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)
95 % C.L. MS > 780 / 768 GeV ( = -1/+1, Hewett) KLED = 1.0
95 % C.L. MS > 826 / 808 GeV ( = -1/+1, Hewett) KLED = 1.3
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
Tupper – Tlower
~ 2L/c for cosmic ray dimuons
~ 0 for interaction dimuons
Time resolution 100 ps
Cosmic ray muonsInteraction muons
rz
Tupper
Tlower
Tracey Pratt Durham Exotics Workshop
Run II ee search 72 pb-1
371 GeV
Search selection2 isolated e (CC, CP)ET>25 GeV
ResultsObserved: 4576 ee events
Above 200 GeV/c2 observed 27, expected 16 8 Above 350 GeV/c2 observed 3, expected 1.1 0.3
Tracey Pratt Durham Exotics Workshop
ee better limits than in channel, because
plug gives e a larger acceptance and a higher efficiency per event
Run II ee search 72 pb-1
3,e0
42,
95 % C.L. Excluded region
K=1.3
Tracey Pratt Durham Exotics Workshop
Run II ee + search 72 pb-1
95 % C.L. Excluded region K=1.3
Tracey Pratt Durham Exotics Workshop
CDF model searches
Future:
Add more of the detector acceptance
Use Run II dijet and diphoton searches to set RS limits
25
55
0
42
||<0.6
||<1
||<1.5
Tracey Pratt Durham Exotics Workshop
Run II dijet search at CDF
Inclusive Jet samples2 highest ET jets selected
Fit of the mass spectrum with a simple background parameterisation and search for bumps comparable with mass resolution
No significant evidence for a new particle
Highest mass event 1364 GeV/c2
ET=666 GeV (corr)
583 GeV (raw)
=0.31 (detector)=0.43 (correct z)
ET=633 GeV (corr)
546 GeV (raw)
=-0.30 (detector)=-0.19 (correct z)
z vertex = - 25 cm
z
Tracey Pratt Durham Exotics Workshop
Run II diphoton search
Results
Highest mass event is: 168 GeV/c2
Above 150 GeV/c2: Observed 2 events
Expected 3.3 events
Search selection
Isolated with ET > 13 GeV, || < 0.9
No 3D tracks pointing to em cluster
No excess observed at high invariant mass
Main backgrounds
fakes from -jet and jet-jet,
where jet fragments into a hard 0
Tracey Pratt Durham Exotics Workshop
Davoudiasl, Hewett, Rizzo hep-ph 0006041
constraints
m1 (GeV)
K/MPl
0.20
0.10
0.07
0.05
0.03
0.02
0.01
Tevatron 110 pb-1
Dijet and dilepton data
1000 2000 3000 4000 5000
Oblique Parameters
< 10 TeVSolve hierarchy
|R5| < M52
Curvature of 5th dimension
LHC 10 fb-1
Dilepton data
Allowed Region
2 fb-1
Sridhar hep-ph 0103055
Diphoton data
2 fb-1
Tracey Pratt Durham Exotics Workshop
Outstanding Questions? ?
Is ADD model graviton exchange in Pythia ?MC program by Ulrich Baur, but no interference between the SM gg box diagrams and the tree-level gg graph
Has been calculated by Eboli et al (hep-ph/9908358) Included as a systematic uncertainty (Sys
INT) at present (Sys
INT = 34 % SysTotal for=-1, 43 % for =+1)
1.0 as for no loop corrections ?
or 1.3 like in the SM ?
Justified? Not clear, since the NLO processes including gravitons are quite different than the SM NLO QCD processes
=SM + KLED(INT+2KK)
What should the k-factor used for ED searches
Tracey Pratt Durham Exotics Workshop
Conclusions and outlook
Searches performed in several channels at CDF No evidence of deviations from Standard Model expectation observed Best limits obtained
ADD jets+ET, ee + ~ 1 TeV
RS ee + m1 ~ 365 to 550 GeV for k/MPl 0.05 to 0.1
Tevatron Run II has successfully started, the first CDF Run II results already determined and .. to be updated in the future…
Tevatron Run IIa (2 fb-1) has a promising observation potential and should be in a position to discover ED, if they exist,
ADD: up to about MS = 2 TeV
RS: m1 from 0.5 to 1 TeV for k/MPl 0.01 to 0.1
Tracey Pratt Durham Exotics Workshop
THE END!
Tracey Pratt Durham Exotics Workshop
Jets+MEt
Process
MD = 1 TeV
n2(pb)
Total)
n(pb)
Total)
n(pb)
Total)
qq-bargGKK 4.1
(0.16)
1.6
(0.53)
0.70
(0.78)
qggGKK 9.6
(0.38)
0.68
(0.22)
0.096
(0.11)
qggGKK 11.4
(0.45)
0.77
(0.25)
0.11
(0.12)
Total 25.2 3.05 0.90
cdf5151
Tracey Pratt Durham Exotics Workshop
CDF ll/ LED search method
1) Scan through , and at each point, reminimise L w.r.t nSM and nBG.
2) Plot L
3) 95 % C.L. result is the value of such that 95 % of area under the likelihood function lies between it and 0.
L = 1 e – ADD Equation! Page 15 cdf 5892
2SM2
nLED() is the fitted number of events attributable to LED physics
3 parameter unbinned likelihood function: nSM, nBG =/MS4
Bayesian gaussian prior on nSM events
Bayesian gaussian prior on nBG events
Poisson constraint on total number of events
Term to weight events according to its consistency with the SM, SM-LED interference, direct KK shapes, and BG shapes
CDF 5892,5373
Tracey Pratt Durham Exotics Workshop
Tevatron
Tracey Pratt Durham Exotics Workshop
Dimuon acceptance
Tracey Pratt Durham Exotics Workshop
Diphoton constraints
hep-ph 0103055
200 220 240 260 280m0 (GeV)
K/MPl 0.1
0.08
0.06
0.04
0.02
s = 2 TeV
L = 2fb-1
Run II a, b
95 % C.L. m0 (GeV)
K/MPl 0.1
0.08
0.06
0.04
0.021000 1100 1200 1300 1400
s = 14 TeV
L = 100fb-1
95 % C.L.
m1 : 700-1150 GeV m1 : 3.5-5.5 TeV
Tevatron LHC
||<1.2 for both ||<2.5 for both Using (KLED=1.3) for full