recent results on quarkonium spectroscopy from babar and belle

Recent results onquarkonium spectroscopy

from BaBar and Belle

Bryan Fulsom

SLAC National Accelerator Laboratory

XXIIIiemes Rencontres de Blois

Blois, France

June 1, 2011

• Heavy quark (q=c,b) bound system: qq• Existence, masses, widths, quantum numbers• Phenomenological models, effective field theory, lattice QCD

Quarkonium Spectroscopy

BaBar/Belle Quarkonium Spectroscopy / Bryan Fulsom / Rencontres de Blois / 2011.06.01 / /26

The Experiments


• Operated over the past decade, accumulating ~1.5 ab-1

• Quarkonium production via B/(nS) decay, , ISR

• Decay of X(3872) J/– X(3872) mass, width and BF measurements

• Radiative decays of the X(3872)– Search for X(3872) J/ and (2S)

• Recoil against in (3S) b(2P)b(1P) transitions, (3S) mass, hb(1P) search

• Recoil against in (2S)

– First evidence for hb(1P)

• Bottomonium transitions with converted photons

– Radiative decays of (nS) and b(nP), b(1S) search

Topics covered today


Topics not covered today


X(3872)


• Discovered by Belle in B± X K±, X J/

– Since measured by BaBar, CDF, DØ, LHC– Also decays to DD*, J/, and – JPC assignment 1++ or 2-+

– DD* molecule, charmonium, or tetraquark?

• Mass, width, decays, rates can test these theories– Mass above or below DD* threshold? – Tetraquark predicts splitting between neutral and charged B decay

• Width– Narrow, best limit <2.3 MeV

• Decay rates– Ratio of neutral to charged (~1 for cc, ~0.1 for molecule)

X(3872)


• Full Belle dataset• Reconstruct B X(3872) K, X(3872) J/(l+l-)

• Perform 3D fit to mBC, E, m(J/ )

X(3872) J/ Update


• Most precise measurements of branching fraction and mass

• Mass splitting disfavors tetraquark hypothesis• BF ratio consistent with previous BaBar results

– R = (0.41 ± 0.24 ± 0.05)• Best limit on width• m(X(3872)) world average gives “binding energy” of ~0.12 ± 0.35 MeV

X(3872) J/ Results


Property Value

BF(B+K+X) x BF(XJ/ ) (8.6±0.8±0.8) x 10-6

BF(B0K0X) x BF(XJ/ ) (4.3±1.2±0.4) x 10-6

Ratio (B+/B0) 0.50±0.14±0.04

M = mX(B+) – mX(B0) -0.7±1.0±0.1 MeV

M(X(3872)) 3871.8±0.3±0.2 MeV

(X(3872)) <1.2 MeV

• BaBar evidence (~3.5) for X(3872) decaying to J/ and (2S)

• Analyze same decay channel with ~2x amount of data• Reconstruction

– J/ l+l-, (2S) l+l-, (2S) J/ final states

– Combine with to produce c1,2(1P) and X(3872) candidates

– Add K± or KS to form B± and B candidates

X(3872) J/, (2S)


• Verify signal extraction technique on B cJ K, cJ J/

• Good agreement with PDG

• First measurement of suppressed B± c2 K± decays

cJ J/


• Simultaneous fit of K± and KSo modes

• First “observation” (5.5) of X(3872) J/• Confirms C = + • Most precise measurement of branching fractions; agrees with BaBar

– B(B X(3872) K) B(X(3872) J/) = (1.8 ± 0.5 ± 0.1) 10-6

X(3872) J/


• Combine (2S)K with any ± or in the event and veto if it is consistent with B (2S)K* decay

• Fit (2S) distribution with three components:– Peaking (MC), non-peaking (sidebands/MC), signal

• No evidence for X(3872) (2S) signal– Ratio [X(3872) (2S)] / [X(3872) J/] < 2.1– Compared to R = 3.4 ± 1.4 from BaBar

X(3872) (2S)


Bottomonium


• Analysis goal: search for Y(3S) hb(1P)

• Define recoil mass: mR2 = (m(3S) – E

)2 – |P

|2

2 fit to mR

• Peaking components (3S) hb signal

(3S) (2S) (2S) (1S) b1,2(2P) b1,2(1P)

• Smooth backgrounds

– KS

– Non-peaking background

Dipion Recoil in (3S)


Dipion Recoil Fit Result


Dipion Recoil Summary


• Analysis Strategy

– Search for (3S) hb(1P)

– Reconstruct () +

– Require E consistent with hb(1P) b(1S)

– Assume B(hb(1P) b(1S)) 41%

• Define missing mass: m.m.()2 = (m(3S) – E)2 – P

2

– N from m fit in each m.m.() bin

2 fit of m.m.() distribution

– hb(1P) signal: Double Crystal Ball

– Background: 6th order polynomial

Search for hb(1P)


Y(3S)hb(1P)( b(1S))


• Measured mass agrees with expectation

– mhb(1P) = (mb0(1P)+3mb1(1P)+5mb2(1P)) / 9 9900 MeV/c2

• Branching fraction consistent with theory

• First evidence for hb(1P), definitively confirmed by Belle

Evidence for hb(1P)


Property Value

Yield 9145±2804±1082 evts.

Significance 3.0

M [hb(1P)] 9902±4±1 MeV/c2

BF(Y(3S)hb) x BF(hbb)

(3.7±1.1±0.7) x 10-4

• Radiative bottomonium transitions– Rates generally phenomenologically well-predicted

– Gateway to discovery (e.g.: (nS) b(1S))

• Use converted photons ( ee) improve resolution (e.g.: 25 5 MeV)

– Reconstruct pair of tracks, selected with 2fitter, m,

– Additional cuts: |costhrust|, Ntracks, veto

– Fit E* spectrum in four regions of interest

• Goals: Resolve E* spectrum to make precision measurements

Radiative Transitions


• Three “signal” transitions (bJ(2P) (2S)) and six (1D)-related lines

• Precision measurements of BF(bJ(2P) (2S))

(3S) : 180<E*<300 MeV


• Complicated photon spectrum: many overlapping signals

• Observation and precise measurement of (3S) b0,2(1P) transitions

• Transition rate pattern J = 2 > 0 > 1 unusual for quarkonium

(3S) : 300<E*<600 MeV


• Measure bJ(1P) (1S) and search for b(1S) signal

• Due to high bkgd/low eff., no evidence for (2S) b(1S)

(2S) : 300<E*<800 MeV


• Measure bJ(2P) (1S) and search for b(1S) signal

• E* for b(1S) is lower than expected, but significance is ~2.7

• Need more data to take full advantage of converted photon technique

(3S) : 600<E*<1100 MeV


• X(3872) at Belle– Improved measurements of X(3872) properties– Observation of X(3872) J/, disagreement on X(3872)

(2S)– Even after ~10 years, still haven’t solved the X(3872) problem!

• Bottomonium studies at BaBar

– Evidence for hb(1P) in Y(3S) hb(1P) decays

– Precision measurements of masses and dipion and radiative transitions offer important tests for theoretical models

• B-Factories have revitalized field of quarkonium spectroscopy– Many new measurements and discoveries of puzzling new states– Very promising future at Belle-II and SuperB

Summary


recent results on quarkonium spectroscopy from babar and belle

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