The meson landscape

The meson landscape

Scalars and Glue in Strong QCD

New states beyond

Weird baryons: pentaquark problems

“Diquarks,Tetraquarks, Pentaquarks and no quarks”

Some reflections on Pentaquarks

Correlated Colour in Strong QCD

Implications for Exotic Mesons?

Frank CloseIPPP 041027

“Diquarks,Tetraquarks, Pentaquarks and no quarks”

Colour Correlations in Chromostatics

+ ++

baryon

Chromostatics: Like electrostatics – unlike colours attract

+- meson

+ +

Attraction of two quarks to make a “diquark”

If this acts as a quasi-particle………

“Scalar Diquarks”

Pauli maximal attraction when net spin=0 and different flavours

+ + - -

Diquark antidiquark mutually attract ………

……Making a meson from diquarks = 2 quarks and 2 antiquarks

+ +

- -

Fall apart into qq* pairs: Broad width

Flavour pattern in nonet differs from qq*Consistent with light scalar mesons Jaffe; Close Tornqvist; Maiani et al

+ + + +

+ +

Three diquarks……..

+ + + ++ +

rearrange to make…e.g. a deuteron

(lower energy state…… presumably)…

…..not obvious in JW model with light [ud]

+ + + +

-

Lets try another way: replace the BLUE YELLOWDiquark by a RED antiquark

YELLOW

+ + + +

-

+ + + +-

d d u us*

neutronKThe forces rearrange them to makee.g. a neutron and a kaon… “fall apart” = broad

Or so we thought!!!2002 discovered a (narrow) pentaquark!

maybe

+ + + +

-

d u d u

s*

If the data survive; and if this is a pentaquark….the correlations seem to maintain their identities100 times more stable than anticipated (expt)= two ideas on how this happens (theory)Jaffe Wilzcek Karliner Lipkin

(qq)q(qq) description (Jaffe, Wilczek)

JP = ½+

L=0

(ud)

(ud)s

L=1

Colour correlated models of the + Pentaquark

(qqq)(qq) description (Karliner, Lipkin)

JP = ½+

L=1

(uds)

(ud)

distance > color magnetic force

u d u d

Q*

u d

Jaffe Wilczek

ud udQ*

Karliner Lipkin

L=1

L=1

Diquark attractionsfor unlike flavours = basis for pentaquark models( not demonstrated how low mass scalar diquarks form, stability, effective bosons, consistency with other hadron spectroscopy… etc. = ?)

Narrow Pentaquarks(if they exist)= strong QCDcorrelations

Some reflections on Pentaquarks

10

Inconsistencies (I)

• Width of Θ+(1540)– Two “positive” experiments:

HERMES: ΓΘ = 17 9 2 MeV ZEUS: ΓΘ = 8 4 MeV

– K+N PWA results indicates ΓΘ < 1 MeV

• Mass of Θ+(1540)

(LEPS)

nK

Anomalies with Theta Mass?

0SpK

F. Close and Q. Zhao, hep-ph/0404075

ArndtBuccellaCarlsonDyakanovEllisFaberGianniniHuangInoueJaffeKarlinerLipkinMaltmanNussinovOhPolyakovQiangRosnerStechTrillingUVenezianoWilczekXiangYangZhu

If Theta doesn’t exist,then these (and many other theorists)should be congratulated on their creativity

Mass

15

Mass Fitted historically. Not calculated

Dyakanov Petrov Polyakov DPP assumed N(1710) in 10bar

Jaffe Wilzcek JW assumed N(1440) as (ud)(ud)dbar

X mass formula bizarre: q_5 10bar mass gap 1/3 m_s X pure 10bar not photoproduced from p

X width 300MeVX gamma n:gamma p = radial 56plet qqqX Delta(1670) partner

Karliner Lipkin KL assume cs* 200MeV orbital to set scale

X spin averaged cs* costs 500MeV, Theta= 1800MeV

Mass

(L=1) = 200MeV Karliner Lipkin

2.592.56

2.32

2.11

1.97

1-

0+

Ds(cs*) spectrum

210

Ask Harry: is this cs*or DK molecule?

Mass

400-480

1-

0+

0-

1+

L=0

L=1

2+

2.55 -2.47

2.07

Spin averaged masses in multiplet

Theta = 1750-1830

u d u d

Q*

u d

Jaffe Wilczek

ud udQ*

Karliner Lipkin

L=1

L=1

3/2

1/2<100MeV FC+ Dudek

10bar 3/2+ unique to qqqqq*

Spin-Orbit splitting

Mass Fitted more recently or excused

Weise…Wilczek…Close…Maiani…(Kochelev,Vento) m[ud] ~ m(d) ~ 300MeV

e.g. L=2: N(1680: [ud] u) = rho_3(1700: d*u)e.g. L=1: Lambda(1405: [ud] s) = K_2(1430: ds* )

0+ mesons \sigma 600MeV; k 800MeV; f0/a0 980MeV

X doesn’t explain Lambda

Theta ~ 1100 + orbital;

Why (does?) [ud] get protected ….at high L… in S-wave mesonsBut not in S-wave baryons?

ud udQ*

udQ* uds* compact stabilised by instanton forces.aids narrow width (assertion)(ud)6,1 and (ud)3,0 mix lowers mass Hogaasen Sorba; Kochelev Vento……..

ud*Q ud* leaks into pions = broader widthTheta only narrow 10*

Mass “calculated”: Instanton attractions: [ud]~450; (uds*) ~ 750

450

L=1

400 750

Effective mixes [ud]-s* and (uds*)

Theta (1600)

Width

20

Chiral Soliton Theta-N-K Coupling involves threeunknowns A; B; C

B F/DSet scale with g(10*) = 1-B-C

NRCQM: F/D=2/3 B=1/5 no ss* in N: C= 4/5 g(10*)=0

g(10*)

C

After Ellis Karliner Prasalowicz

Width

Width < 10 MeV experiments <1MeV Cahn Trilling; Nussinov;…

Decouples from KN (small width)

Strong coupling to something (strong production) How is Theta produced?

………………enigma

Production

25

Inconsistencies (II)• Production rate (e.g. for Θ+(1540) )

– “Positive” experiments: SAPHIR: RΛ*(1520) ~ 0.3 HERMES: RΛ*(1520) ~ 1.6~3.5 ZEUS: RΛ*(1520) ~ 0.2 ( I estimated from RΛ ~ 0.04 )

SVD-2: RΛ*(1520) > 0.2 ( estimated by SPHINX,

hep-ex/0407026)

– “Negative” experiments: ALEPH: RΛ*(1520) < 0.1 BaBar: RΛ*(1520) < ~ 0.01 Belle: <0.02 HERA-B: RΛ*(1520) < 0.027~0.16 SPHINX: RΛ*(1520) < 0.02

Several experimental limits in hadron production

Some not restrictive yet e.g. psi(3095) to Theta Thetabar (=3080) versus LambdaLambdabar (1/100)or can be “explained away” e.g. hard to make 10 q + q*

My opinion (this week)Limits in high statistics look impressive.Onus is on supporters to explain them away or find a loophole

……….example of a possible loophole Lipkin Karliner next

Why seen in photons but not in high statistics hadrons?

CLAS: Theta+K = N*(2.4GeV) (24ev/10bgnd)

Suppose N*(uddss*) and gamma provides the ss*

Problems

CLAS see in

gammapi

K

Theta

piN

N*

No memory of gamma(ss*); should apply to hadrons too…..why not CDF?

SPring8 and CLAS1 too low E(gamma) to make 2.4GeV N*

The Mystery of the Sigma_5

• The case of the dog that didn’t bark (Sherlock Holmes)

If Theta is real, why isnt Sigma_5

(or Sigma* ½+ 1660) also seen?

Note pKs can be + or +

Decays Dyakanov Petrov Polyakov; Close Dudek; Oh Kim Lee

30

Gamma N \to K ThetaAssuming s,t,u and contact diagrams

Gamma N \to K Sigma5

FC-Q Zhao

Sigma5:Theta photoproduction ratioinsensitive to ENERGY…..

0.5…and to the SigmaPentaquark mixing.

Sigma:Theta> 0.4Could be 0.6

Why not seen in pKs?

FC+Q Zhao

M(pKs)

HERMES

Absence of Sigma_5, or even Sigma(1660)

in experiments that claim Theta is a worry.

(unless Theta (uds*)exists and Sigma (ud*s)doesn’t Vento)

Or Theta and Sigma_5degenerate = extra widthFC Dudek unpublished on grounds of taste

Dzierba Szczepaniak TeigeFake Peaks in gamma N

N

gamma

N

a2/rho3

35

Dzierba Szczepaniak Teige

Fake Peaks in gamma N

N a2/rho3

NK K-

+

D/F wave decay forward backto KKbar

a2/rho3 gives charge asymmetry

Narrow K+nBroad K-n

Same velocity NK mass 1440“real” kinematics broadens hump….

Dzierba Szczepaniak Teige

One is real (CLAS)Three are fake

Can you tell which?

(LEPS)

nK

Could this also explain different nK+ and pKs masses?

0SpK

F. Close and Q. Zhao, hep-ph/0404075

Show Dalitz plots!!

Different Q valuesfor charged neutralfeed into mass offake Theta?

Exotic Mesons inspired by pentaquark correlations

39

--

L=1……making exotic 1-+ mesons……et al

++

--++ + -

-+

+/-

Burns Close Dudek based on KL

L

L L

Exotic Pentaquarks Exotic Mesonsgeneral problem with clustered quark models, for example triquark - diquark:

Kochelev, Lee & Vento

S=+2 meson =

suppresses decay width

narrow, strangeness +2 meson near 1600 MeV

apply same logic to

• Three overheads on 1-+ pi_1(1400) and pi_1(1600) as correlated

q*(qqq*) \pm q(q*q*q)

Burns Close Dudek

Paradoxes; Enigmas; Hints of unreality

How is Theta produced?Why seen in low statistics photoproduction but not in high statistics hadroproduction?

Decouples from KN (small width)Strong coupling to something (strong production)

Why does mass vary?real (dynamic clue); statistics (non existence clue)

Cascades (exotics) studied since BQM Beware!

K-Theta+ why no K+Sigma-Ks Theta+ why no Ks Sigma+

Why is productionTheta/Sigma(1660)= infinity?

CONCLUSION

Have Weird Multiquark Demons been found?

Is there a 1 MeV wide, S=+1 baryon at 1540 MeV?

If NO this is testament to the ingenuity of theorists whosemodels can explain it even if it doesn’t exist.

Lattice QCD is almost unique in not havingdefinitively disproved that such a state does not exist.

CONCLUSION

• YES

• No

• Keep searching

Have Weird Multiquark Demonsbeen found?

Democratic voting paper/Florida counting principle

This slide sponsored by Oxford University Press

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D K-pK+n 3-body Dalitz plot

10bar and hidden octet: threats and opportunities

Also exotic Xi^o Xi^- BecauseI=3/2Multiplet !

Exotic cornersTheta+ Xi+ Xi - -With non-exoticOctet as well

ud udQ*

udQ* (ud) S=1;col=6 attractive Karliner Lipkin

(ud) S=0;col=3* attractive; mix; lowers energyHogaasen Sorba

Quasi Two Body Hadrons

e.g. Karliner Lipkin

Overlap with color 1 uQ* or dQ* = instability Hogaasen Sorba

u d u d

Q*

u d

Jaffe Wilczek

ud udQ*

Karliner Lipkin

Q* \to (ud) = anomalous deuteron

(ud) \to Q* 10bar mesons

P-wave 1-+ etc? e.g.Chung KlemptWidths? FC Burns

Forces ud very light and L largeWhat mechanism?

What if……..?

38

+ +

- -

Scalar diquarks……making Scalar mesons

meson

Jaffe 77; Maiani et al 04

Width < 10 MeV direct experiments <1MeV Cahn Trilling; Nussinov;…

3/2- Lambda(1520) KN width 7 MeV

Jaffe Wilzcek; Jennings Maltman; Carlson et al; Close Dudek;Buccella Stora

Color flavor spin overlap suppression > 24

X D wave; P-wave Lambda1600 is 100 MeVX needs qq* creation whereas qqqqq* falls apart

X color killed by soft gluon exchangeX spin flip costs littleX flavor killed by rearrangement

CLAS - +(1540) and N* ?

proton

+N* K+

n

K-