Spectroscopy issues at a Super B factory. Antimo Palano INFN and - PowerPoint PPT Presentation

✬ ✩ Spectroscopy issues at a Super B factory. Antimo Palano INFN and University of Bari Super-B factory Workshop, Hawaii, April 20, 2005. ✷ In the last few years charm and charmonium spectroscopy has received a new revival due to the discovery of new unexpected particles. ✷ New results on Spectroscopy from B-factories are coming from: • B decays; • Charm decays; • Inclusive e + e − interactions; • γγ collisions; • Initial State Radiation; ✷ Important issue for spectroscopy: Exclusive or Semi-exclusive reactions. ✫ ✪ 1

✬ ✩ Some Issues in Spectroscopy. ✷ Among the still unsolved questions heavy and light meson spectroscopy I will focus on: • Completing the charm and charmonium spectrum; • Solving the question of the existence of gluonium or hybrid states. ✫ ✪ 2

✬ ✩ The charm spectrum. ✷ The recent discoveries in the charm spectrum put back into question the validity of the potential models. ✷ Therefore it is important to establish the complete spectrum of charm. The cu/d spectrum. ¯ ✫ ✪ ✷ Where are the charm radial excitations? 3

✬ ✩ The charm spectrum. ✷ The ¯ cs spectrum after the discovery of the D sJ states. ✫ ✪ ✷ Are there still unexpected particles to be found? 4

✬ ✩ The new D sJ states. ✷ The new D sJ states have been interpreted as: • The missing c ¯ s states. For reasons still to understand potential models predict wrong masses. • 4-quark states or molecules. In this cases other states should be found. Some of them could be narrow. • The discovery of a new phenomenon such as Chiral Doubling? In this case again new states are expected to be found. M. A. Nowak et al., hep-ph/0307102 W.A. Bardeen et al., hep-ph/0305049 ✫ ✪ 5

✬ ✩ Charm spectrum: information from continuum. ✷ Narrow states can be extracted from continuum e + e − annihilations using hard p ∗ cuts. This is being done at current B-factories. ✷ The BaBar discovery of the new D sJ states: ✫ ✪ 6

✬ ✩ Charm spectrum: information from continuum. ✷ The process of isolating charm decays from continuum is quasi-exclusive: a large part of the non − c and combinatorial background is removed by applying a high p ∗ cut. ✷ However, spin-parity analysis is impossible in continuum production except for a few cases. ✷ Broad states cannot be isolated from continuum. ✷ Presence of reflections from other narrow states. ✫ ✪ 7

✬ ✩ Charm spectrum: information from B decays. ✷ Broad states can only be extracted from B decays. BELLE evidence for 0 (2308) → D + π − in B − → D + π − π − . D ∗ 140 Events/20 MeV/c 2 120 D * 2 D * 100 0 * ,B v * D v 80 60 40 20 0 2 2.5 3 3.5 M D π min (GeV/c 2 ) ✫ ✪ 8

✬ ✩ Charmonium spectrum. ✷ It is important to establish the complete spectrum of charmonium. 2S+1 L J 1 S 0 3 S 1 1 P 1 3 P 0 3 P 1 3 P 2 1 D 2 3 D 2 3 D 3 1 F 3 3 F 3 n.a. 5 0 +- 12 0 +- 4.5 1 -+ 11 2 +- 4 10 9 3.5 χ c 1 χ c 2 h c m/GeV χ c 0 m r 0 8 3 J/ Ψ η c 7 experiment DD ** 2.5 6 DD CP-PACS 2 Columbia 5 hybrids glueballs 4 1.5 1 +- 0 ++ 1 ++ 2 ++ 2 -+ 3 +- 3 ++ exotic J PC 0 -+ 1 -- 2 -- 3 -- ✷ Several states still missing. Are there hybrid charmonium states? ✫ ✪ 9

✬ ✩ Charmonium hybrids. ✷ S. Godfrey: the existence of gluonium excitations in the hadron spectrum is one of the most important unanswered questions in hadron physics. ✷ Hybrid mesons ψ g consists of ¯ ccg . ✷ The flux tube model predicts 8 states between 4 and 4.2 GeV. ✷ Lattice QCD calculations predict the J P C = 1 − + state between 4.04 and 4.4 GeV. The proximity of D ∗ D thresholds could make it narrow. ✷ Some hybrids can have exotic quantum numbers such as: ψ g ( J P C = 0 + − , 2 + − ) → J/ψ + ( π + π − ) , η, η ′ ψ g ( J P C = 1 − + ) → η c + ( π + π − ) , η, η ′ ✷ Some of these states could be produced in B decays. ✷ Hybrid mesons with J P C = 1 −− could be looked for in e + e − annihilations via ISR. ✫ ✪ 10

✬ ✩ Charmonium spectrum. ✷ New charmonium states can be extracted from B decays: ✷ The J/ψπ + π − mass spectrum from B decays in BELLE from B + → K + J/ψπ + π − : 400 Events/0.010 GeV/c 2 200 0 0.40 0.60 0.80 1.00 1.20 M( π + π - J/ ψ ) - M(J/ ψ ) (GeV/c 2 ) ✫ ✪ 11

✬ ✩ Charmonium spectrum. ✷ But also J P C = even x + can be obtained from γγ collisions. ✷ The Observation of η c and η c (2 S ) from BaBar from γγ . B A B AR ✷ γγ collisions are also an η c factory. ✫ ✪ 12

✬ ✩ Charmonium spectrum. ✷ The Observation of χ c 0 and χ c 2 from BELLE in γγ collisions. 300 π π Nevent / 20MeV + - + - 250 K K 200 χ c0 150 χ c2 100 50 0 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 W [GeV] ✷ γγ collisions are also a χ c 0 , 2 factory. ✫ ✪ 13

✬ ✩ Charmonium from ISR. ✷ The J P C = 1 −− charmonium states can be observed from ISR e + e − → γJ/ψ . ✷ The J/ψ → π + π − π 0 from BaBar. events/(2.5 MeV/c 2 ) 100 75 50 25 0 2.9 3 3.1 3.2 3.3 M 3 π (GeV/c 2 ) ✷ BaBar, for events having the ISR γ reconstructed : 10 events per fb − 1 . With 20 ab − 1 : 200 K events. Similar to the actual BES statistics. A super B-factory is also a charmonium factory. ✫ ✪ 14

✬ ✩ Status of gluonium searches. ✷ Lattice QCD predicts the scalar gluonium around 1.7 GeV: 12 +− 0 10 −− +− 3 2 4 −− *−+ 2 2 −− 1 ++ 3 *−+ 0 +− 3 8 −+ 2 3 +− 1 m G (GeV) *++ 0 −+ r 0 m G 0 6 ++ 2 2 4 ++ 0 1 2 0 0 ++ −+ +− −− PC ✫ ✪ 15

✬ ✩ Status of gluonium searches. ✷ Too many scalar mesons below 2. GeV. I = 1/2 I = 1 I = 0 k (800) σ a 0 (980) f 0 (980) ✷ Two nonets? 4-quark states? Gluonium? f 0 (1370) ✷ Where is the scalar glueball? K ∗ 0 (1430) a 0 (1490) f 0 (1500) ✷ Many proposals. f 0 (1700) Narrow: f 0 (1500), f 0 (1700). K ∗ 0 (1950) Wide: σ . ✷ Information on some of these states, such as the existence of k (800) and σ can be extracted from existing data from charm decays. ✷ Unlikely to produce gluonium in charm decays. ✫ ✪ 16

✬ ✩ Search for gluonium in B decays. ✷ The possibility of searching for gluonium in B decays has been suggested by the experimental measurement of a large decay rate for: B → η ′ X, B → η ′ K ✷ The diagram giving rise to these processes is: b → sg ✷ There are arguments in favour of a gluonic content of the η ′ , therefore gluonium states may be produced in B decays. ✫ ✪ 17

✬ ✩ ✷ The total rate b → sg has been calculated perturbatively: B ( b → sg ) = (2 − 5) × 10 − 3 ✷ One should look for: B → K ( ∗ ) ππ, KK, ηη, ηη ′ in searching for scalar or tensor states. ✷ One should look for: B → K ( ∗ ) ηππ, K ¯ Kπ in searching for pseudoscalar states. H. Fritzsch, Phys. Lett. B415 (1997) 83 P. Minkowski and W. Ochs hep-ph/0404194 ✫ ✪ 18

✬ ✩ Search for gluonium in B decays. ✷ Present data. Study of: B → K + scalar ( tensor ) ✷ BELLE: π + π − mass spectrum in B + → K + π + π − 180 30 160 Events/(0.05 GeV/c 2 ) (b) 25 140 20 120 15 10 100 5 80 0 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 60 40 20 0 0 1 2 3 4 5 ✷ Strong f 0 (980) signal. M( π + π - ) (GeV/c 2 ) ✷ Wide scalar structure around 1.3 GeV. f 0 (1300)? ✫ ✪ ✷ No f 0 (1500). 19

✬ ✩ Search for gluonium in B decays. ✷ BELLE: K + K − mass spectrum in B + → K + K + K − 120 60 Events/(0.05 GeV/c 2 ) 100 (d) 50 40 80 30 20 60 10 0 0.99 1.00 1.01 1.02 1.03 1.04 1.05 40 20 0 0.5 1 1.5 2 2.5 3 3.5 4 M(K + K - ) min (GeV/c 2 ) ✷ f 0 (1500) or f ′ 2 (1525)? ✷ Actually very limited statistics in the search for the pseudoscalar gluonium in: B → K ( ηππ ) , ( ηππ ) ✫ ✪ 20

✬ ✩ Gluonium in double charmonium sample? ✷ Observation by BELLE of an unexpected large rate for: e + e − → J/ψη c and e + e − → J/ψ (¯ cc ) N/20 MeV/c 2 75 100 50 25 75 0 3.5 3.6 3.7 3.8 3.9 4 4.1 4.2 50 25 0 2 2.5 3 3.5 4 4.5 Recoil Mass(J/ ψ ) GeV/c 2 ✫ ✪ 21

✬ ✩ Gluonium in double charmonium sample? This discovery has triggered triggered some authors to suggest that this rate may be partly due to the presence of a gluonium state: e + e − → ¯ ccgg H γ * G J S. Brodsky et al., hep-ph/0305269 ✫ ✪ 22

✬ ✩ Conclusions ✷ A Super B-factory is also a τ/charm factory but also a charmonium factory. ✷ Charm, charmonium, light and exotic meson spectroscopy can receive new inputs and possibly new unexpected states could be found. ✫ ✪ 23