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Some Topics in Hadron Spectroscopy: Funny Things that Happen at Thresholds

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Some Topics in Hadron Spectroscopy:

Funny Things that Happen at Thresholds

Stephen Lars Olsen

Seoul National University

Constituent Quark Model

Gell-Mann

The model was proposed independently by Gell-Mann and Zweig in 1964 with three fundamental building blocks:

1960’s (p,n,l) Þ 1970’s (u,d,s):

mesons are bound states of a of quark and anti-quark:

Zwieg

baryons are bound state of 3 quarks:

Superseded by QCD in the 1970s:observed particles are color singlets

color + complementary color

white

white

3 primary colors

blue-yellow

green-magenta

red-cyan

Λ= (uds)

Mesons are color-anticolorpairs

Baryons are red-blue-green triplets

3

What about other color-singlet combinations?

Pentaquark: H-diBaryon

Glueball

Tetraquark mesons

qq-gluon hybrid mesons

Other possible “white” combinations of quarks & gluons:

u

d

u

d

s

_

u

tightly bound

6-quark state

S=+1 Baryon

d

s

u

s

d

Color-singlet multi-

gluon bound state

D0

_

c

_

u

loosely bound

meson-antimeson

“molecule”

c

tightly bound

diquark-diantiquark

u

_

p

_

u

c

_

_

u

_

D*0

c

_

_

c

c

1st evidence for non-qqmesons

The “light” scalar-meson nonet??

JP=0+

800

800

k+

k0

The “light” scalar mesons

980

980

a00

f0

a0-

a0+

980

s

600

_

k-

k0

800

800

light scalar nonet masses are inverted

scalars

pseudoscalars

unique

typical

Also:

- No “light” JP=1+ and 2+ partner nonets in the same mass range.
- In qq meson nonets, the I=0 state (here the a0(980)) has no s-quarks.
- m(f0(980))m(a0(980)) implies “ideal” mixing & small s-quark content in f0(980).

_

_

strong couplings of the a0(980) & the f0(980) to KK indicate strong OZI-rule violations

If not qq, then what?

Possibilities that have been suggested:

tightly bound diquark-diantiquark

loosely bound meson-antimeson

“molecule”

_

s

_

q

_

K

q

s

“nuclear” force

_

s

q

In color space:

_

p

_

q

s

K*

red+blue=magenta

(antigreen)

cyan+yellow=green

(antimagenta)

J.D.Weinstein & N.Isgur PRD 27, 588 (1983)

A colored diquark

is like a antiquark

A colored diantiquark

is like a quark

R.L.Jaffe PRD 15, 267 (1977)

a0(980)0 f0(980) mixing

N.N. Achasov, S.A. Devanin & G.N. Shestakov, Phys. Lett. B88, 367 (1979)

isospin violation enhanced by K0 – K+ mass difference

2mK+= 987.4 MeV

2mK0= 995.2 MeV

PDG2010:

Mf0= 980 ± 10 MeV

f0= 40 ~ 100 MeV

Ma0= 980 ± 20 MeV

a0= 50 ~ 100 MeV

2mK+

expect a narrow line shape:

G≈2(mK0-mK+)=7.8 MeV

2mK0

BES study of a0(980)0 f0(980) mixing

BESIII PRD 83, 032003 (2011)

a0(980)0 f0(980) mixing results

_

KK molecule model

90% CL upper limits

different models &

parameterizations

Statistics limited, but we should have lots more data soon

J/f0(980)p0,f0(980)pp

BESIII arXiv:1201:2737 (PRL) last week!

from helicity analyses

h(1405)

h(1405)

f0(980)+-

f0(980)00

f1(1285)

3.7s

f1(1285)

1.2s

1st observations: (1405)f0(980)p0

& J/ygf0(980)p0

Large Isospin violation:

Anomalous f0(980)lineshapein h(1405)f0(980)p0

BESIII arXiv:1201:2737

- Fitted mass:
- M”f0”= 989.9 ± 0.4 MeV
- ”f0”= 9.5± 1.1 MeV

The peak is midway

between 2mK0 & 2mK+

- & width ≈ 2(mK0 - mK+)

PDG2010:

Mf0= 980 ± 10 MeV

- f0=40 ~ 100 MeV

Effect of Triangle Singularity?

J.J.Wu et al, arXiv:1108.3772

Triangle Singularity (TS)

a0—f0 mixing

1405

1405

_

_

K*K and KK are on shell

enhancing TS contribution

and isospin violation

a0—f0 mixing is too small to

explain anomaly by itself

cc meson production in B decays

C+2/3

“Charmonium”

_

b-1/3

C-2/3

B0

W-

d1/3

_

S-1/3

“spectator”

K0

d1/3

Belle’s main purpose: Measure CP violations with B mesons that decay like this.

Nobel prize for Kobayashi &Maskawa in 2008

The X(3872) in BK p+p-J/y

discovered by Belle (140/fb)

PRL 91, 262001 (2003)

y’p+p-J/y

X(3872)p+p-J/y

M(ppJ/y) – M(J/y)

X(3872)p+p-J/y

recent results

LHCb

Belle

CDF

~6000 evts!

MX = 3871.61 ± 0.16 ± 0.19 MeV

MX = 3871.96 ± 0.46 ± 0.10 MeV

CDF: PRL 103 152001

MX = 3871.85 ± 0.27 ± 0.19 MeV

LHCb: arXiv:1112.5310

Belle: PRD 84 052004

What is known about the X(3872)

1) It has C=+1: X(3872)rJ/y and gJ/y are well established

XgJ/y’

Xp+p-J/y

rp+p- lineshape

BaBar PRL 102,132001

CDF: PRL 96 102002

1++

2- +

2) JPC = 1++ most likely

2-+ cannot be ruled out

c2 =4.60

c2=0.56

Belle: PRD 84 052004

c2 =1.56

c2=5.24

2-+ has higher c2 and fewer dof than 1++

What is known, continued

Nevts =4.2±7.8

B0X+K-

3) Isospin = 0, probably…

No (narrow) charged partners are seen;

limits are well below Ispin=1 expections

B+X+K0

no signal

Belle: PRD 84 052004

4) Xp+p-J/y (discovery mode), violates I-spin

1++ cc assignment? cc1

‘

pinned to:

Mcc2=3930 MeV

‘

- Mass is too low?
- 3872 vs 3905 MeV
- nr=2 splitting> nr=1

- Scaling the Bf(p+p-J/y)
- by cc theoretical value
- for G(gJ/y) gives:
- G(p+p-J/y)≈ 45 keV,
- ~100x larger than other
- cc Ispin violating widths.

_

3872 MeV

_

X(3872) mass(in p+p-J/ychannel only)

D0D*0 molecule??

_

D0

_

c

u

_

p

_

_

u

D*0

c

Isospin Violation in X(3872) decay:

- MD0+MD*0=3871.79 ± 0.30 MeV

MX(3872) –(MD0 + MD*0) = -0.12 ± 0.35 MeV

_

≈on mass shell

≈8MeVoff mass shell

MX(3872) –(MD+ + MD*-)= -7.74 ± 0.35 MeV

Consensus (?)

X(3872) is some kind of a mixture of

the cc1and a D0D*0 Molecule.

‘

_

D0D*0 molecule

_

D0

_

c

u

c

_

p

c

_

_

_

u

D*0

c

“(5S)” is very different from other states

Anomalous production of (nS)+-

Belle PRL100,112001(2008)

(MeV)

X10--2

Belle: G(4,5S)p+p-(1S)

(4S) (1S) p+p-

2S

3S

4S

(4S) (1S) p+p-

325±20 evts!

477 fb-1

23.6 fb-1

Belle: PRL 100 112001

52±10 evts

~1/20th the data

~1/5ththe cross-section

Belle: PRD 75 071103

Look at p+p-recoil mass in (5S)+-+ X

hb(1P)

X=(1S)

(2S)

hb(2P)

(3S)

121.4 fb-1

MM(+-) spectrum

hb(1,2P)JPC=1+-

1st observations

MM(+-) residuals

Belle: PRL 108 032001

hb(1,2P)

_

(bb) : S=0 L=1 JPC=1+-

January

Belle PRL 108, 122001

Expected mass (Mb0 + 3 Mb1 + 5 Mb2) / 9

MHF test of hyperfine interaction

Deviations from CoG of bJmasses

hb(1P)(1.6 1.5) MeV/c2

hb(2P)(0.5 +1.6 ) MeV/c2

-1.2

Agrees with expectations

Previous search

BaBar

3.0

(3S) → 0 hb(1P)

arXiv:1102.4565

G[(5S) hb(nP) +- ] is large

hb(2P)~85,000 evts

hb(1P)~50,000 evts

spin-flip

for hb(1P)

=

for hb(2P)

no spin-flip

Process with spin-flip of heavy quark is not suppressed

Mechanism of (5S) hb(nP) +- decay is exotic

Resonant structure of “(5S)” hb(nP)+-

MeV/c2

MeV

_

M1 =

MeV/c2

~BB* threshold

MeV/c2

MeV

1 =

MeV

_

_

~B*B* threshold

MeV/c2

M2 =

2 =

MeV

measure (5S)hb yield in bins of MM()

PHSP

PHSP

X

hc

M(hb(2P)+)

M(hb(1P)+)

non-res.~0

Dalitz distributions for events in Y(nS) signal regions.

9.43 GeV <MM(π+π-) < 9.48 GeV

10.05 GeV <MM(π+π-) < 10.10 GeV

10.33 GeV <MM(π+π-) < 10.38 GeV

Υ(1S)π+π-

Υ(3S)π+π-

Υ(2S)π+π-

max

M2(ϒπ±)

M2(π+π-)

M2(π+π-)

M2(π+π-)

To exclude contamination from gamma conversions we require:

M2(π+π-) > 0.16 GeV2

M2(π+π-) > 0.20 GeV2

M2(π+π-) > 0.10 GeV2

Belle PRL 108, 122001

(5S) (3S)+-

(5S) (2S)+-

(5S) (1S)+-

M(Υ(2S)π)max

M(Υ(1S)π)max

M(Υ(3S)π)max

M=1061143 MeV

M=1060923 MeV

M=1060823 MeV

Zb1

=22.37.74.0 MeV

=24.23.13.0 MeV

=17.63.03.0 MeV

M=1065212 MeV

M=1065763 MeV

M=1065123 MeV

Zb2

=8.42.02.0 MeV

=16.39.86.0 MeV

=13.33.34.0 MeV

Summary of parameter measurements

mB+mB*

2mB*

Zb(10610)

Zb(10650)

M=10607.22.0 MeV

M=10652.21.5 MeV

=18.42.4 MeV

=11.52.2 MeV

last month

Belle PRL 108, 122001

_

B-B* & B*-B* molecules??B

Zb(106050)±

Zb(106010)±

B*

b

b

b

_

_

b

_

_

B*

B*

_

_

B-B* “molecule”

B*-B* “molecule”

MZb(106010) –(MB+MB*) = + 3.6 ± 1.8 MeV

MZb(106010) –2MB* = + 3.1 ± 1.8 MeV

Slightly unbound threshold resonances??

M=10608.11.7 MeV

M=10653.31.5 MeV

Belle:

=15.52.4 MeV

=14.02.8 MeV

MB* + MB* = 10650.2 1.0 MeV

PDG: MB + MB* = 10604.50.6 MeV

1st: hb(1S) signals from hb(nP) hb(1S)

hb(1,2P)ghb(1S) are expected to be prominent (20%~50%)

g

Final state: p+p-gX

hb

hb

X

Bondar, Mizuk (Belle) ArXiv 1110.2251

hb(1P)ghb(1S)

measure hb yields in bins of MM(p+p-g)

(require 10.59<MM(p)<10.67 GeV, i.e. =MZb1,2)

Belle

-1.4

DMhfs(1S)=59.3±1.9+2.4 MeV

M[hb(1S)]=9401.0±1.9+1.4 MeV

G[hb(1S)]=12.4+5.5 +11.5MeV

-2.4

“ϒ(5S)”p+p-U(2S)

preliminary

-4.6 -3.4

hb(2P)ghb(1S)

Bf[hb(1P)ghb(1S)]=50+13 %

-9

“ϒ(5S)”p+p-hb(1P)

ϒ(2S)

hb(1S)

MM(p+p-g)

MM(p+p-)

Comparisons: hb(1S) results

PRL 101, 182003 (2008)

Bondar, Mizuk, et al (Belle)ArXiv 1110.2251

Belle

BaBar

hb(1P)ghb(1S)

-4.8

-1.4

ϒ(3S)ghb(1S)

PRD 81, 031104 (2010)

hb(2P)ghb(1S)

NRQCD

LQCD

CLEO

ϒ(3S)ghb(1S)

Reasonable agreement among

experiments and with theory

1st observation of the hb(2S)

hb(2P)ghb(2S) is expected to be the dominant decay mode (20%~50%)

g

Final state: p+p-gX

hb

hb

X

New!!!

Belle

hb(2P)ghb(2S)

measure hb(2P) yields in bins of MM(p+p-g)

(require 10.59<MM(p)<10,67 GeV, i.e. =MZb1,2)

DMhfs(2S)=24.3±3.5+2.8 MeV

-1.9

preliminary

M[hb(2S)]=9999.0±3.5+2.8 MeV

-1.9

Bf[hb(2P)ghb(2S)]=47.5±10.5+6.6 %

-7.7

MM(p+p-g)

Comparison: hb(2S) “signals”

Belle: IWHSS’12 April, 2012

Seth: Trento April 2012

ϒ(2S)ghb(2S)?

Belle:

CLEO

hb(2P)ghb(2S)

Bf[hb(2P)ghb(2S)]

about right

anomalously large

production rate

(~0.2✕cb1 rate)

MM(p+p-g)

strong disagreement with theory

agrees with theory

≈5σ discrepancy

LQCD predictions for DMhfs(1,2S)

DMhfs(1S)

DMhfs(2S)

BaBar/CLEO

DMhfs(1S)

Belle

CLEO

Belle

Meinel PRD82, 114502 (2010)

DMhfs(2S)

Belle

cc

Belle

HP-QCD PRD85, 054509 (2012)

m2

p

BESIII c(2S)g (KsK+p-)

106M

BESIII preliminary

y’

M1

E1

hc(2S)

cc1

cc1

hc(2S)

BF(y’ghc(2S))

= (4.7±0.9±3.0)×10-4

BESIII preliminary

BF(y’gcc1)= 9.2±0.4%

PDG

y’ghc(2S) yield ≈ 0.005 y’-gcc1 yield

Same M1 vs E1 suppression applies to bb

_

Summary

-- open strange threshold --

_

- Strong evidence for KK-mediated a0(980) f0(980) mixing reported by BESIII
- -below level expected for “pure” KK molecule picture
- Large (≈20%) Isospin violation seen in h(1405)p0f0(890) decays
- anomalous f0(980) width influence of KK* threshold & Triangle Singularity
- Properties of X(3872) consistent with expectations for DD* S-wave molecule-like state
- - JPC=1++ favored (2-+ not ruled out) mixing with cc1?
- - Mass = MD0 + MD*0 to a part in ~104
- - no isospin partners are seen
- - Isospin-violating X(3872)rJ/y is a strong decay mode
- “ϒ(5S)”Zb1,2p- with Zbϒ(nS)p+ &Zbhbp+ a source of p+p-ϒ(nS) & p+p-hb(nP) at “ϒ(5S)”
- - MZb1-( MB + MB* ) = +3.6 ±1.8 MeV; MZb2- 2MB* = +3.1 ±1.8 MeV
- S-wave BB* and B*B* molecules?large widths to hidden beauty
- First observation of hb(2S)
- - DMhfs(2S) = 24.3±4.3 MeV Bf[hb(2P)ghb(2S)] = 47±13% preliminary
- no surprises

_

_

-- open charm threshold --

_

‘

_

-- open beauty threshold --

+

+

+

_

_

_

-- new from Belle --

K+K-

BESII PLB 607, 243 (2005)

f’2(1525)+f0(1710) K+K-

f0(980) K+K-

strong f0(980)

coupling to KK

_

f0(980) p+p-

gKK

gpp

=4.2±0.3

f2(1270)+f0(1370) p+p-

f0(1790) p+p-

Bf(J/yff0(980) = 0.32±0.09 x 10-3

Signal for a0(980)K+K-

Belle Collab:

PRD 80, 032001 (2009)

gghp0 Belle

a0

Crystal Barrel Collab: PRD 57, 3860 (1998)

hp0

a0(980) K+K-

a0(980) (hp0)

a0(1320) (hp0)

strong a0(980)

coupling to KK

gKK

gph

=1.03±0.14

p+p-system in X(3872)p+p-J/y comes from rp+p-

Belle: PRD 84 052004

CDF: PRL 96 102002

rp+p- lineshape

M(p+p- )

p+

r

p-

X3872

J/y

M(p+p- )

JPC of the X(3872)

1++ fits well with no adjustable parameters

2-+cannot be ruled out

m+

qm

J. Rosner PRD 70, 092023 (2004)

for 1++:

p-

K

c

p+

CDF: PRL 98 132002

m-

1++

Belle: PRD 84 052004

2- +

1++

2- +

1- -

c2 =4.60

c2=0.56

O++

c2 =1.56

c2=5.24

2-+ has higher c2 and fewer dof than 1++

1++ cc assignment? cc1

‘

pinned to:

Mcc2=3930 MeV

‘

- Mass is too low?
- 3872 vs 3905 MeV
- nr=2 splitting> nr=1

- G(cc1 gy’) ~180 keV
- G(cc1 g J/y) ~14 keV
- G(cc1 gy’)/G(cc1 g J/y)>>1
- expt’l upper limit: <2.1

‘

‘

T.Barneset al PRD 72, 054026

- Gp+p-J/y=(3.4±1.2)GgJ/y ~45 keV

huge for Isospin-violating decay

c.f.: G(y’p0J/y)≈0.4 keV

Does the X(3872) have Ispin=1?

search for charged partners: X+(3872)p+p0J/y : Isospintriplet?

Isospin relations:

2-dim fits:

Nevts =4.2±7.8

B0X+K-

B(B0K-X+)xB(X+p+p0J/y)<3.9 x10-6

Rule out isospin triplet model

B+X+K0

no signal

B(B+K0X+)xB(X+p+p0J/y)<4.5x10-6

not 2x larger!!

BEPCII storage rings

Beam energy: 1.0 - 2.3 GeV

Peak Luminosity:

Design:1×1033 cm-2s-1

Achieved:0.65x1033cm-2s-1

Beam energy measurement: Using Compton backscattering technique. Accuracy: dEbeam/Ebeam ≈ 510– 5

dEbeam ≈ 50 KeV @Ebeam ≈ mt

BESIII Collaboration

Helmholtz Institute Mainz

Johannes Gutenberg-University Mainz

11

Turkey: Turkish accelerator center

29

>300 physicists

49 institutions from 10 countries

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