Post on 22-Dec-2015
transcript
DDDiffractive Results from
Workshop on low x physics, Antwerp 2002
Brian Cox
E
• Diffractive W and Z
• Observation of double diffractive dijets
• Run 1 highlights
• Run II Beginnings
Central Calorimeter
End Calorimeter
Hadronic Calorimeter
EM Calorimeter
L0 Detector
beam
nL0 = # hit tiles in L0 detector
ncal = # cal towers with energy above threshold
Energy Threshold coverage EM Calorimeter 150 MeV 2.0<||<4.1 Had Calorimeter 500 MeV 3.2<||<5.2
Diffraction in the DØ detector
Diffractive W and Z production DDCentral and Forward electron W Event and Z event selections: Start with Run1b W e and Z ee candidate samples
DØ Preliminary
Diffractive selection DD•Measure forward calorimeter tower multiplicities in range 3.0<||<5.2
•Look at minimum multiplicity side of detector (not necessarily opposite side to electron)
Central W Multiplicity DD
-1.1 0 1.1 3.0 5.2
Minimum side
ncal
L0nL0
ncal
Peak at (0,0) is diffractive W-bosonSignal: 68 of 8724 events in (0,0) bin
DØ Preliminary
Forward W multiplicity DD
-2.5 -1.1 0 1.1 3.0 5.2
Minimum side
L0nL0 ncal
Peak at (0,0) indicates forward diffractive W-boson in forward electron sample:23 of 3898 events in (0,0) bin
DØ Preliminary
Central W event distributions DD
DØ Preliminary
Standard W Events Diffractive W Candidates
ET=37.12
ET=35.16
ET=36.08
MT=70.64 MT=70.71
Electron ET
Neutrino ET
Transverse Mass
ET=35.27
Z multiplicity
DØ Preliminary
-2.5 -1.1 0 1.1 3.0 5.2
Minimum side
ncal
L0
DD
Peak at (0,0) indicates diffractive Z-boson:9 of 811 events in (0,0) bin
Extracting the Signal DD•2-D fits of multiplicity plots
32 //
32
1 sysx eess
sS
xybybxbbB 3210
Data Fit
Fit SignalFit Background
Use high statistics background DD
Solid line: Central W Dashed: Cen+Fwd
W
ncal
Solid line: Central W Dashed: Cen+Fwd W
ncal
DØ Preliminary Background shapes agree, but fit more reliable with higher stats
Results DD
Sample Diffractive Probability Background All Fluctuates to Data Central W (1.08 + 0.21 - 0.19)% 1 x 10-13 7.7Forward W (0.64 + 0.19 - 0.16)% 6 x 10-7 5.3All W (0.89 + 0.20 – 0.19)%Z (1.44 + 0.62 - 0.54)% 5 x 10-5 4.4
DØ Preliminary
*Observed clear Diffractive W and Diffractive Z signals*Measured Diffractive W/All W and Diffractive Z/All Z
CDF {PRL 78 2698 (1997)} measured RW = 1.15 ± 0.55% with a significance of 3.8
A challenge to the Monte Carlos: DD
DØ Preliminary
W + jet and forward / central W production rates
Sample Data Quark Hard Gluon Cen W (1.08 + 0.21 - 0.19)% (4.1 0.8)% (0.15 0.02)%For W (0.64 + 0.19 - 0.16)% (7.2 1.3)% (0.25 0.04)% Z (1.44 + 0.62 - 0.54)% (3.8 0.7)% (0.16 0.02)%
Jet ET Data Quark Hard Gluon>8GeV (10 ± 3)% 14-20% 89 %>15GeV (9 ± 3)% 4-9 % 53 %>25GeV (8 ± 3)% 1-3 % 25 %
W + jet rates : very sensitive to IP structure
Gaps Between Jets
jet
jet
2.14.3)Data(6301800 R
DD
Cox, Forshaw & Lonnblad, JHEP10 (1999) 023
Enberg, Ingleman & Motyka Phys. Lett. B524:273-282,2002
Diffractive Dijets at 630 and 1800 GeV
-4.0 -1.6 -1.0 1.0 3.0 5.2
orMeasure Multiplicity here
Data Sample Measured Gap Fraction 1800 Forward Jets 0.65% + 0.04% - 0.04% 1800 Central Jets 0.22% + 0.05% - 0.04% 630 Forward Jets 1.19% + 0.08% - 0.08% 630 Central Jets 0.90% + 0.06% - 0.06%
* Forward Jets Gap Fraction > Central Jets Gap Fraction
* 630 GeV Gap Fraction > 1800 GeV Gap Fraction
Forward jet trigger
ET > 12 GeV
Central jet trigger
ET > 15 (12) GeV @ 1800 (630) GeV
DD
• Monte Carlo analysis (hep-ex/9912061) – gluon dominated IP (hard + soft) + reduced flux factor accounts for data
DDDiffractive Dijets at 630 and 1800 GeV
s = 1800 GeV forward
central
s = 630 GeV forward
central
i
yT
s
eE i
i
The Run II Pots DD
• 8 detectors fully installed (D1, D2, A1I, A2I, P1U, P1D, P2D)
• All will be in place after October shutdown