LHP ‘06 - GlueX & Lattice QCD - J. Dudek
The GlueX Experiment and Lattice QCD
Jo Dudek, Jefferson LabLHP ‘06
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
The Physics of GlueX
! GlueX will explore the meson spectrum with a mass reach over 2.5 GeV
! major feature is the search for exotic quantum-numbered mesons
! e.g. not accessible to a fermion-antifermion state
! likely origin for such states in QCD is hybrid mesons - i.e. quark-antiquark states with excited gluonic field
0!!
, 0+!
, 1!+
, 2+!
. . .JPC
=
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
The GlueX Experiment
! GlueX will use real 9 GeV photons to photoproduce mesons
! virtually no data on photoproduction of meson resonances exists
SLAC bubble chamber
19 GeV photons (1991)40 evts
3 2.4
CLAS
5.5 GeV photons (2005)
m(!!!) / GeV
4000 evts
m(!!!) / GeV1
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
GlueX Details
! GlueX will hugely surpass these statistics
! 106 !!! events per 10 MeV bin in 3 months running
! ~ 1 PetaByte per year
! detector designed to have good coverage over full 4!
! aids the required Partial Wave Analysis
0
5000
10000
15000
20000
25000
30000
35000
40000
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
500
1000
1500
2000
2500
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
10000
20000
30000
40000
50000
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
5000
10000
15000
20000
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
1
2
3
4
5
6
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
1
2
3
4
5
6
1 1.2 1.4 1.6 1.8 2 2.2 2.4
0
1
2
3
4
5
6
1 1.2 1.4 1.6 1.8 2 2.2 2.4{1++ 0+ "!s2++ 1+ "!D 2-+ 0+ f2!s0-+ 0+ f0!s
!X ! !2++
reducing model dependence actively researched
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
GlueX Photon Beam & Detector
this guy trying to work
out who stole the other
half of the detector
acceptance estimates
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Exotics in Experiment
! bulk of relevant exotic searches done by E852 using a 18 GeV pion beam & dominantly
! !p ! !"N
!!
"
2++
1!+
60016,000
2++
1!+
3,000
1,000
!0"
a2
a2
1!+
1.0 1.4 1.8 1.0 1.4 1.8
!1(1400), #~400 MeV or non-
resonant interaction ?no clear sign of a resonance in the P-wave intensity
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Exotics in E852
!p ! !!
""p
a2
?
1!+
2++
broad enhancement in
P-wave intensity
D-wave structure not
understood so phase
comparison unconstrained
taken at face value,
intensity gives
!1(1600), #~350 MeV
non-resonant origin
cannot be ruled out
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Exotics in E852
! two analyses of , more recent has higher statistics
!p ! !!!p
1500
E852 (2001) grey points use a more truncated wave-set lacking some
waves2!+
claimed explanation of difference is !2(1670)
missing waves being assigned to exotic wave by PWA
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
E852 Exotics cont...
!p ! !!!!!p
1!+(b1!)S
2++(!")S
4++(!")D
1!+(b1!)S
phase
exotic enhancement in the 1.65 GeV region
low event statistics limit the PWA to a small
number of waves
1!+
! 2++
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
E852 Exotics cont...
!p ! "!!!p
1++(f1!)P
2!+(f1!)D
1!+(f1!)S
exotic enhancement in
the 1.7 GeV region
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Exotics in Experiment
! E852 results suggestive, but situation unclear overall
! GlueX poised to continue the good work of hybrid-hunting with a new production mechanism and much greater statistics
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Models of Gluonic Excitations
! the flux-tube model has historically dominated the field
! has a rather complete phenomenological coverage
! mass spectrum estimates (Isgur & Paton)
! hadronic decay widths (Isgur, Kokoski, Close, Page ...)
! photocouplings (Close & JJD)
!m !
!
1
r
"
⇒ “S+P” rule
AH
AC
!"
b
mq
! O(1)
mH ! 2 GeV
1!+
, 0+!
, 2+! + non-exotics
!1 $ ! b1
!1 $ ! "~
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lightest 1-+ from Lattice QCD
! summary of world simulation data
0 0.5 1 1.5m! / GeV
0
1
2
3
m!
1 / G
eV
m !m ss
quenched
NF=2, NF=3
NF=2+1
mostly old studies w/
coarse lattice spacings
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lightest 1-+ from Lattice QCD
! JLab effort over next two years aim to significantly improve this picture
two lattice spacings, as = 0.10, 0.125 fm
two volumes V = 2.4, 3.2 fm 1/at = 6 GeV
0 0.5 1 1.5m! / GeV
0
1
2
3
m!
1 / G
eV
m !m ss
dynamical (NF=2+1)
anisotropic Clover
dynamical
& partially quenched points
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Wider Meson Spectrum
! GlueX will be a meson spectrometer of broad scope
! JLab lattice QCD spectrum program has same aim
! excited states in a given JPC via variational method
! large set of JPC using big operator basis
e.g. baryon sector
work by LHPC claims
9 excited states !
!!!
Dµ ! !!!
Dµ
!
D! !!!! !!Fµ!!+ two-meson style operators
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Photocouplings
! GlueX will photoproduce mesons
! couplings virtually unknown even for conventional mesons - clear target for Lattice QCD predictions
!
p N
resonance, X
‘exchange’
meson, M
!!M |X"photocoupling
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lattice Method
! three-point functions with vector current
!(tf , t ; !pf , !q) =!
!x,!y
e!i!pf ·!xei!q·!y !"f (!x, tf )jµ(!y, t)"i(!0, 0)"
!!
n,m
e!Efn (tf!t)"0|!f (0)|fn("pf )#
!"fn(!pf )|jµ(0)|im(!pi)#
!"im(!pi)|"i(0)|0#e!Eint
transition
matrix element
covariant transition
matrix element to be
extracted
energies and overlap
factors extracted from
fits to two-point functions three-point function
calculation performed via a
sequential-sink construction
smeared interpolators!!!
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Charmonium
! before calculating with light quarks for GlueX we’d like to test the technology
! charmonium is ideal
! excellent exptal data
! near-stable states
! quenched might be‘tolerable’
quenched aniso. %=3
1/at ~ 6 GeV
DWF (mcat ~ 0.15)
300 cfgs.
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
! transverse E1(Q2) and longitudinal C1(Q2)!S(!pS)|jµ(0)|V (!pV , r)" =
!!1(Q2)
!
E1(Q2)
"
!(Q2)"µ(!pV , r) # "(!pV , r).pS
#
pµV pV .pS # m2
V pµS
$
%
+C1(Q2)&
q2mV "(!pV , r).pS
"
pV .pS(pV + pS)µ # m2
SpµV # m2
V pµS
%
'
.
not used
in the fit
E1(Q2) = E1(0)
!
1 + Q2
!2
"
e!
Q2
16"2
PDG
CLEO
lat.
!c0 ! J/"#
!S(!pS)|jµ(0)|V (!pV , r)" =
E1(Q2)
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
! transverse E1(Q2), M2(Q2) and longitudinal C1(Q2) !A(!pA, rA)|jµ(0)|V (!pV , rV )" = i
4!
2!(Q2)"µ!"#(pA # pV )#$
$
!
E1(Q2)(pA + pV )"
"
2mA[""( !pA, rA).pV ]"!( !pV , rV ) + 2mV ["(!pV , rV ).pA]""!(!pA, rA)#
+ M2(Q2)(pA + pV )"
"
2mA[""( !pA, rA).pV ]"!( !pV , rV ) # 2mV ["(!pV , rV ).pA]""!(!pA, rA)#
+C1(Q2)
$
q2
"
# 4!(Q2)""!(!pA, rA)""(!pV , rV )
+ (pA + pV )"
%
(m2A # m2
V + q2)[""(!pA, rA).pV ] "!(!pV , rV ) + (m2A # m2
V # q2)["(!pV , rV ).pA] ""!( !pA, rA)&#
'
.
0 1 2 3 4 5 6
Q2 (GeV
2)
-0.25
-0.2
-0.15
-0.1
-0.05
0
a tM
2(Q2 )
spat. pf = (000) !c1 snk.
spat. pf = (100) !c1 snk.
0 1 2 3 4 5 6
Q2 (GeV
2)
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
a tE
1(Q2 )
spat. pf = (000) !c1 snk.
spat. pf = (100) !c1 snk.
PDG phys. massPDG lat. massCLEO phys. massCLEO lat. mass
!c1 ! J/"#
E1(Q2) M2(Q2)
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Summary
! GlueX is a major component of the JLab 12 GeV upgrade
! will exceed total world meson production data in a few years
! search for exotic mesons a main focus
! JLab lattice QCD program aligned with GlueX aims
! dynamical 2+1 anisotropic Clover lattices to be used for spectrum, decay and photocoupling studies at low pion masses
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Hadronic Decays
! some recent lattice progress on this important topic
! Lüscher method study : Cook & Fiebig
! use volume dependence where m(!) + m(b1) < m(!1) or m(!) + m(a1) < m(&1)
quenched 103x24 & 123x24 with Wilson quarks
m(!) ~ 1800 MeV
very large extrapolation
to level crossing
0 0.5 1 1.5m! / GeV
0
1
2
3
m!
1 / G
eV
m !m ss
~ m b 1 + m !
~ m " + 2 m !
*
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
CLAS PWA
16,000
80,000
16,000
exotic maybe 1-2% of 1++ in pion prod, appears to be about 20% here
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Hadronic Decays cont.
! some recent lattice progress on this important topic
! alternative approach due to Michael & McNeile
! tune quark masses to m(!) + m(b1) " m(!1)
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lightest 0+- from Lattice QCD
! summary of world simulation data
quenched
0 0.5 1 1.5m! / GeV
0
1
2
3
mb 0 /
GeV
m !m ss
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lightest 2+- from Lattice QCD
! summary of world simulation data
quenched
0 0.5 1 1.5m! / GeV
0
1
2
3
mb 2 /
GeV
m !m ss
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Lattice QCD & model testing
! quark masses will decrease in the future, but even now we can make good use of lattice data
! we can compare lattice QCD calculations with ‘heavier’ quarks vs model calculations with ‘heavier’ quarks
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
Exotics in E852
! two analyses of , more recent has higher statistics
!p ! !!!p
1500
40,0002++(!")D1+
E852 (2001) grey points use a more truncated waveset lacking some
waves2!+
claimed explanation of difference is !2(1670)
leaking into exotic wave
LHP ‘06 - GlueX & Lattice QCD - J. Dudek
0 2 4 6 8 10 12 14 16 18 20 22 24t
0.67
0.68
0.69
0.7
0.71
0.72
0.73
0.74
0.75
0.76
mef
f
g.s.
1st ex?
meff
Variational Method
! traditional method
! variational method e.g. baryon sector
work by LHPC
9 excited states !
g.s.
1st ex
2nd ex
3rd ex4th ex