transitions among vector states (4S) and (5S) to lowest bottomonium states; (4260) to J/ and the same for (3770); transitions among bottomonium states below open-bottom threshold (3S), (2S) (1S) to study exclusive (1S) decays, including invisible decay modes. 5

6 Mass (GeV/c 2 ) BOTTOMONIUM SPECTRUM b (3S) (11020) (10860) (4S) (3S) BB h b (2P) b (2P) _ BB threshold ( 3 2D) ( 3 1D) _ bb-bound states: Spectrum described with potential model: Coulomb + linear term All singlet states were missing, including the ground state b (1S) b (2S) b (1S) (2S) (1S) h b (1P) + transition S P D b (1P) see Kim's talk 2 h b and 3 D wave states are narrow but not observed. Many hadronic transitions available to search for missing states. J PC = 0 + L = (0,1,2) ++ (1,2,3) Sensitive to S 6

7 Hadronic transitions (ns) (ms) Hadronic transitions between heavy quarkonium states can be described with the QCD multiple expansion model (QCDME) PRD 24, 2874 (1981) Y.P. Kuang, T.M. Yan in analogy with electromagnetism, it is possible to expand _ in terms of (ak) gluon radiation if the radius a of the bound qq state is much smaller than the wavelenght 1/k vicinity to threshold opening can modify QCDME predictions m 3 S 1 n 3 S 1 (E1E1) m 3 S 1 n 3 S 1 (E1M2 or M1M1) 7

8 In the charmonium system data agree with predictions BR((2S) (2S)J/ J/)/BR( )/BR((2S) J/ is well explained. M( ) in the transition (2S) (2S) J/is well described. In the bottomonium system more transitions are available: more comparisons! _ bb-system offers unique opportunities: 5 known m 3 S 1 n 3 S 1 and also 4 kinematically allowed transitions involving a meson. M( ) distribution in (3S) (3S) (2S) (2S), (2S) (2S) (1S) agree with QCDME. M( ) in (3S) (3S) (1S) is not in agreement (known!) with QCDME model; this is confirmed also above open-bottom threshold. Now it is possible to study better the discrepancy from QCDME large transitions measured with high precision. 8

9 Experimental results of hadronic transitions are now presented. (4S) (1S) (4S) (2S) (4S) (1S) (3S) (1S) (3S) (2S) (3S) (1S) (2S) (1S) (2S) (1S) 9

10 (4S) Transitions PRL96, Non BB decays Transitions: (4S) (2S) (2S) (4S) (1S) (1S) First observation on 230M (4S) Reconstructed: (4S)(nS), (ns)l + l M(l + l ) compatible with (ns) = M( l + l ) M(l + l ) compatible with M(4S) M(nS) BR calculated for each mode. old results 10

11 11 (ns) (ms) (ms) : new results Update on 382 M (4S) arxiv: (2S) (1S) (1S) (3S) (1S) (1S) (3S) (2S) (2S) (4S) (1S) (1S) (4S) (2S) (2S)

12 How the BR was calculated in Y(nS) analyses Efficiency-corrected yields for each mode. DATA/MC correction applied. Taking into account (4S) numbers or the equivalent (equivalent ISR luminosity). narrow resonance produced in ISR QCD radiator function, calculated to the second order The angular distribution of di-lepton decays incorporates the (4S) polarization, while di-pion transitions are generated according to phacespace model. Dalitz model-independent method in (4S) (ms) to evaluate acceptance. The uncertainty was calculated by the change in the signal yields using different m and cos h binnings. 12

13 13 invariant mass distribution PRL96, (4S) (4S) (1S) (4S) (4S) (2S) Efficiency estimated by MC sample. Large systematics due to unknown -mass distribution in (4S) (ms) (phase space QCDME model). M distribution determined by fitting M in equal intervals of M and dividing the number of signal events in each interval by the corresponding selection efficiency. Acceptance calculated assuming phase-space function in (4S) (ms). Looking at M : GOOD agreement with QCDME in 4S1S; low mass structure in 4S2S?

14 (ns) transitions arxiv: Transitions: (4S) (1S) (3S) (1S) (2S) (1S) reconstructed: (ms)(1s), (1S)l + l (2S) and (3S) selected from ISR production from (4S) 0 = M( 0 l + l ) M(l + l ) M( 0 ) = M(mS) M(nS) - M() B 4S1S = (1.96± ) 10-4 (4S) (1S) Unexpected result: 4S1S 4S1S = 2.41±0.40±0.12 E1M2/ E1E1 This is NOT the mass! 14

15 many results from these analyses Summary of arxiv: non BB decays of (ms) rates and B.R. error improved: it is smaller than on the world average unexpected result 15

16 16 Comparison (5S) (ns) rates are large as well...(belle results!) transition BABAR (BR) CLEO (BR) (3S) (1S) (2S) (1S) (3S) (1S) (2S) (1S) (4.17±0.06±0.19 ) 10-2 (4.46±0.01±0.13 ) 10-2 (17.22±0.17±0.75 ) 10-2 (18.02±0.02±0.61 ) 10-2 < < < (2.1 ±0.5 ) Ref.(BABAR): arxiv Ref.(CLEO): arxiv ; arxiv new measurements, still not included in the world average The agreement is very GOOD!

17 Conclusions 30 years after the bottomonium was discovered the interest in this field of physics is still high! BABAR has performed BR measurements of high precision on (4S) (ns) (ns): the error is smaller than the world average. Unexpected result has been found analysing the transition: (4S) (1S) Many ongoing analyses with the full dataset (2S) (2S), (3S) (3S), (4S) (4S). These results, with the new CLEO measurements of the matrix elements in (3S) (1S, 2S) and (2S) (1S) transitions, can provide tools to understand hadronic transitions better. BABAR will continue to give its contribution! 17 どうもありがとうございます

18 Backup slides

19 BaBar: Who? Where? What? Asymmetric e + e PEPII Peak luminosity: cm 2 s 1 _ >500M BB produced (2008) 11 countries and 500 physicists! s = GeV e Y(4s) e +

20 (3S) (3S) (2S) (2S) Additional studies reported to explain how the signal region was selected

21 (4S) (1S) Additional studies reported to explain how the signal region was selected