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The Hadron Spectrum and QCD. Curtis A. Meyer Carnegie Mellon University 03 December 2007. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A A A. The beginning of time. The Hadron Spectrum and QCD. The strong force - PowerPoint PPT Presentation
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December 3, 2007UTK Colloquium1
The Hadron Spectrum and
QCD
Curtis A. MeyerCarnegie Mellon University 03 December 2007
December 3, 2007UTK Colloquium2
The beginning of time.
The strong force and QCD
Color confinement
BaryonSpectroscopy
Finding Gluonic Hadrons
Confinement
The Hadron Spectrum and
QCD
Curtis A. MeyerCarnegie Mellon University 03 December 2007
December 3, 2007UTK Colloquium3
The First Seconds
of The Universe
December 3, 2007UTK Colloquium4
Quark Gluon Plasma
For a period from about 10-12 s to 10-6 s the universecontained a plasma of quarks, anti quarks and gluons.
Relativistic Heavy Ion Collisions are trying to produce this state of matter in collisions
December 3, 2007UTK Colloquium5
Confinement
From about 10-6 s on, the quark and anti quarks became confined inside of Hadronic matter. At the age of 1s, only protons and neutrons remained.
BaryonsMesons
Flux
tube
forms
between
qqThe gluons producethe 16ton force thatholds the hadronstogether.
December 3, 2007UTK Colloquium6
The Formation of Nuclei
By the old age of three minutes, the formation of low mass nuclei was essentially complete.
Primordial hydrogen, deuterium, helium and afew other light nuclei now exist.
It will be nearly a half a million years beforeneutral atoms will dominate matter.
December 3, 2007UTK Colloquium7
Quantum Chromo
The rules that govern how the quarks froze out into hadrons are given by QCD.
Three charges called RED, BLUE andGREEN, and three anti colors. The objects that form have to be colorneutral:
Just like atoms areelectrically neutral,hadrons have to beneutral.
Color Charge
Dynamics
December 3, 2007UTK Colloquium8
Gluons Carry the Force
G R
RG
G R
Meson Meson
Time
The exchange of gluons is continually changing theIndividual colors of the quarks, but the overallColor remains neutral
R R
G
G
BB
December 3, 2007UTK Colloquium9
Gluons Carry the Force
G R
RG
G R
Meson Meson
Time
The exchange of gluons is continually changing theIndividual colors of the quarks, but the overallColor remains neutral
R R
G
G
BB
December 3, 2007UTK Colloquium10
Gluons Carry the Force
G R
RG
G R
Meson Meson
Time
The exchange of gluons is continually changing theIndividual colors of the quarks, but the overallColor remains neutral
R R
G
G
BB
Gluons produce the forces thatconfine the quarks, but the gluonsdo not appear to be needed tounderstand normal hadrons
December 3, 2007UTK Colloquium11
Flux TubesFlux
tube
forms
between
Color Field: Because of self interaction, confining flux tubes form between static color charges Confinement arises
from flux tubes and their excitation leads to a new spectrum of mesons
December 3, 2007UTK Colloquium12
Flux Tubes
December 3, 2007UTK Colloquium13
• quarks can never be isolated• linearly rising potential
– separation of quark from antiquark takes an infinite amount of energy
– gluon flux breaks, new quark-antiquark pair produced
Quark Confinement
December 3, 2007UTK Colloquium14
Observed Hadrons
In nature, QCD appears to have two configurations. three quarks (qqq) Baryons proton: uud neutron: udd quark-antiquark (qq) Mesons pion: ud , 1p
2
¡uu ¡ dd
¢, du
There are a large number of excited states which arealso considered particles. QCD should predict thesespectra and we can compare them to experiment.
Color singlet objects observed in nature:
Allowed systems: , , ggggg, gqq qqqqqqqg
Beyond these simple systems, others are allowed
December 3, 2007UTK Colloquium15
The BaryonsWhat are the fundamental degrees of freedominside of a proton and a neutron? Quarks? Combinations of Quarks? Gluons?The spectrum is very sparse.
The MesonsWhat is the role of glue in a quark-antiquarksystem and how is this related to the confinementof QCD?What are the properties of predicted states beyond simple quark-antiquark? qqg , Need to map out new states.
December 3, 2007UTK Colloquium16
The Baryon SpectrumMeasured in the reaction ¼ N ! ¼ N. Workdone in 60’s to early 90’s.
December 3, 2007UTK Colloquium17
The Baryon Spectrum
In the quark model picture,allow individual quarks tobe excited to higher levels:baryon: q(1s)q(1s)q(1s)
1s -> 2s, 1s -> 2p
NucleonL2I,2J (Mass) Parity Status
P11(938) + ****S11(1535) - ****S11(1650) - ****D13(1520) - ****D13(1700) - ***D15(1675) - ****
P11(1440) + ****P11(1710) + *** P11(1880) + P11(1975) +P13(1720) + ****P13(1870) + *P13(1910) +P13(1950) +P13(2030) +F15(1680) + ****F15(2000) + **F15(1995) +F17(1990) + **
****, *** Known **,* Hints
December 3, 2007UTK Colloquium18
NucleonL2I,2J (Mass) Parity Status
P11(938) + ****S11(1535) - ****S11(1650) - ****D13(1520) - ****D13(1700) - ***D15(1675) - ****
P11(1440) + ****P11(1710) + *** P11(1880) + P11(1975) +P13(1720) + ****P13(1870) + *P13(1910) +P13(1950) +P13(2030) +F15(1680) + ****F15(2000) + **F15(1995) +F17(1990) + **
Missing Baryons
The Baryon Spectrum
****, *** Known **,* Hints
In the quark model picture,allow individual quarks tobe excited to higher levels:baryon: q(1s)q(1s)q(1s)
1s -> 2s, 1s -> 2p
December 3, 2007UTK Colloquium19
Treat a quarks and a diquarkas the fundamental particles.Allow excitations as before:
NucleonL2I,2J (Mass) Parity Status
P11(938) + ****S11(1535) - ****S11(1650) - ****D13(1520) - ****D13(1700) - ***D15(1675) - ****
P11(1440) + ****P11(1710) + *** P11(1880) + P11(1975) +P13(1720) + ****P13(1870) + *P13(1910) +P13(1950) +P13(2030) +F15(1680) + ****F15(2000) + **F15(1995) +F17(1990) + **
The Baryon Spectrum
****, *** Known **,* Hints
December 3, 2007UTK Colloquium20
Looking in the wrong place
Nearly all the data used to identify baryons has comefrom ¼ N scattering.
¼ N ! ¼ N
What if the missing statesdo not couple to ¼ N ?
(1/2)-
(1/2)-
(3/2)-
(3/2)-
(5/2)-
(1/2)+
(1/2)+
(1/2)+
(1/2)+
(3/2)+
(3/2)+
(3/2)+
(3/2)+
(3/2)+
(5/2)+
(5/2)+
(5/2)+
(7/2)+
Quark model predictions thatmany of the missing stateshave strong couplings to other final states: N´ N! …
December 3, 2007UTK Colloquium21
Lattice CalculationsFirst lattice calculation for baryons (2006). Manyapproximations, but shows what will be possible.
December 3, 2007UTK Colloquium22
Incident electron and tagged photon beams (both polarized and unpolarized) (<6GeV) Targets (H, D, 3He … ) (both polarized and unpolarized)
Large acceptance detector with access to final states with several particles and PID
Large data sets bothcurrently in hand as well as new ones expected in the next few years
Identify Baryons:N*, , , ,
The CLAS Detector at JLab
December 3, 2007UTK Colloquium23
Using 11TB of CLAS data from a recent run period, simultaneously analyzing reactions:
p ! p p ! p ’
p ! p p ! K+
P ! 0K+
p ! p+-
700,000 Events 250,000 Events8,000,000 Events1,200,000 Events1,100,000 Events¼ 1 Events
None of these channels have been extensively studied, but are supposed to couple to some missing baryons.Significant New Data
New Data Sets
Enormous data sets requirenew tools to carry out theneeded analysis.
December 3, 2007UTK Colloquium24
Partial Wave Analysis
Angular distributions of reactions let you determinethe spin and parity of intermediate resonances.
Classical Electrodynamics:
Monopole Radiation (L=0)
Dipole Radiation (L=1)
Quadrupole Radiation (L=2)
December 3, 2007UTK Colloquium25
Partial Wave AnalysisFor a given reaction energy, quantum mechanical amplitudes yields a probability distribution and predicts angular distributions.
Particles nominally occur as a resonance which hasboth an amplitude and phase as a function of thedifference between its nominal mass and the reaction energy.
Fit the angular distribution as a sum of complex amplitudes which describe particular quantum numbers.
December 3, 2007UTK Colloquium26
Partial Wave Analysis
A simple model with threecomplex amplitudes, 2 ofwhich are particles withdifferent QNs
Start with a single energybin.
Fit to get the strengths andthe phase difference betweenthe two resonances.
December 3, 2007UTK Colloquium27
Partial Wave Analysis
A simple model with threecomplex amplitudes, 2 ofwhich are particles withdifferent QNs
Start with a single energybin.
Fit to get the strengths andthe phase difference betweenthe two resonances.
Fit a 2nd bin.
December 3, 2007UTK Colloquium28
Partial Wave Analysis
A simple model with threecomplex amplitudes, 2 ofwhich are particles withdifferent QNs
Start with a single energybin.
Fit to get the strengths andthe phase difference betweenthe two resonances.
Continue fitting bins …
December 3, 2007UTK Colloquium29
Partial Wave Analysis
A simple model with threecomplex amplitudes, 2 ofwhich are particles withdifferent QNs
Start with a single energybin.
Fit to get the strengths andthe phase difference betweenthe two resonances.
… and continue …
December 3, 2007UTK Colloquium30
Partial Wave Analysis
A simple model with threecomplex amplitudes, 2 ofwhich are particles withdifferent QNs. The massespeak where the two linesare.
The need for intensity and the phase difference areindicative of two resonances.
Can fit for masses and widths.
December 3, 2007UTK Colloquium31
° p ! ! pAny analysis needs to incorporate many differentprocesses. However, all the analyses of differentchannels need to be self consistent (E.g. couplingconstants, production and decay … ).
Tools developed at CMU over the last 3 years allow the easy input of any amplitude directly at the event level in the analysis
Theory Experiment
Partial Wave Analysis
I = § | almn Almn | 2 Complex amplitudes andcomplex fit parameters.
The ! p system has never been studied
About 13 million events in ~100 narrow energy bins
First time this type of PWA has been done for Baryons
December 3, 2007UTK Colloquium32
PWA ResultsFit showing three amplitudes.
(3/2)- D13
(5/2)+ F15
t-channel
Intensities
Phase DifferenceStrong evidence for:
(3/2)- N(1700) ***(5/2)+ N(1680) ****(7/2)- N(2190) ****
° p ! ! p
Not Expected
The strong signals are well known states!
December 3, 2007UTK Colloquium33
Comparison to Modelst-channel is from models fit to earlier data
December 3, 2007UTK Colloquium34
Comparison to Modelst-channel is from models fit to earlier data
Improvement following recent predictions by Barnes.
December 3, 2007UTK Colloquium35
(1/2)-
(1/2)-
(3/2)-
(3/2)-
(5/2)-
(1/2)+
(1/2)+
(1/2)+
(1/2)+
(3/2)+
(3/2)+
(3/2)+
(3/2)+
(3/2)+
(5/2)+
(5/2)+
(5/2)+
(7/2)+
What is seen?
Strong evidence for:
(3/2)- N(1700) ***(5/2)+ N(1680) ****(7/2)- N(2190) ****
(7/2)- G17(2190) ****
Hints?
December 3, 2007UTK Colloquium36
Baryon AnalysisThe data demand need three baryon resonances. (3/2)- , (5/2)+ and (7/2)-
These are not “missing states”.
There may be some hints of missing baryons in the data, but the models for the non-resonant partsneed to be improved (theoretical input).
We also have a number of other analysis efforts underway looking at other final states and anticipatemore definitive statements in the next year or so.
December 3, 2007UTK Colloquium37
Mesons: quark-antiquark systems
What is the role of glue in a quark-antiquarksystem and how is this related to the confinementof QCD?
What are the properties of predicted states beyond simple quark-antiquark? qqg , Need to map out new states.
December 3, 2007UTK Colloquium38
Positronium
e+ e-
Spin: S=S1+S2=(0,1)
Orbital Angular Momentum: L=0,1,2,…
Reflection in a mirror: Parity: P=-(-1)(L)
Total Spin: J=L+S L=0, S=0 : J=0 L=0, S=1 : J=1L=1 , S=0 : J=1 L=1, S=1 : J=0,1,2
… …
Particle<->Antiparticle: Charge Conjugation: C=(-1)(L+S)
Notation: J(PC) 0-+, 1--, 1+-, 0++, 1++, 2++ (2S+1)LJ
1S0, 3S1, 1P1, 3P0, 3P1, 3P2,…
SpectroscopyA probe of QED
December 3, 2007UTK Colloquium39
Quarkonium
q q
0-+
1+-
1--
0++1++2++
2-+1--2--3--
4++
2++3++
3+-
S=1S=0L=0
L=1
L=2
L=3
Mesons
Consider the three lightest quarks
sdu ,,sdu ,, 9 Combinations
dduu 2
1
ssdduu 3
1 ssdduu 26
1
duud
susd
usds
radi
al
Spectroscopy and QCD
December 3, 2007UTK Colloquium40
Quarkonium
q q
0-+
1+-
1--
0++1++2++
2-+1--2--3--
4++
2++3++
3+-
S=1S=0L=0
L=1
L=2
L=3
Mesons
,K,,’
,K*,,
b,K,h,h’
a,K,f,f’
,K,,’
,K*,, Mesons come in Nonets of the sameJPC Quantum Numbers
SU(3) is brokenLast two members mix
Spectroscopy an QCD
December 3, 2007UTK Colloquium41
Quarkonium
q q
0-+
1+-
1--
0++1++2++
2-+1--2--3--
4++
2++3++
3+-
S=1S=0L=0
L=1
L=2
L=3
Mesons
Quarkonium
Allowed JPC Quantum numbers:
0++ 0-+
1–- 1++ 1+-
2-- 2++ 2-+
3-- 3++ 3+-
4-- 4++ 4-+
5-- 5++ 5+-
0-- 0+-
1-+
2+-
3-+
4+-
5-+
Exotic Quantum Numbersnon quark-antiquark description
Spectroscopy an QCD
Nothing to dowith Glue!
December 3, 2007UTK Colloquium42
QCD Potential
linear potential
ground-state flux-tube m=0
excited flux-tube m=1
Gluonic Excitations provide anexperimental measurement of the excited QCD potential.
Observations of the nonets on the excited potentials are the best experimental signal of gluonic excitations.
December 3, 2007UTK Colloquium43
Hybrid Meson Predictions
Flux-tube model: 8 degenerate nonets 1++,1-- 0-+,0+-,1-+,1+-,2-+,2+- ~1.9 GeV/c2
S=0
1.0
1.5
2.0
2.5
qq Mesons
L = 01 2 3 4
exoticnonets
0 – +0 + –1 + +1 + –1– +1 – –2 – +2 + –
Hybrids
S=1
Start with S=01++ & 1--
Start with S=10-+ & 0+-
1-+ & 1+-
2-+ & 2+-
qqg
December 3, 2007UTK Colloquium44
Flux-tube model: 8 degenerate nonets 1++,1-- 0-+,0+-,1-+,1+-,2-+,2+- ~1.9 GeV/c2
Lattice calculations --- 1-+ nonet is the lightest UKQCD (97) 1.87 0.20MILC (97) 1.97 0.30MILC (99) 2.11 0.10Lacock(99) 1.90 0.20Mei(02) 2.01 0.10Bernard(04) 1.792§0.139In the charmonium sector:1-+ 4.39 0.080+- 4.61 0.11
Splitting = 0.20
1-+ 1.9+/- 0.22+- 2.0+/- 0.110+- 2.3+/- 0.6
S=0 S=1
Hybrid Predictions
December 3, 2007UTK Colloquium45
Looking for Hybrids
Meso
n
Meso
nM
eson
Decay Predictions
Lglue
Angular momentumin the gluon flux stays confined.
This leads to complicated multi-particle final states.
Analysis MethodPartial Wave Analysis
Fit n-D angular distributionsFit Models of production and decay of resonances.
1 IG(JPC)=1-(1-+)
’1 IG(JPC)=0+(1-+)
1 IG(JPC)=0+(1-+)
K1 IG(JPC)= ½ (1-)Nine state
December 3, 2007UTK Colloquium46
Experimental Evidence
New York Times, Sept. 2, 1997
Hybrids
Exotic Mesons1-+ mass 1.4E852 BNL ’97CBAR CERN ’97
Too lightNot Consistent Possible rescattering (?)Decays are wrong (?)
Not a Hybrid
December 3, 2007UTK Colloquium47
p p
At 18 GeV/c
suggests p 0 p
p
to partial wave analysis
M( ) GeV / c2 M( ) GeV / c2
E852 Results
December 3, 2007UTK Colloquium48
An Exotic Signal
LeakageFrom
Non-exotic Wavedue to imperfectly
understood acceptance
ExoticSignal
1
Correlation ofPhase
&Intensity
M( ) GeV / c2
1(1600)
3 m=1593+-8+28-47 =168+-20+150
-12
’ m=1597+-10+45-10 =340+-40+-50
December 3, 2007UTK Colloquium49
-p +--p
1(1600) f1
E852 Results
-p 0-p 1(1600) b1
Mass = 1.6870.011 GeV
Width = 0.2060.03 GeV
Mass=1.7090.024 GeV
Width=0.4030.08 GeV
In both b1 and f1, observeExcess intensity at about2GeV/c2.Mass ~ 2.00 GeV, Width ~ 0.2 to 0.3 GeV
In Other Channels1-+ in f1 and b1
December 3, 2007UTK Colloquium50
New Analysis
Dzierba et. al. PRD 73 (2006)
Add 2(1670) ! (L=3)Add 2(1670) ! 3Add 2(1670) ! ()SAdd a3 decaysAdd a4(2040)
10 times statistics ineach of two channels.
Get a better descriptionof the data via momentscomparison
No Evidence for the 1(1670)
December 3, 2007UTK Colloquium51
1(1400) Width ~ 0.3 GeV, Decays: only weak signal in p production (scattering??) strong signal in antiproton-deuterium.
1(1600) Width ~ 0.16 GeV, Decays ,’,(b1) Only seen in p production, (E852 + VES)
1(2000) Weak evidence in preferred hybrid modes f1 and b1
NOT AHYBRID
Doesthis exist?
The rightplace. Needsconfirmation.
Exotic Signals
These are all the same member of a nonet.
December 3, 2007UTK Colloquium52
Experimental Evidence
New York Times, Sept. 2, 1997Hybrid
Nonets
dduu 2
1
ssdduu 3
1 ssdduu 26
1
duud
susd
usds
Built on normal mesons
Identify otherstates in nonetto establish hybrid
Establish other Nonets: 0+- 1-+ 2+-
1-+
Levels
December 3, 2007UTK Colloquium53
Jefferson Lab Upgrade
December 3, 2007UTK Colloquium54
CHL-2CHL-2
Upgrade magnets Upgrade magnets and power and power suppliessupplies
Jefferson Lab Upgrade
320M$ DOE finished in 2014 (I started in 1997)
December 3, 2007UTK Colloquium55
The GlueX Experiment New Facility
December 3, 2007UTK Colloquium56
Beams of photons may be a more naturalway to create hybrid mesons.
Simple QN counting leads to the exotic mesons
There is almost no data for photon beams at9GeV energies. GlueX will increase data by
3-4 orders of magnitude.
How to Produce Hybrids
December 3, 2007UTK Colloquium57
Coherent
flu
x
photon energy (GeV)
12 GeV electrons
This technique provides requisite energy, flux and
polarization
collimated
Incoherent &coherent spectrum
tagged
with 0.1% resolution
40%polarization
in peak
electrons in
Linearly polarizedphotons out
spectrometer
diamondcrystal
Bremsstrahlung
December 3, 2007UTK Colloquium58
ExoticsExotics
N N
e
X
,,
1 IG(JPC)=1-(1-+)
’1 IG(JPC)=0+(1-+)
1 IG(JPC)=0+(1-+)
K1 IG(JPC)= ½ (1-)
1-+ nonet
Need to establish nonet nature of exotics: 0
Need to establish more than onenonet: 0+- 1-+ 2+-
In Photoproduction
Need very good partial wave analysis.
Current DOE plan GlueX starts in 2014
December 3, 2007UTK Colloquium59
Gluonic Hadrons and Confinement
Non-gluonic mesons – ground state glue.
Potentials correspondingTo excited states of glue.
Lattice QCD potentials
What are the light quarkPotentials doing?
E
December 3, 2007UTK Colloquium60
Conclusions
The quest to understand confinement and the strong force is about to make great leaps forward.
Advances in theory and computing will soon allow us to solve QCD and understand the baryon spectrum and the role of glue.
The definitive experiments toconfirm or refute our expectationson the role of glue are being built.
The synchronized advances in both areas will allowus to finally understand QCD and confinement.
New results on baryons and theoretical work on models is near to giving us newinsight on the observed baryons.
December 3, 2007UTK Colloquium61
December 3, 2007UTK Colloquium62
-p ’-p at 18 GeV/c
The 1(1600) is the Dominant signal in ’.Mass = 1.5970.010 GeVWidth = 0.3400.040 GeV 1(1600) ’
E852 Results
In Other Channels
1-+ in ’