Transcript Jets and QCD in D0 Experiment Physics at Extreme Energies Hanoi, Vietnam July 23, 2000 V.

Jets and QCD in
D0 Experiment
Physics at Extreme
Energies
Hanoi, Vietnam July 23, 2000
V. Šimák
Institute of Physics ASCR, Prague
for the D Collaborations
T itle:
d0logo.eps
Creator:
CLARIS EPSF Export Filt er V1.0
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded in i t.
Comment:
T his EPS pic ture wi ll print to a
Pos tScri pt print er, but not to
other t ypes of printers.
Outline
p p  J1 (J2)  anything
d 2
dET d
• Inclusive Jet Cross Section :
– at 1800 GeV
– at
630 GeV
– Ratio of Inclusive Jet Cross Sections
• Dijet Triple Differential Cross Section
d 3
dET d1d2
• Dijet Mass Spectrum
f a / A x1 
All theoretical
comparisons done
jet1
x1P1
P1
with JETRAD
P2
̂  s 
f b / B  x2 
x2 P2
jet 2
 (p1p2  2 jets) 
  dx dx f x  f x ˆ (ab  cd )
1
2 a/ A
1
b/ B
2
abcd
Hanoi, July 23,
2000
V. Šimák
2
y
_
p
p
x
z
  - ln [ tan (q / 2) ]
|| < 4.2
l int> 7.2 total)
Transverse
segmentation
D x D   0.1 x 0.1
Electrons: E / E = 15% /  0.3%
Pions:
E / E = 45% /  4%
Inclusive Jet Cross Section at
s = 1800 GeV
0.
±8%
Hanoi, July 23,
2000
12%
-10%
V. Šimák
24%
-20%
4
Inclusive Jet Cross Section at
s = 1800 GeV (D)
0.
• JETRAD mF= mR= ETMax /2 ,
Rsep=1.3, for ||< 0.5
For all PDF’s probabilities
between 47-90%
Hanoi, July 23,
2000
V. Šimák
5
Inclusive Jet Cross Section at
s = 630 GeV
-1
Ldt
=
536
nb

Hanoi, July 23,
2000
0.
V. Šimák
6
Inclusive Jet Cross Section at
s = 630 GeV
• Some discrepancy at low ET, errors are
large , but there is overall agreement.
Hanoi, July 23,
2000
V. Šimák
7
Ratio of Inclusive Jet Cross Sections
Same discrepancy exists in ratio of the scaled
cross sections.
QCD predictions seem to be 20% higher than
expected.
Hanoi, July 23,
2000
V. Šimák
8
Dijet Triple Differential Cross
Section
1994-1995 Collider run (run 1b):
 Ldt
=92
± 6 pb-1
preliminary results
Require at least two reconstructed jets
Trigger Jet: ET > 60 GeV
Probe Jet : ET > 30 GeV
No restriction on additional jets.
Measurement as input to PDF’s:
gluon distribution is most interesting.
Both experiments use JETRAD for
theoretical comparisons with different
PDF’s.
Hanoi, July 23,
2000
V. Šimák
9
Dijet Triple Differential Cross
Section (D)
OS
SS
Beam line
• Divide data sample into four eta bins:
-- 0.0<||<0.5, 0.5<||<1.0, 1.0<||<1.5,
1.5<||<2.0
• Divide each eta bin into two subsamples:
-- events with 2 jets on the Opposite Side (OS)
-- events with 2 jets on the Same Side (SS).
• ET of both jets are measured so there are two entries
per event into each of the eight the cross sections.
• JETRAD using m = E/2
Note that the renormalization and factorization scale
are chosen to be:
-- mf = mr = E/2 ( max jet )
Hanoi, July 23,
2000
V. Šimák
10
Dijet Triple Differential Cross
Section (D)
0.0<||<0.5
1.0<||<1.5
0.5<||<1.0
1.5<||<2.0
Hanoi, July 23,
2000
V. Šimák
11
Dijet Triple Differential Cross
Section (D)
m = ET/2
0.0<||<0.5
0.5<||<1.0
1.0<||<1.5
1.5<||<2.0
Hanoi, July 23,
2000
V. Šimák
12
Dijet Triple Differential Cross
Section (D)
m = E/2
0.0<||<0.5
0.5<||<1.0
1.0<||<1.5
1.5<||<2.0
Hanoi, July 23,
2000
V. Šimák
13
Dijet Triple Differential Cross
Section (D)
m = E/2
0.0<||<0.5
0.5<||<1.0
1.0<||<1.5
1.5<||<2.0
Hanoi, July 23,
2000
V. Šimák
14
Dijet Mass Distribution
Mi 
M i 
1
Mi
Ei1 Ei 2 1 - co sq i12 
Ei1Ei 2
 Ei 2Ei1 1 - co sq i12 
Smeared Cross
Section
Unsmeared
f  M    F  M     M  - M , M  dM 
where

F  M    AM 
M
M
 9% @ 100 GeV
 4.5% @ 1000 GeV
Hanoi, July 23,
2000
V. Šimák

M 
1 

s
-B 
C
200-220 GeV: 8% Error
800-1400 GeV: 30% Error
15
“Typical DØ Dijet Event”
MJJ = 1.18 TeV
Q2 = ET,1×ET,2=
2.2x105 GeV2
ET,1 = 475 GeV, 1 = -0.69, x1=0.66
ET,2 = 472 GeV, 2 = 0.69, x2=0.66
Hanoi, July 23,
2000
V. Šimák
16
Hanoi, July 23,
2000
V. Šimák
17
Compositeness Contact Predictions
QCD +








0
0
 LL
qL m qL qL m qL    LR
qL m qL qR m qR   


0
m
0
m
 RL qR qR qL m qL    RR qR qR qR m qR   


l
l

1  q  m a q  q 

a
qL  



LL
L
L
L
m


2
2




4 


l
l




L  2 1 q  m a q
a

qR  
L  q R m
  LR  L

2
2




l
l




1
m
a
a
 RL  qR

qR  qL m
qL  


2
2





l
l




1
m
a
 RR  qR

qR  qR m a qR 


2
2





0
 XX
: singlet interactio ns
sˆ
 s 2
 1XX : octet interactio ns
X
X
X
X
 LL
  RR
  LR
  RL
 1 :
Vector  V
X
X
X
X
 LL
  RR
 - LR
 - RL
 1 :
Axial  A
Hanoi, July 23,
2000
M
V. Šimák
cosq
19
Compositeness Calculations
Eichten 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)
Suggested Scale: 1.6 TeV (LL)
PRL 77, 438(1996)
   X T eVLO
     T eVNLO
    T eVLO
 > 2.7 T eV
Hanoi, July 23,
2000
- > 2.4 T eV
V. Šimák
20
Conclusions
1800 Inclusive Cross Sec.
No significant excess
Excellent agreement with theory
630 Inclusive Cross Sec.
NLO predictions ~20% high
Experimental measurements consistent
Ratios 630/1800
NLO predictions ~20% high.
Experimental measurements consistent
Triple Differential Cross Section:
NLO QCD with recent PDF’s (CTEQ3M,
CTEQ4M, CTEQ4HJ, MRST,…) with agreement
with D0 within the systematic uncertainties
Cross sections for possible inputs to PDF’s
1800 Dijet Mass
NLO QCD in agreement with the data
Compositeness Scale > 2.4 TeV
no new physics so far
T itle:
d0logo.eps
Creator:
CLARIS EPSF Export Filter V1.0
Preview:
T his EPS pic ture was not s aved
with a preview i nc luded in i t.
Comment:
T his EPS pic ture wi ll print to a
Pos tScri pt printer, but not to
other types of printers.