Tracey Pratt Durham Exotics Workshop Large Searches at CDF, Tevatron Tracey Pratt Liverpool University Extra Dimensional models Tevatron and the CDF detector Run I & Run II searches Future reaches at the Tevatron Questions Conclusions and outlook March 2003
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Tracey Pratt Durham Exotics Workshop Large Searches at CDF, Tevatron Tracey Pratt Liverpool University Extra Dimensional models Tevatron and the CDF.
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Tracey Pratt Durham Exotics Workshop
Large Searches
at CDF, Tevatron
Tracey PrattLiverpool University
Extra Dimensional models Tevatron and the CDF detector Run I & Run II searches Future reaches at the Tevatron Questions Conclusions and outlook
March 2003
Tracey Pratt Durham Exotics Workshop
Extra dimensional solutions to the hierarchy problem (MEW << MPlanck?)
G
Many large extra dimensions (n=2-7)
gravity freely propagates in the ED
Taking the compact space to be very large Curvature of the extra dimension
1 highly curved extra dimension
gravity localised in the ED
Scale of physical phenomena on the TeV-brane is specified by the exponential warp factor:
= Mple-kRc
~ TeV if kRc ~11-12.
Planck TeV brane
for n 2, Rc < 1 mm
Vn = 2Rcn
MPl(4+n) ~ 1 TeV
MPl2 = VnMPl(4+n)
(2+n)
requires Rc ~ 10(30/n –19) m
To solve hierarchy choose
Torus
Tracey Pratt Durham Exotics Workshop
Searching for ED
New Parameters (Hewett formalism)
1. Ms
2. , dimensionless parameter, 1
Since gravitons can propagate in the bulk, energy and momentum are not conserved in the GKK emission from the point of view of our 3+1 space-time
Since the spin 2 graviton in generally a has a bulk momentum component , its spin from the point of view of our brane can appear as 0, 1 or 2
Gravitons, do not interact with the detector, and radiate into the bulk, appearing as missing energy:
jet + MET + MET
Cross section depends on the number of ED
Run I
M (GeV)
2) Graviton exchange: virtual contribution to the scattering processes Deviations in cross sections and asymmetries of SM processes e.g. qq-bar l+l-, Or new processes e.g. gg l+l-, Cross section independent of the number of ED in Hewett formalism
Gupta et. al. hep-ph/9904234
=+1
1) Direct GKK emission in association with a vector-boson
New Parameter
MD = MPl(4+n)
Tracey Pratt Durham Exotics Workshop
Searching for ED
700 GeV KK Graviton at the Tevatron
k/MPl = 1,0.7,0.5,0.3,0.2,0.1 from
top to bottom
Mll (GeV)
RS model
Dilepton channel
400 600 800 1000
Mll (GeV)
10-2
10-4
10–6
10-8
10-2
10-4
10-6
10-8
10-10
Tevatron 700 GeV KK graviton
d/dM (pb/GeV)
couplings of each individual KK excitation are determined by the scale, = Mple-kRc ~ TeV. masses mn = kxne-krc (J1(xn)=0)
Via virtual exchange
Davoudiasl, Hewett, Rizzo hep-ph0006041
200 400 600 800 1000 1200
1000 3000 5000
10.50.10.050.01
10.70.50.30.20.1
KK excitations can be excited individually on resonance
The cleanest signature for graviton resonance production is an excess of events in the dilepton or dijet channel.
1500 GeV GKK and subsequent tower states
K/MPl
New parameters:
1. First graviton excitation mass: m1
2. A ratio: k/Mpl
= m1Mpl/kx1,, 1 = m1 x12 (k/Mpl)2
LHC
Tracey Pratt Durham Exotics Workshop
CDFRun I (1992-1996)
L ~ 110 pb-1 s 1.8 TeV
Run II (2001-2006)
L ~ 2000 pb-1 s 2 TeV
Tevatron pp collider Highest energy collider operating in the world!
D0
p
980 GeV/c2 980 GeV/c2
s 2 TeV
u ud
p
u ud
20 x more events
8
Tracey Pratt Durham Exotics Workshop
CDF at the Tevatron
Highlights of UpgradeImproved triggerImproved silicon trackerImproved central outer trackerNew forward calorimetersExtended muon coverageTime of flight detectorEM calorimeter timing (Summer 03)
Run I Run II
Taking physics quality data since February 2002
Muon System
COT
Plug Calorimeter
Time-of-Flight
Central Calorimeters
Solenoid
Silicon Tracker
Tracey Pratt Durham Exotics Workshop
CDF ED Searches
Emission Channels
+ MET , jet+ MET
Exchange
Diphoton,
Dielectron
and combined
Dimuon
Dielectron
and combined
(Diphoton)
(Dijet)
Run I
Run II
Tracey Pratt Durham Exotics Workshop
Run I GKK emission: Et
Limitsn=4 MD > 0.55 TeV
n=6 MD > 0.58 TeV
n=8 MD > 0.60 TeV
qq GKKSearch Selection - One with ET > 55 GeV and ||<1 - Missing ET > 45 GeV - No jets with ET > 15 GeV - No tracks with pT > 5 GeV
ResultsExpected background: 11.0 2.3 Observed: 11
Cosmic ray muons 6.3 2.0
Z0+ 3.2 1.0
W e (““) 0.9 0.1
Prompt diphotons 0.4 0.1
W () 0.3 0.1
Main backgrounds
87 pb-1
Tracey Pratt Durham Exotics Workshop
EM calorimeter timing
Exp
ect e
d nu
mbe
r of
eve
nts
wit h
tim
i ng
22 GeV
55 GeV
EM Calorimeters
Hadronic
Reducing the kinematic requirement would increase the signal by a factor of 2.8
And decrease cosmic ray background
Tracey Pratt Durham Exotics Workshop
Real GKK emission : jets+Et
from Pythia
prediction from Giudice, Rattazi and Wells (hep-ph9811291)
falls as 1/MDn+2 for all subprocesses
Tevatron s=2 TeV MD = 1.2 TeV
n=4
n=2
pTmin (GeV)
gggGKK
qggGKK
qqgGKKdominate sub-process for n>2
q q q q q q
q
qq gg gg
GKKGKKGKK
gg
gg
g
gg
g
g
g
g
GKKGKKGKK
GKKGKK GKK
q
qqq
qqq
gg gg
q q
g
Tracey Pratt Durham Exotics Workshop
Search Selection Jet ET
1st 80 GeV, || <1.1 and ET>80 GeV
a second jet is allowed if ET2nd > 30 GeV
no isolated tracks in event (pT10 GeV)
Main background Z()+jets, W()+jets.
MD (GeV) >
n CDF(K=1.0) D0(K=1.0) D0(K=1.34)
2 995 886 987
4 768 663 728
6 707 626 646
Best limits from the Tevatron from
searches for direct graviton emission
Run Ib GKK emission: jets+ET
ResultsExpected: 27416 Observed: 284 events.Relative uncertainty on the signal acceptance 25 %
Limits95 % C.L. upper limit on number of signal events: 62
Tracey Pratt Durham Exotics Workshop
Predicted results for GKK emissionjet+ET
n CDF Run I results (GeV)
MD reach
Run I (GeV)
MD reach
Run II >300pb-1
(GeV)
MD reach
LHC 100 fb-1
(TeV)
2 995 1100 1400 8.5
3 950 1150 6.8
4 768 850 1000 5.8
5 700 900 5.0
hep-ph 9811291 (1999)
Bounds obtained by requiring
Tevatron: signal>205 fb (for s=2 TeV) with the acceptance cuts |jet|<3 and EminT, jet = 150 GeV.
LHC: signal>2.6 fb (for s=14 TeV) with the acceptance cuts |jet|<3 and EminT, jet = 1 TeV.
G. Giudice, R. Rattazzi, J. Wells
|jet|<1.1 and EminT, jet = 80 GeV
Tracey Pratt Durham Exotics Workshop
Virtual Graviton Exchange
Clean experimental signature. Low backgrounds
/Z0l-q
q
+ +q
q
g
g
l+
l-
l+ l+
l-
KKn KKn
Diphoton Channel
gg initiated process
Dilepton Channel
Extra Dimensions
Standard Model
+
+
+
Tracey Pratt Durham Exotics Workshop
Fit method used
A 3 parameter (nSM, nBG, ) unbinned likelihood function is used to extract
Generate MC templates for each piece independent of the choice of and s
4.
KLED applies to the LED terms of the cross section, to estimate the effect of non-leading orders in LED.
No estimate of KLED; so results quoted for KLED=1.0 (no correction) and 1.3 (SM-like)
KLED
103
102
101
10 200 400 600 800 1000 1200
M (GeV/c2)
even
tsParameterise the cross section in terms of = / s4
= SM + INT + 2 KK BG
Tracey Pratt Durham Exotics Workshop
CDF Run I search for LED
Search Selection
2 with Et > 22 GeV,
CC or CP: central (|| < 1), plug (1<|| <2.4)
Main backgrounds: fakes from -jet and jet-jet
Results Observed: 287 Central Central events
192 Central Plug eventsLimits Using a maximum likelihood fit method
CC 100 pb-1, CP 87 pb-1
2.
Plug
Central
95 % C.L. MS > 899 / 797 GeV KLED = 1.0
( = -1/+1, Hewett)
Mhighest = 288 GeV/c2
Tracey Pratt Durham Exotics Workshop
CDF Run I ee search for LED2 high Et isolated electrons (> 25 GeV) (CC and CP)
Main Backgrounds: Drell-Yan, QCD di-jet, diboson production, Z,tt-bar production
500 GeV
CC: 3319 CP: 3825
Tracey Pratt Durham Exotics Workshop
CDF + ee search for LED
Channel 95 % C.L. MS (Hewett)
KLED = 1.0 KLED = 1.3
= -1 = +1 = -1 = +1
ee 780 768 826 808
899 815
ee and
905 826 939 853
Diphoton channel is more sensitive to LED than dielectrons,
•because the LED production cross-section is higher
•The LED dielectron analysis has a 500 GeV ee event which is more consistent with LED than the SM.
CDF found that a 2 dimension fit in both invariant mass and angular distribution only gave a slight improvement over the 1-dimensional fit in their statistically limited samples.
Tracey Pratt Durham Exotics Workshop
Run II GKK exchange reaches
HLZ notation: hep-ex 0008065 D0 results: ADDCorresponds to R < 0.3 mm (n-2) and R < 2 fm (n=7)
D0 Collab. hep-ex 0008065
Run I, 0.13 fb-1 2 fb-1 20 fb-1 LHC, 100 fb-1
1.3 TeV 1.9 TeV 2.6 TeV 9.9 TeV
n=7-2 extra dimensions
Tevatron
Cheung hep-ph 0003306
95 % C.L. sensitivity limits on Ms (HLZ)
n=4e+e- + +- +
Using double differential cross-sections
HLZ formalism: sign of interference fixed, interference term is ~ F / MS
4, where F reflects the number of ED
F = log(MS2/2) , n=2 F = 2/(n-2), n>2
= F . MS
4(Hewett) 2 MS4(HLZ)
2 fb-1 20 fb-1
Tracey Pratt Durham Exotics Workshop
CDF ED Searches
Emission Channels
+ MET , jet+ MET
Exchange
Diphoton,
Dielectron
and combined
Dimuon
Dielectron
and combined
(Diphoton)
(Dijet)
Run I
Run II
Tracey Pratt Durham Exotics Workshop
Initial Run II limits: ee,
pb-1
100 200 300 400Dimuon mass (GeV/c2)
102
101
1
10-1
10-2
Eve
nts
/ 5
GeV
ICHEP 2002
Tracey Pratt Durham Exotics Workshop
limits 72 pb-1
Search selection2 isolated PT>20 GeV/c, ||<1Cosmic ray rejection cuts
ResultsObserved 775 events
Signal region above 150 GeV/c2 observed 4 eventsLimits95 % C.L. upper limit on number of signal events: 5.6
K=1.3
208 GeV/c2
Tracey Pratt Durham Exotics Workshop
Run II cosmic ray rejectionusing the Time-of-Flight detector
Remove cosmic rays with a cut requiring Tupper – Tlower > -5 ns