Search for Compositeness at the Tevatron
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Transcript of Search for Compositeness at the Tevatron
Search for Compositeness at the Tevatron
Iain A. Bertram
Northwestern University/DØ
Talk Outline
Introduction Direct Search for Composite Quarks Contact Interaction Searches
Quark-Quark Compositeness: Dijet Events Quark-Lepton Compositeness: Drell-Yan Events
Run II Prospects Conclusion
Introduction
Three quark and lepton generations suggests that quark and leptons are composites.
Composed of PREONS. Preons interact via a new strong
interaction (Metacolour). Below a characteristic energy scale
, the preons form metacolour singlets: quarks and leptons.
Strength of interactions related to
Atom
Nucleus
Nucleon
Quark 2ˆ
s
s
Effective Lagrangian
M cos
2ˆ
s
s
Ra
RRa
RRR
La
LRa
RRL
Ra
RLa
LLR
La
LLa
LLL
RRRRRRLLRRRL
RRLLLRLLLLLL
qqqq
qqqq
qqqq
qqqq
qqqqqqqq
qqqqqqqq
L
22
22
22
224
1
1
1
1
00
00
2
A
V
1
0
Axial
:1
Vector
:1
nsinteractio o:
nsinteractiosinglet :
XRL
XLR
XRR
XLL
XRL
XLR
XRR
XLL
XX
XX
ctet
Dijet and Dielectron Variables
Dijet and di-electron Event Measure the following:
massive
massless coscosh2
2/tanln ,, :electron or Jet
221
221
2
21212,1,2
PPEEM
EEM
E
TT
T
Jet, electron 2: ET
2, 2, 2
Jet, electron 1: ET
1, 1, 1
= 0
“Typical DØ Dijet Event”
ET,1 = 475 GeV, 1 = -0.69, x1=0.66ET,2 = 472 GeV, 2 = 0.69, x2=0.66
MJJ = 1.18 TeVQ2 = 2.2x105
“Typical CDF Drell-Yan Event”
Dijet & Drell-Yan Production
1P
2P
1xfi11Px
22Px
1jet e,
2jet e,
sij ̂
2xf j
,,,ˆ
,,
2
2
2
22
2211
22
2121
RFRsij
ijFjFi
QQPxPx
xfxfdxdx
To search for compositeness we need a good prediction for Standard Model production
Dijets: NLO event generator JETRAD, Giele, Glover, Kosower Nucl. Phys. B403, 633.
Drell Yan: NNLO CalculationHamberg, Van Neerven, & Matsuura, Nucl. Phys. B359 343.
Need to choose pdf Choose Renormalization and Factorization
scales (set equal) Jets: Rsep: maximum separation allowed
between two partons to form a jet (mimic exp. algorithm)Rsep=1.3R (Snowmass: Rsep=2.0R)
2R
1.3R
Compositeness Contact Predictions
Compositeness CalulationsEichten et al., Rev. Mod. Phys. 56, 579 (84) Eichten et al., Phys. Rev. Lett 50, 811 (83)Chivukula et al., Phys. Lett. B 380, 92 (96)Lee, Phys. Rev. D 55, 2591 (97)Lane, hep-ph/9605257 (96)
= +1 + destructive interference = 1 - constructive interference Only leading order calculation:
Use to scale highest order QCD calculations.
Dijets: Use NLO Jetrad prediction as basis Drell-Yan
Use Hamburg et al., NNLO calculation as a basis.
TeV TeV
TeV NLO
LO
LO
X
M
Colorons
Colorons
(R.S. Chivukula, A.G. Cohen and
E.H. Simmons, hep-ph/9603311,Phys. Lett. B380 92 (1996)
Produces similar effects to compositeness. Motivated by technicolor Add additional SU(3) QCD type
group. Symmetry breaking between this
and standard QCD SU(3) leads to an additional set of massive gluons called colorons
Can be modeled in a similar way to compositeness:
cot cs M
Search for Excited Quarks
Search for excited quarks in dijet mass spectrum motivated by UA2’s observation of W,Z JJ (Zeit. Phys. C49)In proton anti-proton collisions.
M
Search for Excited Quarks
q qg q u d* ,
PYTHIA, f=f’=fs=1.0, =Mq*, Contact terms only.Smeared with Jet Resolutions, CTEQ3L PDF.Baur et al Phys. Rev. D42, 815 (90)
s
M
ddL
f qqg
ss
2
22
3
Search for Excited Quarks
Select data at central rapidity:
DØ: |jet| < 1.0, |jet| < 1.6
104 pb-1
Use Bayes Theorem to fit Jetrad NLO QCD prediction + q* line shape to data
CDF: |jet| < 2.0, cos < 2/3
106 pb-1
Phys. Rev. D55, 5263 (1997)
Phys. Rev. Lett. 74, 3539 (1995)
Fit data with Ansatz Function + q* line shape.
Search for Excited Quarks
DØ: Mq* > 725 GeVCDF: Exclude Mq*
up to 570 GeVbetween 580 & 760 GeV
Search for Excited Quarks
Combined LimitsMq* > 760 GeV
cos1
cos1exp
1 Measure
d
dN
N
Search for Quark-Quark Compositeness
Dijet Angular DistributionCompositeness produces excess ofevents at small and large mass
Search for Quark-Quark Compositeness
Define: Optimize for compositeness:DØ: X=4 CDF: X=2.5X
XR
events #
events #
DØ: Phys. Rev. Lett. 80, 666,1998.CDF: Phys. Rev. Lett.77, 5336, 1996,
Erratum-ibid.78, 4307, 1997
Dijet Angular Limits
DØ CDF
LL=1 2.1 TeV 1.8 TeV
LL 1 2.2 TeV 1.6 TeV
Compositeness Limits
DØ Coloron Mass LimitsMc/cot > 759 GeVV8 > 2.1 TeV
Dijet Mass Spectrum at DØ
Calculate Ratio of Cross Sections.
Analgous to R
DØ Dijet Mass Spectrum
Accepted by PRL: hep-ex/9807014
pdf Limit on
Limit on -
CTEQ3M 0.25ETmax 3.53 2.87
CTEQ3M 0.50ETmax 2.93 2.56
CTEQ3M 0.75ETmax 2.88 2.52
CTEQ3M 1.00ETmax 2.73 2.49
CTEQ3M 2.00ETmax 2.84 2.48
CTEQ4M 0.50ETmax 2.92 2.55
MRSA 0.50ETmax 2.97 2.59
LL LL1 TeV 4 TeV
Quark-Quark Compositeness Limits
Model + -
LL 2.7 TeV 2.4 TeVVVAA
3.2 TeV 3.1 TeV
V8V8 2.0 TeV 2.3 TeVA8A8 2.1 TeV 2.1 TeV
Coloron Limit: Mc/cot > 837 GeV(hep-ph/9809472)
Drell-Yan Production DØ measures the Drell-Yan Cross
section at high dielectron mass. 120 pb-1 data || < 1.1, 1.5 < || < 2.5 Submitted to PRL hep-ex/9812010
CDF measures the Drell-Yan Cross section at high dielectron and dimuon mass. 110 pb-1 data || < 1.0 Phys. Rev. Lett. 79, 2198, 1997.
High Mass Drell-Yan: Compositeness
DØ DataCDF Data
ee Mass(GeV) Events Back. Events Back.
M > 150 89 8717 17 16.50.5M > 200 26 285 7 6.240.19M > 300 6 64 2 1.450.04M > 400 1 0.90.1 0 0.430.01M > 500 0 0.20.0 0 0.140.00
Quark-Electron Compositeness Limits
CDF DØModel +
qe-
qe+
q-
q+
ql-
ql+
qe-
qe
LL 2.5 3.7 2.9 4.2 3.1 4.3 3.3 4.2LR 2.8 3.3 3.1 3.7 3.3 3.9 3.4 3.6RL 2.9 3.2 3.2 3.5 3.3 3.7 3.3 3.7RR 2.6 3.6 2.9 4.0 3.0 4.2 3.3 4.0VV 3.5 5.2 4.2 6.0 5.0 6.3 4.9 6.1AA 3.8 4.8 4.2 5.4 4.5 5.6 4.7 5.5
Run II Expectations
Assume that we will collect 2 fb-1 of data at 2 TeV M >510 GeV 2 fb-1 M >390 GeV 1 fb-1
M >300 GeV 0.25 fb-1
M >200 GeV 0.05 fb-1
Limits: V8 > 3 TeV(cf 2.3)
No Optimization
Assume Run 1 Systematics (~5%) Place limits using coloron model No optimization of bins
(M > 500 GeV>550 events < 0.5, >800 events 0.5 < < 1.0)
Conclusions
No evidence for Compositeness found at the Tevatron
QCD in excellent agreement with the data Quark-Quark Compositeness
> 2 to 3 TeV depending on modelsColorons: Mc/cot > 837 GeV
Quark-Electron Compositeness > ~ 3 to 6 TeV depending on model
Very Large Data Set in Run II: A Good Opportunity to find New Physics....