tracey pratt durham exotics workshop large searches at cdf, tevatron tracey pratt liverpool...

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


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


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)


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


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


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


CDF ED Searches

Emission Channels

+ MET , jet+ MET

Exchange

Diphoton,

Dielectron

and combined

Dimuon

Dielectron

and combined

(Diphoton)

(Dijet)

Run I

Run II


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


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


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


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


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


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

+

+

+


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


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


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


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.


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


CDF ED Searches

Emission Channels

+ MET , jet+ MET

Exchange

Diphoton,

Dielectron

and combined

Dimuon

Dielectron

and combined

(Diphoton)

(Dijet)

Run I

Run II


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


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


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


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


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


Run II ee + search 72 pb-1

95 % C.L. Excluded region K=1.3


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


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


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


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


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


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


THE END!


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


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


Tevatron


Dimuon acceptance


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

tracey pratt durham exotics workshop large searches at cdf, tevatron tracey pratt liverpool...

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