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NTU colloquium June 11, 2007 S.L. Olsen U of Hawai’i 高能所 北京
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X3872 X1835 Y4260 Stephen L. Olsen University of Hawai’I & 高能所 北京 Homeless mesons
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Constituent Quark Model: 1964 (& 3 antiquarks) Mesons: qq p: u +2/3 p: u -2/3 +:+: d -1/3 u +2/3 d +1/3 u -2/3 d +1//3 u +2/3 -:-: u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3 Gell-Mann 3 quarks Zweig Baryons: qqq
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Constituent Quark Model: 2007 (& 6 antiquarks) Mesons: qq c:c: c +2/3 c:c: u -2/3 + : s -1/3 s +1/3 d +1/3 c -2/3 u -2/3 b +1//3 u +2/3 - : b -1/3 u -2/3 b +1/3 t -2/3 c +2/3 b -1/3 t +2/3 6 quarks Baryons: qqq u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3
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but… quarks are not seen why only qqq and qq combinations? What about spin-statistics?
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Fabulously successful at bringing order to the hadron “zoo” mesons baryons q q q q q
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s -1/3 three s-quarks in the same quantum state Das ist verboten!!
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The strong interaction “charge” of each quark comes in 3 different varieties Y. Nambu O. Greenberg s -1/3 the 3 s -1/3 quarks in the - have different color charges & evade Pauli --
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QCD: Gauge theory for color charges generalization of QED + i e A + i i G i QED gauge Xform QCD gauge Xform eight 3x3 SU(3) matrices 8 vector fields (gluons) 1 vector field (photon) scalar charge: e isotriplet charge: erebegerebeg QED QCD Yang Mills Nambu Fritzsch & GellMann
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Attractive configurations ijk e i e j e k i ≠ j ≠ k ij e i ejej same as the rules for combining colors to get white : add 3 primary colors or add color+complementary color antiquarks: anticolor charges Hence the name: Quantum Chromodynamics quarks: e i e j e k color charges ejej eiei ekek
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Difference between QED & QCD QED: photons have no charge QCD: gluons carry color charges gluons interact with each other Coupling strengths distance
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Test QCD with 3-jet events (& deep inelastic scattering) rate for 3-jet events should decrease with E cm gluon ss
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“running” s Why are these people smiling?
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Running as tests QCD at short distances only distance The long-distance regime, where the matter we are made of exists, remains untested.
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Are there other color-singlet spectroscopies? Pentaquarks: e.g. an S=+1 baryon (only anti-s quark has S=+1) Glueballs: gluon-gluon color singlet states Multi-quark mesons: qq-gluon hybrid mesons uc u c cc u d u s d Non-quark model states expected in QCD
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Pentaquarks “Seen” in many experiments BaBar CDF but not seen in just as many others High interest: 1 st pentaquark paper has ~720 citations Belle BES
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Experimental situation is messy (some contradictory experiments) SAPHIR (2004) 4.8 M(nK + )(GeV) Counts/4 MeV nKKγp s CLAS (2005) Same reaction
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Some groups contradict themselves 5.2 CLAS-D (2003) no signal CLAS-D (2005) ??? d+K-K+nd+K-K+n
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Pentaquark Scoreboard Positive signals Negative results Also: Belle Compass L3 CLAS Yes: 17 No: 18
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PDG 2006 “The conclusion that pentaquarks in general, and the in particular, do not exist, appears compelling.” - George Trilling LBL
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This is a risky business You never know if nature is smiling at you or something else
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This talk: evidence for non-qq mesons cc uc u c 4 (& 6) quark states “hybrid” qq-gluon states
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The Beijing Electron Positron Collider (BEPC) e+e+ e-e- 高能物理研究所
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Beijing Spectrometer (BES)
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e + e - annihilation cross section s c b E cm (GeV) q q BES Energy Range
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J/ pp C -2//3 c +2/3 u +2/3 u -2/3 d -1/3 u +2/3 d +1/3 u -2/3 p p
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J/ pp This is the c, pp the J/ ’s spin=0 partner What is this??? M(pp) GeV
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Fit the M(pp) distribution Best fit to this peak is a resonance with peak mass below the pp mass threshold M=1835 MeV no know 100MeV resonance
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Actual fit M=1830.6 ± 6.7 MeV/c 2 < 153 MeV/c 2 (90% CL) J/ pp in the BES expt 00.10.20.3 2 /dof=56/56 fitted peak location
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A pp bound state (baryonium)? p npp deuteron: loosely bound 3-q 3-q color singlets with M d = 2m p - baryonium: loosely bound 3-q 3-q color singlets with M b = 2m p - ? attractive nuclear force attractive force? There is lots & lots of literature about this possibility
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An old idea
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Fermi & Yang in 1949 (7 years before p discovery): If NN potential is attractive, they could bind to form -like states.
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Expectation for pp bound state meson m p +m p Above threshold X pp ~100% below-threshold p and p annihilate to mesons I=0, J PC =0 -+ init. state: pp ’ is common
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Look in J/ ’ M( ’) M=1833 MeV 70MeV m p +m p
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X(1835): “6-quark” meson? u +2/3 u -2/3 d -1/3 u +2/3 d +1/3 u -2/3 3 quarks + 3 antiquarks Need to confirm J PC of the ’ peak is 0 -+ Need to find it in other common 0 -+ pp annihilation channels
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Move over to Japan Tsukuba Mountain KEK laboratory KEKB Collider
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Belle Expt
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e + e - annihilation cross section s c b E cm (GeV) q q KEK B-factory
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Primer on Charmonium
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B meson decays u -2/3 b -1/3 C -2/3 C +2/3 u -2/3 S -1/3 W-W- K-K- “Charmonium”
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Charmonium r mesons formed from c- and c-quarks c-quarks are heavy: m c ~ 1.5 GeV 2m p velocities small: v/c~1/4 non-relativistic QM applies cc
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QM of cc mesons cc r What is V(r) ?? “derive” from QCD quantum chromodynamics
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“Cornell” potential ~0.1 fm G.S.Bali hep-ph/0010032 “confining” large distance component slope~1GeV/fm 1/r “coulombic” short distance component cc r V(r) 2 parameters: slope & intercept
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Charmonium spectrum All of these states are well established J/ ’’ cc c’c’ c ’’ hchc
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Study B K - J/ u -2/3 b -1/3 C -2/3 C +2/3 u -2/3 S -1/3 W-W- look here J KK
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The X(3872) B K J/ M( J ) – M(J/ ) ’ J/ X(3872) J/ S.K. Choi et al PRL 91, 262001
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Its existence is well established seen in 4 experiments X(3872) CDF X(3872) D0 hep-ex/0406022 9.4 11.6
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Is it a cc meson? These states are already identified 3872 MeV Could it be one of these?
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Determine J PC quantum numbers of the X(3872) with minimal assumptions
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C=+1 is established X(3872) J/ seen in: & Belle PRL 96 102002 M( looks like a X(3872) ” ”J/ seen CDF Belle hep-ex/0505037
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Use Angular Correlations to determine J & P K J/ e e J=0 X 3872 J z =0 z Rosner (PRD 70 094023) Bugg (PRD 71 016006) Suzuki, Pakvasa (PLB 579 67)
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ll |cos l | 2 /dof = 34/9 |cos | |cos | 2 /dof=34/9 0 ++ 0 -+ rule out 0 ++ & 0 -+ J k x J Ruled out by Belle
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Angular analysis from CDF CDF Collab. PRL 98, 132002 (2007) 1 ++ or 2 -+
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Possible J PC values 0 -- exotic violates parity 0 -+ ( c ” ) 0 ++ DD allowed ( c0 ’ ) 0 +- exotic DD allowed 1 - - DD allowed ( (3S)) 1 -+ exotic DD allowed 1 ++ ( c1 ’ ) 1 +- (h c ’ ) 2 - - ( 2 ) 2 - + ( c2 ) 2 ++ DD allowed c2 ’ ) 2 +- exotic DD allowed 1 ++
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can it be a 1 ++ cc state? 1 ++ c1 ’ (the only charmonium possibility) 3872 X J/ decay is isospin-violating for a 1 ++ cc state (Isospin violating) M=3872 MeV is too low, especially now that we know that M( c2 ’ )=3931 4 MeV The (X J/ ) partial width is expected to be 30~40 x (X J/ experimentally it is ~1/10th Allowed E1 transition
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Intriguing fact M X3872 =3871.2 ± 0.5 MeV m D0 + m D0* = 3871.6 ± 0.4 MeV lowest mass charmed meson lowest mass spin=1 charmed meson DD* 2 loosely bound qq color singlets with M = m D + m D* - u c u c one exchange attractive for 1 ++ Tornqvist PLB 590, 209 (2004) Braaten et al, PRL 93, 162001 Deuson? deuteron-like DD* bound state?
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DeRujula, Georgi,Glashow, PRL 38, 317 (1977) X(3872)??
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X(3872) = D 0 D* 0 bound state? J PC = 1 ++ is favored M ≈ m D0 + m D0* Large isospin violation is natural ( & was predicted) : |D 0 D* 0 > = 1/ 2 (|10> - |00>) (X J/ ) < (X J/ ) was predicted (X D 0 D 0 0 ) too large? Bf(B 0 K 0 X 3872 )/Bf(B + K + X 3872 ) too large? Equal mixture of I=1 & I =0 Swanson PLB 598, 197 (2004) Tornqvist PLB 590, 209 (2004) Swanson PLB 588, 189 (2004) Braaten & Kusunoki PR D71, 074005 predict: < 0.08 BaBar measurement (hep-ex/0507090): 0.5 0.3
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X(3872) summary –Existence well established –J PC = 1 ++ (probably) –Br(X J/ ) too high for charmonium –Br(X D 0 D 0 0 ) too high for molecule –Mass too low for hybrid Four years after discovery, theorists are still puzzling over what it may be
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Next, California Stanford Linear Accelerator Ctr BaBar Detector
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Radiative return s c b E cm (GeV) 10.58 GeV B-factory energies 3~5 GeV
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J/ sideband Well above DD & DD* threshold but wide & found in a suppressed mode?? M=4259 8 MeV = 88 23 MeV B. Aubert et al. (BaBar) hep-ph/0506081 Y(4260) 10.58 GeV 4.26 GeV not seen in (e + e - hadrons) at Ecm =4.26 GeV J.Z. Bai et al. (BESII) PRL 88 101802 BES BaBar’s Y(4260) (e + e - hadrons)
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No 1 -- cc slot for the Y(4260) 4260 X.H. Mo et al, hep-ex/0603024 J.Z. Bai et al. (BESII) PRL 88 101802 No place for it!
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If not charmonium, what? cc “hybrid” cc-gluon state? But why does it decay to J/ , and not to D and D* mesons?
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Y(4260) summary – Existence well established – J PC = 1 -- – (X J/ ) too high for charmonium – Br(X D ( * ) D ( * ) ) too low for hybrid Another mystery!!
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Concluding remarks Pentaquarks are dead (at least for now) A number of “mysterious” mesons have been found Are these curiosities? or 1 st signs of new hadron spectroscopies? Hopefully, time, & more experimentation, will tell
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謝謝
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Thank you
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Back-up slides
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Conclusion either: –The constituent quark model for mesons needs major revision or: –There is a new, non-qq, hadron spectroscopy, maybe more than one.
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Difference between QED & QCD QED: photons have no charge QCD: gluons carry color charges gluons interact with each other
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QCD: Gauge theory for color charges generalization of QED + i e A + i i G i QED gauge Xform QCD gauge Xform eight 3x3 SU(3) matrices 8 vector fields (gluons) 1 vector field (photon) scalar charge: e isotriplet charge: erebegerebeg QED QCD Yang Mills Nambu Fritzsch & GellMann
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Vacuum polarization QED vs QCD 2n f 11C A in QCD: C A =3, & this dominates
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QED QCD difference Coupling strength distance
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Test QCD with 3-jet events (& deep inelastic scattering) rate for 3-jet events should decrease with E cm gluon ss
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“running” s
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3872 quark-antiquark chalet No rooms left Fussy! x1835 Y4260 Looking for a home:
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3872 rats! Molecule Manors DD x1835 Y4260
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3872 Hydrid heaven M<4.4 GeV need not apply Fat Cats! x1835 Y4260
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Other hadronium states? M=1859 MeV/c 2 < 30 MeV/c 2 (90% CL) J/ pp in the BES expt M(pp)-2m p (GeV) 00.10.20.3 acceptance 2 /dof=56/56 fitted peak location +3 +5 10 25 J.Z.Bai PRL 91,022001(2003)
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Charmonium state? (e + e - hadrons) No sign of it (e + e - hadrons) at Ecm =4.26 GeV BES 4260 J.Z. Bai et al. (BESII) PRL 88 101802 No place for it!
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DD** threshold in relation to the “Y(4260)” 4.28-m D D** spectrum M( J/ ) GeV No obvious distortions
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it likes to decay to pp if it can Decays to mesons Decays to pp
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A pp bound state (baryonium)? p npp deuteron: loosely bound 3-q 3-q color singlets with M d = 2m p - baryonium: loosely bound 3-q 3-q color singlets with M b = 2m p - ? attractive nuclear force attractive force? There is lots & lots of literature about this possibility E. Fermi, C.N. Yang, Phys. Rev. 76, 1739 (1949) Y.Nambu, G. Jona-Lasinio Phys Rev 122, 345 (1961) … I.S. Shapiro, Phys. Rept. 35, 129 (1978) C.B. Dover, M. Goldhaber, PRD 15, 1997 (1977) … A.Datta, P.J. O’Donnell, PLB 567, 273 (2003)] M.L. Yan et al., hep-ph/0405087 B. Loiseau et al., hep-ph/0411218 … These are very famous papers !!!
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The X(3872) ???? Study J/ produced in B K J/ decays
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hadronic molecules a new spectroscopy? may be more particles to find
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summary X(1835): – Existence well established – J PC = 0 -+ – Br(X pp) too high for qq meson – X ’ is expected for sub-thresh pp state
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