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XXI Physics in Collision Conference Seoul Korea June 28 - 30 2001. High Q 2 Physics. Christopher M. Cormack Rutherford Appleton Laboratory. Contents. - PowerPoint PPT Presentation
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XXI Physics in Collision Conference
Seoul
Korea
June 28 - 30 2001
Christopher M. Cormack
Rutherford Appleton Laboratory
High QHigh Q22 Physics Physics
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 2/35
ContentsContents
• Introduction• HERA• DATA • H1 / ZEUS Detectors
• Neutral Current• Z Exchange
• Charged Current• W Exchange
• New Physics ?• LQ Resonances• Isolated Leptons• Top Searches
• The Future
• Summary + Outlook
A very broad range of subjects for High Q2 and High PT
- Results include Structure Functions from H1 + ZEUS Exotics Phenomena - overlap with HERA, LEP,
TEVATRON
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 3/35
The Electron-Proton Collider
1994-1997
1998-2000
e+p and e-p
IntroductionIntroduction
Luminosity (pb-1)H1 ZEUS
e-P16 16
e+P100 110
Luminosity Delivered
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 4/35
HERA Deep Inelastic Scattering KinematicsHERA Deep Inelastic Scattering Kinematics
Kinematic Variables
222 )( kkqQ Resolving power
Negative of the four-momentum transfer between lepton and proton
“Momentum fraction of proton carried by the struck quark” qp
Qx
2
2
kp
qpy
Inelasticity
Momentum fraction of the lepton carried by the exchange
22 )( qpW 2)( kps sxM
0,, Z
e+/-
kk
x
,Q2q
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 5/35
HERA KINEMATIC PLANEHERA KINEMATIC PLANE
• Accessible Kinematic Plane now almost completely covered
• Measurements extend to cover high y, high x and very high Q2
• Probe distances to ~ 1/1000th of proton size
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 6/35
H1 Detector at HERAH1 Detector at HERA
NC
e+/- p
Fine Grained Liquid Argon Calorimeter (45 000 channels)
EM section %1%12
EE
E
HAD section %1%50
EE
E
Tracking Chambers
ppp 003.0/
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 7/35
ZEUS Detector at HERAZEUS Detector at HERA
Compensating Uranium-Scintillator Calorimeter
EM section EE
E %18
HAD section EE
E %35
Tracking Chambers
TTTT pppp /0014.00065.00058.0/
CC
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 8/35
NCL
2NC3
NC24
2
2
eNC
2 2FyxFYFY
xQdxdQ
d P
L.O. QCD:
Neutral Current DIS Structure FunctionsNeutral Current DIS Structure Functions
Reduced cross section
NCL
NCNCNC
NC FY
yxF
Y
YF
dxdQ
d
Y
xQ
2
322
2
2
4 1
2~
22
2
22 cossin4
1
ZWWZ MQ
Q
Quarks
fNC QxqQxqQAxF )],(),()[( 222
2
Quarks
fNC QxqQxqQBxxF )],(),()[( 222
3
Photon, Z couples to all quark flavours
Parity Violating term - sensitivity to valence quarks
Z exchange
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 9/35
• Standard Model shows good agreement over 6 orders of magnitude
• Effect of the Z0 contribution fron xF3 clearly seen at high Q2
Neutral Current DIS -Neutral Current DIS - 2/ dQd
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 10/35
Neutral Current DIS - Effect of ZNeutral Current DIS - Effect of Z00 Exchange Exchange
22 GeV 000 10 Q dx
d
• e - p DATA requires CONSTRUCTIVE - Z interference
• e +P DATA requires DESTRUCTIVE interference
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 11/35
Neutral Current DIS - Reduced Cross SectionNeutral Current DIS - Reduced Cross Section
• SM shows good agreement with data over all Q2 range
2
2
2
4 1
2~
dxdQ
d
Y
xQ NC
NC
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 12/35
Neutral Current DIS - Reduced Cross SectionNeutral Current DIS - Reduced Cross Section
2
2
2
4 1
2~
dxdQ
d
Y
xQ NC
NC
• High Precision at low to medium Q2, x
• First measurements at high Q2 and x
- Z interference seen xF3
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 13/35
Neutral Current DIS - FNeutral Current DIS - Fl l ExtractionExtraction
Bjorken y < 0.75
H1 data extend to small electron
energies
),(),(),(2)( 222
32
24
2
2
2
QxFyQxxFYQxFYxQdxdQ
ped NCL
NCNCNCBorn
y2 FL small at high Q2 Need high y
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 14/35
Neutral Current DIS - xFNeutral Current DIS - xF33
• First extraction of xF3 on PROTON at high Q2, x
Direct Sensitivity to the valence quarks!
820920
1
920
920
820
820
2
4
3
11
2 YYY
Y
Y
YxQxF
),(),(),(2)( 222
32
24
2
2
2
QxFyQxxFYQxFYxQdxdQ
ped NCL
NCNCNCBorn
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 15/35
Charged Current DIS Structure FunctionsCharged Current DIS Structure Functions
Q2
Xpe
))(1(2
2
2
22
22
2
2
sdycuMQ
MG
dxdQ
d
W
WF
Xpe
))(1(2
2
2
22
22
2
2
sdycuMQ
MG
dxdQ
d
W
WF
• Sensitivity to separate parton densities
• Effect of W mass - from propagator
Probe d valence
Probe u valence
Reduced Cross Section
2
2
2
22
2
2~dxdQ
d
M
MQ
G
x
W
W
FCC
W exchange
L.O. CROSS SECTIONS
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 16/35
Charged Current DIS -Charged Current DIS - 2/ dQd
• Effect of different parton densities seen from lower Q2
• Factor of 10 difference in e+/e- cross section at high Q2
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 17/35
Charged Current DISCharged Current DIS
• Need for more d at high x ?
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 18/35
Charged Current DISCharged Current DIS
sdycux
sdycux
Pe
Pe
2
2
1~
1~
CC
CC
xdyxuPePe 2CCCC 1 versus :
• Possibility to extract d/u using proton as target - Higher Statistics
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 19/35
Charged Current DIS - Fitting MCharged Current DIS - Fitting MWW
02CC0 Q
PDF Sys.; Stat.; :Errors
GeV 330272481 :Z
GeV 737133980 :H1
for of shape Fit2
....
....
W
W
W
M
M
MdQ
dσ
tZ
W
tZW
mMM
M
mMMMfG
,,
.
,,;
.
...
.
...
H
030060
300310
130160
240250
H
PDF; Sys.; Stat.; :Errors
GeV 5080 :Z
:constraint Model Standard
Consistency check rather than a measurement of MW
August-99 world average:
MW = 80.376 0.039 GeV
2
22
22
2
W
WF
CC
MQ
MG
dQ
d
Q2 dependence of CC cross section includes propagator
term
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 20/35
Searches for New PhysicsSearches for New Physics
The High Q2 / PT Range Accessible at HERA allows the competitive searches in many
areas for New Physics.
Some of the Topics Covered
• W/Z production - High PT Leptons
• Single Top Production
• New Lepton-Quark Interactions
• Excited Fermions / Quark Substructure
• SuperSymmetry - Talks from U. Heintz & M. Chertok
Ob
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atio
n o
f E
ven
ts a
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igh
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rvat
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of
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at
Hig
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ith
Iso
late
d M
uon
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ith
Iso
late
d M
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s
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ZE
US
H1
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 22/35
Isolated High PIsolated High PTT Leptons Leptons
A class of Interesting events at HERA
Sensitivity to rare Standard Model Processes
Single - W Production
pbXeWep 0.1) ( e e’
/ Z0
q
q
W
New Physics
Leptonic decay of W events with a high energy lepton and missing transverse momentum
NLO calculations are underway M. Spira
t~
b~
e
d
l
d
W Stop and Sbottom production
R-Parity Violating Supersymmetery
Single Top production through anomalous flavour changing Neutral Current Coupling (FCNC)
t
b
cu,
l
W
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 23/35
Isolated High PIsolated High PTT Leptons Leptons
W l Kinematics
22YX
CALT PPP
lT
CALT
XT PPP -
hltyAcoplanari
))cos(1(2 M T Tl
T PPMassTransverseCAL
TT PP e,for track
TX
TT PPP
,for
Expect a peak at W mass for W l
Acoplanarity
Neutrino
Jet
Lepton
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 24/35
H1 Isolated High PH1 Isolated High PTT Leptons Leptons
H1 94-00e+p 101.6 pb-1 Electrons Muons E+
combined
PTX> 0 GeV 10 / 7.9 +/- 1.9 8 / 2.6 +/- 0.7
18 / 10.5 +/-2.5(only W 8.2)
PTX> 12GeV 5 / 2.6 +/- 0.7 8 / 2.6 +/- 0.7
13 / 5.1 +/-1.3(only W 4.2)
PTX> 25 GeV 4 / 1.3 +/- 0.3 6 / 1.5 +/- 0.4
10 / 2.8 +/-0.7(only W 2.3)
PTX> 40 GeV 2 / 0.4 +/- 0.1 4 / 0.6 +/- 0.2
6 / 1.0 +/-0.3(only W 0.93)
0 Events found with electron running
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 25/35
ZEUS - Isolated High PZEUS - Isolated High PTT Leptons Leptons
Search for high PT tracks in high PTCAL sample
• PTCAL > 25 GeV
• Pttrack > 10 GeV
22/D Jettrack
ZEUS Preliminary1994-2000
ElectronsObserved/expected
(W)
MuonsObserved/Expected
(W)
e+p 114 pb-1 7 / 9.9 1.6 (2.4) 7 / 4.6 0.6 (1.1)
e-p 16 pb-1 3 / 1.1 0.4 (0.3) 0 / 0.8 0.1 (0.2)
TOTAL 130 pb-1 10 / 11.0 1.6 (2.7) 7 / 5.4 0.7 (1.3)
Check Isolation of high Pt
track wrt to other tracks (Dtrack)
and Jets (Djet)
Event Rate Consistent with SM Prediction
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 26/35
Comparison ZEUS - H1Comparison ZEUS - H1
H1(101 pb-1)
e+p data only18/10.5 (W 8.2)
High Purity/Efficiency
H1(115.2 pb-1)
e p data
18/12.3 (9.4 W)
ZEUS (130 pb-1)e p
data17 / 16.4 (4 W)
Inclusive sampleof lepton events
Selecting the same Phase Space PTX > 25 GeV
H1 (82 pb-1) 9 / 1.8 (1.5 from W)
ZEUS (130 pb-1) 2 / 2.4 (1.5 from W)
• SM expectations are in agreement
• H1 sees more events at high PTX
ZEUS has the acceptance to detect events
• Statistical fluctuation from the SM or an indication of Physics BSM? More Data Soon
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 27/35
Anomalous Single Top ProductionAnomalous Single Top Production
t
b
cu,
l
W
Single-top production with anomalous FCNC coupling
MissTT P Jet Phigh lepton)( lbWt
ZEUS Leptonic Channel:
Final state with high PT Lepton and large PT
X
• ZEUS Dtrack > 0.5, Djet> 1.0 and PT
X > 40 GeV
• ZEUS sees no events
H1 Leptonic Channel:
Final state with high PT (Jet) > 35 (25)Lepton and (jet) < (>) 35o
• MTlv > 10 GeV (Reject -ve leptons)
• H1 sees 5 events(3e+2) for 1.4 0.5 expected
uAqt
eut
L
Limits for Anomalous FCNC couplings
coupling
LEP e+ e- tc,tu
TEVATRON RARE TOP DECAY
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 28/35
ZEUS and H1 Isolated Lepton Control PlotsZEUS and H1 Isolated Lepton Control Plots
H1
ZEUS
Event rate consistent
with Standard
Model
Observes an excess of
Isolated High PT Events
sample
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 29/35
Search for New particlesSearch for New particles
• This presentation - Leptoquarks (LQ)
• Squarks in SUSY
• Excited Fermions
Look for the direct production of resonances with Mass M < s
Look for deviations in SM cross section - CONTACT Interactions
PR
Leptoquarks (LQ)
• Scalar and Vector, colour triplet bosons
• Carry Fermion number F=3B+L=0,2
Decays - Look for Resonances in e q system
Generic Models LQ l q
LQ q
s
Mq
sJ LQ
22
4)1(
LQ
q
, e
q
e
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 30/35
Resonance Hunting 1Resonance Hunting 1
e e’
/ Z0
q q
e
q
e
q
LQ
NC DIS SCALAR LQ:SUSY R in q~or P
2
1
ydy
d
FLAT
SCALARdy
d
Intriguing HERA events caused
excitement in past years
What About New DATA ?
Me / MCJ
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 31/35
Resonance Hunting 2Resonance Hunting 2
Analysis of Latest 1999 -2000 Data
Excess in old data not confirmed by New DATA H1 / ZEUS Derive Limits on LQ couplings and Masses MLQ (In BRW Model)
LEP -Virtual effects to hadronic xsec
Tevatron - LQ produced via strong coupling
HERA - Stringent limits for intermediate mass range
y21cos *
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 32/35
Limits from New DataLimits from New Data
Quick look at Contact Interactions
• Large Mass Leptoquarks - See Previous
• Large Extra Dimensions - Kaluza-Klein Gravitons
• Compositness - Quark Radius
scale) (process s whichin expected xsec NC oneffect for Look
...),(),(1)( 2222
2ηη QxBQxAdxdQ
d
dxdQ
d SM
Kaluza-Klein Graviton Exchange - Effective contact interaction
4/ SG M
H1
M-S > 0.93 TeV
M+S > 0.63 TeV
ZEUS
M-S > 0.82 TeV
M+S > 0.81 TeV
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 33/35
Contact InteractionsContact Interactions
Quark form factor:
2
2
22 61 Q
R
dQ
d
dQ
d qSM
Rq - quark radius
ZEUSRq <0.73 x 10-16 cm
The HERA electron
microscope probing scales to 1/1000th the
size of the proton
H1Rq <1.6 x 10-16 cm
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 34/35
The HERA UpgradeThe HERA UpgradeLuminosity Upgrade:
Large increase on present luminosity
Running Programme:
Five years of running
starting in September 2001
1000 pb-1 for both H1 / ZEUS
Polarisation for Collider Experiments:
Longitudinally Polarised electron/positron beams
60% (design goal)
Measurements of NC and CC DIS using high luminosity and
upgraded detectors will constrain:
Singlet, non-singlet quark densities
u, d, s (CC DIS)
c, b, g (NC DIS)
i.e. COMPLETE study of proton structure
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 35/35
- The Structure Function F2 1000 pb-1
1000 pb-1
x = 0.65
Q2 = 4 104
Future PhysicsFuture Physics
Opportunities for a discovery
To complement those at the Tevatron
High precision Structure Function
measurements - high x
constraints important for high energy processes at
Tevatron and LHC
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 36/35
Summary - Summary - HERA High QHERA High Q22 Physics Physics
• Results shown of High Q2 NC + CC cross sections - with high statistics data sets (e- & e+)
• Wealth of Data + measurements allowing tests of QCD and Electroweak parameters
• The recent 16 pb-1 electron data has allowed the first extraction of xF3 the last unmeasured proton structure function - Effect of - Z interference observed
• High Q2 cross sections are well described by the Standard model - a triumph for QCD
• Opportunity to constrain pdfs (d/u ratio) at high x possible with clean proton target
•Need for forth coming higher statistics to improve Charged Current xsec and better constraint on the high x valence pdfs - xF3
• Oportunity for discovery (LQ)
• More Isolated Leptons ?
The HERA Upgrade
PIC 2001 - 28th June 2001 High Q2 Physics - C.M. Cormack 37/35
Neutral Current DIS - xF3 Extraction
820920
1
920
920
820
820
2
4
3
11
2 YYY
Y
Y
YxQxF
3820
2820
4
2
2
2 2xFYFY
xQdxdQ
d
3920
2920
4
2
2
2 2xFYFY
xQdxdQ
d
• Error limited by electron sample (16 pb-1)
• Positron data sample (30 pb-1)
Extraction Method
),(),(),(2)( 222
32
24
2
2
2
QxFyQxxFYQxFYxQdxdQ
ped NCL
NCNCNCBorn
Sign of xF3 term depends on lepton charge y2 FL small at high Q2