Quarkonium experimental overview I Stephen Lars Olsen Seoul National University France-Asia Particle Physics School, Les Houches, FRANCE October 11-12, 2011
Outline J/ ψ ψ ’ (1S) ψ ” (4S) Lecture 1: Bound charmonium & bottomonium states and their properties
Outline X(3872) Z b (10610) Y(3940) Y(4260) Z b (10650) Lecture 2: Non-quarkonium, quarkonium-like states and the future
Lecture 1 Bound charmonium & bottomonium states and their properties
Constituent Quark Model 1964 The model was proposed independently by Gell-Mann and Zweig Three fundamental building blocks 1960’s ( p , n , λ ) ⇒ 1970’s (u,d,s) − π = ( u d ) mesons are bound states of a of quark and anti-quark: Can make up "wave functions" by combining quarks: π + = ud, π - = du, π o = 1 2 (uu - d d), k + = d s, k o = ds baryons are bound state of 3 quarks: proton = (uud), neutron = (udd), Λ = (uds) Λ = (uds) anti-baryons are bound states of 3 anti-quarks: p = u n = u d Λ = u u d d d s 5
Make mesons from quark-antiquark Y Y = “hypercharge” = S+B Y _ _ _ us s ds d u _ +1/3 _ _ _ _ _ _ dd _ du uu ud u d _ I Z ss s _ _ sd su -2/3 _ ⊗ = ⊕ -1/2 +1/2 3 3 1 8
Ground state mesons (today) J P =0 - J P =1 - 498 494 892 896 K* 0 K* + 135 548 783 776 776 776 ρ - ω ρ 0 ρ + 139 139 φ 958 1020 _ 494 498 K* - K* 0 896 892 ( π + , π 0 , π - )=lightest ( ρ + , ρ 0 , ρ - )=lightest n r =0 n r =0
HW: Construct baryon octet and decuplet combinations of three uds triplets duu d uuu u d u d u s uus s s Finish the procedure
Answer 2(8-tet)s + 10-plet ⊕ singlet dud uud ddd uud dud uud sdd sud suu sdd sud suu sud ssd ssd ssu ssu sss ⊗ ⊗ = ⊕ ⊕ ⊕ 3 3 3 1 8 8 10
Ground state Baryons J P =1/2 + J P =3/2 + 939 938 M=1232 MeV 1115 M=1385 MeV 1189 1197 1192 M=1533 MeV 1315 1321 M=1672 MeV all n r =0 all n r =0 10
Are quarks real objects? or just mathematical mnemonics? 기억하는 助记符 Are quarks actually real objects?" Gell-Mann asked. "My experimental friends are making a search for them in all sorts of places -- in high-energy cosmic ray reactions and elsewhere. A quark, being fractionally charged, cannot decay into anything but a fractionally charged Gell-Mann object because of the conservation law of electric charge. Finally, you get to the lowest state that is fractionally charged, and it can't decay. So if real quarks exist, there is Nobel an absolutely stable quark. Therefore, if any were ever Prize made, some are lying around the earth." 1969 But since no one has yet found a quark, Gell-Mann concluded that we must face the likelihood that quarks are not real.
A prediction of the quark model: - e hadrons - σ q Σ lowest ≡ ( ) ( ) ( ) q e + order = + + = µ - 2 2 2 2 2 2 1 1 = Q f R e - 3 3 3 3 flavor σ color µ + e +
Mark I detector At SLAC’s “SPEAR” e + e - collider muon identifier tracking chamber e + e - ~3GeV
R data in June 1974 hadrons R e + E cm e - 2/3 E cm Compilation by: L. Paoluzi Acta Physica Polonica B5, 829 (1974)
after a fine energy scan near 3 GeV: A huge, narrow peak near 3.1 GeV Also seen in pN e + e - X ψ at Brookhaven J R=2.2 M(e + e - ) >>2/3 10 J.J. Aubert et al., PRL 33, 1404 (1974) The “J / ψ ” meson J.E. Augustine et al., PRL 33, 1406 (1974)
Another peak near 3.69 GeV ψ ’ About 2 weeks later G.S. Abrams et al., PRL 33, 1453 (1974)
Why J/ ψ ? Group leader of the Event in Mark I Brookhaven expt ψ ’ π + π - J/ ψ e + e - Samuel C.C. Ting Mark-I detector Chinese character for Ting:
Interpretation of J/ ψ and ψ ’ charmed-quark anticharmed-quark mesons c c c c n r =1 n r =0 M=3.686 GeV M=3.097 GeV charmed quark q= +2/3 partner of the s-quark + + + 2 2 2 u c ? 3 3 u 3 A q=+2/3 rds partner before 1974 after 1974 of the s quark had − − − − 1 1 1 1 d s been suggested by 3 s 3 d 3 3 many theorists
Charmonium mesons formed from c- and c-quarks r c c c-quarks are heavy: m c ~ 1.5 GeV ≈ 2m p velocities small: v/c~1/4 non-relativistic, undergraduate-level QM applies
QM of cc mesons c c r 2 − ∇ Ψ + Ψ = Ψ 2 ( ) V r E 2 m r What is V(r) ?? “derive” from QCD
“Cornell” potential c c r V(r) linear “confining” long distance ~0.1 fm component r 1/r “coulombic” short distance component 2 parameters: slope & intercept
_ Charmonium (cc) Positronium (e + e - ) ψ ’ J/ ψ
The “ABC’s” of charmonium mesons r r J PC quantum numbers S S 1 2 r r r r S = 1 + c S S c c S=1 triplet of state L 2 r r r S=0 singlet J = L + S P = ( − 1) L + 1 Parity (x,y,z) ↔ (-x,-y,-z) C-Parity quark ↔ antiquark C = ( − 1) L + S J/ ψ ( ψ ’ ): photon: J PC = 1 - - J PC = 1 - - e + X J/ ψ ( ψ ’ ) e -
ABC’s part II spectroscopic notation r r S S r r r 1 S = 1 + 2 S S r c 2 c c r r r L J = L + S ψ ’ = 2 3 S 1 η c = 2 1 S 0 ’ S= spin (0 or 1) J= total ang. mom. (2S+1) L J n J/ ψ = 1 3 S 1 n=radial quant. nmbr L= S, P, D, F, … η c = 1 1 S 0 0, 1, 2, 3, …
ABC’s part III “wave function at the origin” _ In J/ ψ decay, the c and c quarks S-wave have to annihilate each other n=1 e + α c c S-wave e - ψ ( r → 0) ∝ r n=2 P-wave This only can happen when they are very near each other: S-wave Many J/ ψ processes are ∝ | Ψ (0)| 2 , P-wave the “wave function at the origin,” ψ ( r → 0) ∝ r 2 D-wave or, in the case of states with Ψ (0)=0, n=3 derivatives of Ψ (0), which are usually small.
Immediate questions: • Can the other meson states be found? • Why are the J/ ψ and ψ ’ so narrow?
Finding other states These states have been identified ψ ’ = 2 3 S 1 χ c2 = 1 3 P 2 c χ c1 = 1 3 P 1 r c c L = 1 χ c0 = 1 3 P 0 c c c r L = 0 J/ ψ = 1 3 S 1
The Crystal Ball Detector
E-dipole γ transitions to 1 3 P 0,1,2 e + ψ ’ e - QM textbook formula: α 3 E ∑∫ 2 γ Γ = Ω Ψ ε ⋅ Ψ d r γ π E 1 f i 3 2 2 c λ e - ψ ’ 24. 29. 26. 24. 313. 239. 114. J /ψ E. Eichten et al., PRL 34, 369(1975)
Crystal ball results ψ ’ γ X e + ψ ’ e - ψ ’ Crystal Ball expt: Phys.Rev.D34:711,1986 . E γ “smoking gun” evidence that quarks are real spin=1/2 objects J /ψ
ψ ’ γχ c0 radiative transition Expect 1+cos 2 θ BESII PRD 70, 092004 (2004)
Discovery of the P-wave states ( χ c0,1,2 ) convinced everyone quarks were real e - ψ ’ E γ J /ψ Crystal Ball expt: Phys.Rev.D34:711,1986 .
Immediate questions: • Can the other meson states be found? • Why are the J/ ψ and ψ ’ so narrow?
Problems with the quark model: • Individual quarks are not seen • why only qqq and qq combinations? • violation of spin-statistics theorem?
Ω − s -1/3 s -1/3 s -1/3 three s-quarks in the same quantum state Das ist verboten!!
The strong interaction “charge” of each quark comes in 3 different varieties Y. Nambu M.-Y. Han Ω - s -1/3 s -1/3 1 2 s -1/3 3 the 3 s -1/3 quarks in the Ω - have different strong charges & evade Pauli
Attractive configurations Baryons: Mesons: ε ijk e i e j e k i j i δ ij e i e j j k i ≠ j ≠ k same as the rules for combining colors to get white : add 3 primary colors -or- add color+complementary colo r quarks: e i e j e k color charges antiquarks: anticolor charges e i e j e k ε ijk e i e j e k δ ij e i e j
Quantum Chromodynamics e r QED: scalar charge e QCD triplet charge: e b e j e g α QED α s Non-Abelian g ij extension of QED single eight e i photon “gluons” QCD gauge transform QED gauge transform ∇ ∇ + i α λ i G i ∇ ∇ + i e A 8 vector 1 vector eight 3x3 SU(3) fields field matrices (gluons) (photon)
Vacuum polarization QED vs QCD QED 2n f QCD 11C A in QCD: C A =3, & this dominates α s increases with distance
QED: photons have no charge coupling decreases at large distances QCD: gluons carry color charges gluons interact with each other coupling increases at large distances α Coupling strengths distance
Test QCD with 3-jet events (& deep inelastic scattering) α s gluon rate for 3-jet events should decrease with E cm
“running” α s α s ~1/4 short distance Large distance M J/ ψ
Color explains the discrepancy in R - e hadrons - σ q [ ] Σ ( ) ( ) ( ) lowest ≡ = + + = q 2 2 2 e + order 2 1 1 µ - 3 2 2 = Q f R e - 3 3 3 flavor σ & color color µ + e + Each quark has 3 colors
J /ψ R=2.2 >>2/3 [ ] ( ) ( ) ( ) = + + ≈ 2 2 2 2 1 1 R 3 2 . 2 10 3 3 3
why are the J/ ψ and ψ ’ so narrow? 2 3 4 E cm
Recommend
More recommend
