May 14, 2003 Curtis A. Meyer 1 Carnegie Mellon University May 14, 2003 An Experimental Overview of Gluonic Mesons

May 14, 2003 Curtis A. Meyer 2 Talk Outline What are gluonic excitations ? Hybrids and Glueballs Overview of evidence for exotic quantum number states. Non-exotic quantum number states. Overview of Glueballs.

May 14, 2003 Curtis A. Meyer 3 quark-antiquark pairs u d s u d s J=L+S P=(-1) L+1 C=(-1) L+S G=C (-1) I (2S+1) L J 1 S 0 = S 1 = 1 -- ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= radial orbital Non-quark-antiquark … Normal Mesons

May 14, 2003 Curtis A. Meyer qq Mesons L = Each box corresponds to 4 nonets (2 for L=0) Radial excitations (L = qq angular momentum) exotic nonets 0 – – – 1 – + 1 – – 2 – – – + 2 – Glueballs Hybrids Lattice GeV Spectrum GeV

May 14, 2003 Curtis A. Meyer 5 Lattice QCD From G. Bali Flux Tubes Realized Confinement arises from flux tubes and their excitation leads to a new spectrum of mesons Color Field: Because of self interaction, confining flux tubes form between static color charges

May 14, 2003 Curtis A. Meyer 6 m=0 CP=(-1) S+1 m=1 CP=(-1) S Flux-tube Model ground-state flux-tube m=0 excited flux-tube m=1 built on quark-model mesons CP={(-1) L+S }{(-1) L+1 } ={(-1) S+1 } S=0,L=0,m=1 J=1 CP=+ J PC =1 ++,1 -- (not exotic) S=1,L=0,m=1 J=1 CP=- J PC =0 -+, , ,2 +- exotic normal mesons Hybrid Mesons 1 -+ or 1 +-

May 14, 2003 Curtis A. Meyer 7 Hybrid Predictions Flux-tube model: 8 degenerate nonets 1 ++, ,0 +-,1 -+,1 +-,2 -+,2 +- ~1.9 GeV/c 2 Lattice calculations nonet is the lightest UKQCD (97) 1.87  0.20 MILC (97) 1.97  0.30 MILC (99) 2.11  0.10 Lacock(99) 1.90  0.20 Mei(02) 2.01  0.10 ~2.0 GeV/c 2 In the charmonium sector:   0.11 Splitting = Splitting  0.20 S=0 S=1  0.50

May 14, 2003 Curtis A. Meyer 8 Decays of Hybrids The angular momentum in the flux tube stays in one of the daughter mesons (L=1) and (L=0) meson.  1   b 1,  f 1, ,  a 1 1:.25:.25:.20  1  (1300) , a 1   b 2  a 1 , h 1 ,  a 2  h 2  b 1 ,  b 0   (1300) , h 1  h 0  b 1 , h 1  L flux Exotic Quantum Number Hybrids Mass and model dependent predictions

May 14, 2003 Curtis A. Meyer 9 What role do gluons play in the meson spectrum? Lattice calculations predict a spectrum of glueballs. The lightest 3 have J PC Quantum numbers of 0 ++, 2 ++ and The lightest is about 1.6 GeV/c 2 Morningstar et al. f 0 (980) f 0 (1500) f 0 (1370) f 0 (1710) a 0 (980) a 0 (1450) K* 0 (1430) Glueball Mass Spectrum

May 14, 2003 Curtis A. Meyer 10 Glue-rich channels G M M Proton-Antiproton Annihilation Central Production (double-pomeron exchange) Radiative J/  Decays 0 -+  (1440) 0 ++ f 0 (1710) Large signals Glueballs should decay in a flavor-blind fashion f 0 (1370),f 0 (1500) 0 ++ f 0 (1370),f 0 (1500), f 0 (1710)

May 14, 2003 Curtis A. Meyer 11   p    p (18 GeV) The a 2 (1320) is the dominant signal. There is a small (few %) exotic wave. Interference effects show a resonant structure in  . (Assumption of flat background phase as shown as 3.)    Mass = MeV/c 2 Width= MeV/c 2 a2a2  E852 Results Exotic Quantum Numbers 1 -+ in 

May 14, 2003 Curtis A. Meyer 12   (1400) Mass = MeV/c 2 Width= MeV/c 2 Same strength as the a 2. Produced from states with one unit of angular momentum. Without  1  2 /ndf = 3, with = 1.29     Crystal Barrel Exotic Quantum Numbers 1 -+ in 

May 14, 2003 Curtis A. Meyer 13 Significance of signal.

May 14, 2003 Curtis A. Meyer 14 At 18 GeV/c suggeststo partial wave analysis E852 Results Exotic Quantum Numbers 1 -+ in 

May 14, 2003 Curtis A. Meyer 15 Leakage From Non-exotic Wave due to imperfectly understood acceptance Exotic Signal Correlation of Phase & Intensity  1 (1600) 3  m=  = Exotic Quantum Numbers 1 -+ in  E852 Results

May 14, 2003 Curtis A. Meyer 16 E852 Results  - p   ’  - p at 18 GeV/c The  1 (1600) is the Dominant signal in  ’ . Mass =  GeV Width =  GeV  1 (1600)   ’  Other reports here:  1 (1600)  b 1   1 (1600)  f 1  , b 1 , f 1 ,  ’  Exotic Quantum Numbers 1 -+ in  ’ 

May 14, 2003 Curtis A. Meyer 17 VES Results  1 (1600) observed in  A reactions m=1.6  0.02 GeV/c 2  =0.29  0.03 GeV/c 2 b 1  :  ’  :  = 1 : 1.0  0.3 : 1.6  0.4  - A  (A) (at 37 GeV/c) b 1  (1 -+ ) Phase wrt 2 + Exotic Quantum Numbers 1 -+ in , b 1  and  ’ 

May 14, 2003 Curtis A. Meyer 18 Exotic Signals  1 (1400) Width ~ 0.3 GeV, Decays: only  weak signal in  p production (scattering??) strong signal in antiproton-deuterium.  1 (1600) Width ~ 0.16 to 0.3 GeV, Decays ,  ’ ,(b 1  ) Only seen in  p production, (E852 + VES)  1 I G (J PC )=1 - (1 -+ )  ’ 1 I G (J PC )=0 + (1 -+ )  1 I G (J PC )=0 + (1 -+ ) K 1 I G (J PC )= ½ (1 - ) In a nonet, there should only be one  1 state. Both of these are lighter than expectations, and The  [  ’]  decay modes are not what are expected.

May 14, 2003 Curtis A. Meyer 19 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L=

May 14, 2003 Curtis A. Meyer 20 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= a 1,f 1,f’ 1,K 1 1 st radial excitation

May 14, 2003 Curtis A. Meyer 21 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= ,K* 1 st /2 nd radial excitation L=2 orbital excitation

May 14, 2003 Curtis A. Meyer 22 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L=  ’,K 2 nd radial excitation

May 14, 2003 Curtis A. Meyer 23 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= b 1,h 1,h’ 1,K 1 1 st radial excitation

May 14, 2003 Curtis A. Meyer 24 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= L=2 orbital excitation plus radial  2,  2,  ’ 2,K 2

May 14, 2003 Curtis A. Meyer 25 Hybrid Mesons with normal QN’s Assume that  1 (1600) sets the mass scale S=0 : 1 ++,1 -- S=1 : 0 -+,1 +-,2 -+ Non-exotic hybrid QN’s ,K*  ’,K L= a 2,f 2,f’ 2,K 2 a 1,f 1,f’ 1,K 1 a 0,f 0,f’ 0,K 0 b 1,h 1,h’ 1,K 1 L=  3,  3,  3,K 3  2,  2,  2,K 2  1,  1,  1,K 1  2,  2,  ’ 2,K 2 L= b 1,h 1,h’ 1,K 1 a 1,f 1,f’ 1,K 1 ,K*  ’,K  2,  2,  ’ 2,K 2

May 14, 2003 Curtis A. Meyer 26 The 1 ++ Mesons 1 ++ : 1 st Radial Excitation of a 1 (1260)/f 1 (1285) a 1 (1640) m=1.64  0.05 GeV/c 2  =0.30  0.1 GeV/c 2 Decays to 3  via f 2  and (  ) S  Consistent with a normal meson

May 14, 2003 Curtis A. Meyer 27 The 1 -- Mesons 1 -- : 1 st Radial Excitation of  / . 2 nd Radial Excitation of  / . L=2 D-wave (  1,  2,  3 )  (1450)  (1700)  (1900)  (1420)  (1650)   (1690)   (1670)   (1850)  (1680)  (2150) L=2 Scale Decay modes are significant here, but data is hard to interpret.

May 14, 2003 Curtis A. Meyer 28 The 0 -+ Mesons  (1800)  (1760) m=1.801  GeV/c 2  =0.210  GeV/c 2 m=2.230  GeV/c 2  =0.150  large GeV/c 2 Produced in J/ , decays to 4  Decays: f 0 (980) , f 0 (1370) , ,  a 0 (980)  f 0 (1500)   (2225) Produced in J/ , decays to  Speculation that this may be a hybrid Glueball quantum numbers

May 14, 2003 Curtis A. Meyer 29 The 1 +- Mesons 1 +- : 1 st Radial Excitation of the b 1 (1235)/h 1 (1170) h 1 (1595) m=1.594  0.05 GeV/c 2  =0.384  0.15 GeV/c 2 Produced in  p interactions Decays to  Consistent with a normal meson ?

May 14, 2003 Curtis A. Meyer 30 The 2 -+ Mesons  2 (1670)  2 (1870)  2 (1645) m=1.842  GeV/c 2  =0.225  GeV/c 2 m=1.617  GeV/c 2  =0.181  GeV/c 2 m=1.67  0.02 GeV/c 2  =0.259  GeV/c 2 Decays: a 2 , f 2 , a o  a 2  is largest) Decays: a 2 , KK , a o  a 2  is largest) Decays: f 2 , , (  ) S  f o (1370)  KK   f 2  is 56%)  2 (2100) Decays: f 2 , , (  ) S  m=2.090  GeV/c 2  =0.625  GeV/c 2 Hybrid Candidate?

May 14, 2003 Curtis A. Meyer 31 Exotics and QCD In order to establish the existence of gluonic excitations, We need to establish the nonet nature of the 1 -+ state. We need to establish at other exotic QN nonets – the 0 +- and In the scalar glueball sector, the decay patterns have provided the most sensitive information. I expect the same will be true in the hybrid sector as well. DECAY PATTERS ARE CRUCIAL

May 14, 2003 Curtis A. Meyer 32 Crystal Barrel f 0 (1500) f 2 (1270) f 0 (980) f 2 (1565)+  700,000  0  0  0 Events f 0 (1500) 250,000  0 Events Discovery of the f 0 (1500) f 0 (1500)   ’, KK, 4  f 0 (1370)   s Establishes the scalar nonet Solidified the f 0 (1370) Discovery of the a 0 (1450) Results on Scalars

May 14, 2003 Curtis A. Meyer 33 The f 0 (1500) Is it possible to describe the f 0 (1500) as a member of a meson nonet? Use SU(3) and OZI suppression to compute relative decays to pairs of pseudoscalar mesons Get an angle of about 143 o 90% light-quark 10% strange-quark Both the f 0 (1370) and f 0 (1500) are

May 14, 2003 Curtis A. Meyer 34 WA102 Results Central Production Experiment Recent comprehensive data set and a coupled channel analysis. CERN experiment colliding p on a hydrogen target.

May 14, 2003 Curtis A. Meyer 35 Meson Glueball Mixing Physical Masses f 0 (1370),f 0 (1500),f 0 (1710) Bare Masses: m 1,m 2,m G (G) (S) (N) f 0 (1370)    0.07 f 0 (1500)   0.04 –0.70  0.07 f 0 (1710) 0.39    0.02 m 1 =1377  20 m 2 =1674  10 m G =1443  24 octet piece Lattice of about 1600

May 14, 2003 Curtis A. Meyer 36 Glueball Expectations Antiproton-proton: Couples to Observe: f 0 (1370),f 0 (1500) Central Production: Couples to G and in phase. Observe: f 0 (1370),f 0 (1500), weaker f 0 (1710). Radiative J/  : Couples to G, |1>, suppressed |8> Observe strong f 0 (1710) from constructive |1>+G Observe f 0 (1500) from G Observe weak f 0 (1370) from destructive |1>+G Two photon: Couples to the quark content of states, not to the glueball. Not clear to me that has been seen.

May 14, 2003 Curtis A. Meyer 37 Higher mass glueballs? Part of the CLEO-c program will be to search for glueballs in radiative J/  decays. Lattice predicts that the 2 ++ and the 0 -+ are the next two, with masses just above 2GeV/c 2. Radial Excitations of the 2 ++ ground state L= States + Radial excitations f2(1950), f2(2010), f2(2300), f2(2340)… 2’nd Radial Excitations of the  and  ’, perhaps a bit cleaner environment! (I would Not count on it though….) I expect this to be very challenging.

May 14, 2003 Curtis A. Meyer 38 The Future CLEO-c will reopen the J/  studies with 100 times Existing statistics. One goal is to find and study the Pseudoscalar (0 -+ ) and tensor glueball (2 ++ ) The GlueX experiment will be able to do for hybrids what Crystal Barrel and WA102 (together) did for glueballs. What are the properties of static glue in hadrons and how is this connected to confinement. The antiproton facility at GSI (HESR) will look for hybrids in the charmonium system. (Just approved by the German government.) The CLAS experiment at Jefferson Lab is opening a small window to meson spectroscopy in photoproduction.

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May 14, 2003 Curtis A. Meyer 40

May 14, 2003 Curtis A. Meyer 41 linear potential ground-state flux-tube m=0 excited flux-tube m=1 Gluonic Excitations provide an experimental measurement of the excited QCD potential. Observations of exotic quantum number nonets are the best experimental signal of gluonic excitations. QCD Potential

May 14, 2003 Curtis A. Meyer 42 Strong QCD See and systems. white Color singlet objects observed in nature: Allowed systems:,, Focus on “light-quark mesons” Quarks in 3 colors 8 Gluons carry color & anticolor Glueballs Hybrids 4-quark

May 14, 2003 Curtis A. Meyer 43 Nonet Mixing The I=0 members of a nonet can mix: SU(3) physical states Ideal Mixing:

May 14, 2003 Curtis A. Meyer 44 Model for Mixing meson Glueball meson Glueball meson 1 r2r2 r3r3 flavor blind? r Solve for mixing scheme F.Close: hep-ph/

May 14, 2003 Curtis A. Meyer   Central Production WA102 Three States f 0 (1370) f 0 (1500) f 0 (1710) Overpopulation Strange Decay Patterns Seen in glue-rich reactions Not in glue-poor Glueball and Mesons are mixed. Scheme is model dependent. J/  Decays? Awaiting CLEO-c What about 2 ++ and 0  ? The Scalar Mesons Crystal Barrel proton-antiproton annihilation Scalar Mesons

May 14, 2003 Curtis A. Meyer 46 Decays of Glueballs? Glueballs should decay in a flavor-blind fashion.  ’=0 is true for any SU(3) singlet and for any pseudoscalar mixing angle. Only an SU(3) “8” can couple to  ’. Flavor-blind decays have always been cited as glueball signals.