# Presentation: 477202

## 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

- Extra Dimension

- March 2003

## Extra dimensional solutions to the hierarchy problem (MEW << MPlanck?) 

- 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

- compactified

- for n  2, Rc < 1 mm

- Vn = 2Rcn

- MPl(4+n) ~ 1 TeV

- MPl2 = VnMPl(4+n)(2+n)

-  requires Rc ~ 10(30/n –19) m

*To solve hierarchy*
*        **choose*

- Torus

- ADD

- RS

## Searching for            ED

- Two classes of experimental tests
- Graviton emission
- 		and a photon or a jet recoiling against it,
- 		Gravitons, do not interact with the detector, and radiate into the bulk appearing as missing energy:
- 	jet + ET		 + ET
- Cross section depends on the number of extra dimensions
- 2.   Graviton exchange
-    	 Deviations in the cross section from SM predictions

- _New Parameters_
- String scale Ms = MPl(4+n)
- A factor  (=1) Hewett

- 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

**1)** **Direct G****KK ****emission** in association with a vector-boson :
-     	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

- the collider signatures include single photons/Z/jets with missing ET or fermion/vector boson pair production

- ADD

- probe Kaluza-Klein gravitons (GKK) by:

- Picture of cross-section for emission

- 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

- hep-ph/9904234

- s is the Planck scale in the extra dimensions
-  is a dimensionless parameter of order  1

- =+1

## Searching for         ED

- RS

- (Add BRs here?!)

- (Why not diphoton ?!!)

- K/MPl

- 6

- 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)

- Massive eigenstates only suppressed by -1 ~ TeV-1
- RS modes can be excited individually on resonance

- Via Virtual exchange
-         but different expected cross sections/distributions from ADD model

**Via virtual exchange**

- hep-ph0006041

-      1000     3000     5000

- 1
- 0.5
- 0.1
- 0.05
- 0.01

- 1
- 0.7
- 0.5
- 0.3
- 0.2
- 0.1

- 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

-  LHC

## Tevatron pp collider 

- CDF

- Run 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

- 20 x more events

- Physics reach extended

- 8

- and ability to set improved limits on new physics

## CDF at the Tevatron

_*CDF detector is essentially new, commissioned and now taking physics-quality data!*_

- Improved sensitivity for leptons and photons

- _Highlights of Upgrade_
- Improved trigger
- Improved silicon tracker
- Improved central outer tracker
- New forward calorimeters
- Extended muon coverage
- Time of flight detector

- Run I

- Run II

***Taking physics quality data since February 2002***

## CDF ED Searches

*Emission Channels*
- 	  + MET , jet+ MET
*Exchange*
- Diphoton, Dielectron and combined

- ADD

- RS

- Dimuon
- Dielectron

- (top pair,

## Run I GKK emission: Et

- Run I GKK emission: Et

- Events surviving cuts
- 15,046
- 1,475
- 94
- 11

- CDF 5725

**Limits**
- n=4  MS > 0.55 TeV
- n=6  MS > 0.58 TeV
- n=8  MS > 0.60 TeV

- The fundamental mass scale MD and R are related to Newton’s constant GN-1  and the number of extra dimensions by GN-1 = 8RnM2+nD

- No signal is observed

- L3 has set limit MS >1 TeV for n=2 (hep-ph0003306)

**Search Selection**
-  - One  with ET > 55 GeV and ||<1
-  - Missing ET > 45 GeV
-  - No jets with ET > 15 GeV
-  - No tracks with pT > 5 GeV

**Main backgrounds**
- Cosmic rays where muon undergoes a Bremsstrahlung in the calorimeter
- Irreducible Z +
- We (), W (),  (),jet-jet, -jet (+MEt)

**Results**
- Expected background: 11  2 events.
- Observed: 	        11 events.

- irreducible

- 95 % C.L. ADD limits:
- GN-1 = 8RnM2+nD
- MD = 549, 581, 602 GeV
- 	n=4,6,8 extra dimensions

**but no track is found**

- Other backgrounds:
- W->e nu, where the e is misidentified as a photon
- W -> where the charged lepton in a leptonic W decay is lost
- Prompt photon-photon production where a photon is lost
- Dijet
- Photon+jet production

- CR cuts are timing cuts
- (No jets with ET > 15 GeV and No tracks with pT > 5 GeV) are to remove backgds from W and events in which mismeasurement of jet energy produces fake MEt

## Real GKK emission : jets+Et

- CDF 5151

- Dashed lines for  from Pythia
- Solid lines prediction from Giudice, Rattazi and Wells (hep-ph9811291)

-  falls as 1/MSn+2 for all subprocesses

- qq-bar  gG is larger for larger values of n, relative to the other sub-processes,
- since (gggG) and (qggG)
- depend on (m2/s)4
- Whereas (qq-bargG)  depends on (m2/s)3
- This results in larger splittings at high values of MD between values of n for qg and gggG compared to qq-bargG.

- For n=2 qq-bar is not the dominate process, but for n>2 then this is the dominate process

| Process
MS = 1 TeV | n(pb)
Total) | n(pb)
Total) | n(pb)
Total) |
| --- | --- | --- | --- |
| qq-bargGKK | 4.1 
(0.16) | 1.6
(0.53) | 0.70
(0.78) |
| qggGKK | 9.6
(0.38) | 0.68
(0.22) | 0.096
(0.11) |
| qggGKK | 11.4
(0.45) | 0.77
(0.25) | 0.11
(0.12) |
| Total | 25.2 | 3.05 | 0.90 |

- Tevatron s=2 TeV MS = 1.2 TeV

- n=4

- n=2

- pTmin (GeV)

## Run Ib GKK emission: jets+ET

- CDF 5151

- The fundamental mass scale MD and R are related to Newton’s constant GN-1  and the number of extra dimensions by GN-1 = 8RnM2+nD

- Main backgrounds ? Talk about/consider?
- Dominate sources of uncertainty?

- Compare to LEP and Delphi results?- in the paper (for that time)

**Search Selection**
-     Jet ET1st 80 GeV, || <1.1 and ET>80 GeV
-     a second jet is allowed if ET2nd > 30 GeV
-     no isolated tracks in event (pT10 GeV)
**Main background** Z()+jets, W()+jets.

- L3 gives limit Ms > 600 GeV hepph0003306

- pp  jet +MEt subprocesses:
- qggG, qq-bargG and gggG.
- Main bkgd from Z+jet +jet
- LHC: qggG gives largest contribution

|  | MS (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

**Results**
- Expected: 27416  Observed: 284 events.
- Relative uncertainty on the signal acceptance 25 %

**Limits**
- 95 % C.L. upper limit on number of signal events: 62

- 84  4 pb-1

- Used Poilim (poisson statistics) 

- Normalise bkgd predictions to Zee+jets data and use direct normalisation of W->enu+jets as a cross check

- Allowing a 2nd jet: improves the signal eff. (2nd jet from ISR or FSR) And allows us to estimate the QCD bkgd using data.
- No tracks; reduces bkgd from W+jets

## Predicted results for GKK emissionjet+ET 

| n | CDF Run I results | MS reach
Run I         (GeV) | MS reach
Run II >300pb-1 (GeV) | MS 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.

- and requiring signal significance S/B = 5, assuming bkgd cross-section known to within 10 % and requiring that the signal be more than 50 % of the background to have confidence of a discovery.

- PRL **82**,2236 (1999)

- G. Giudice, R. Rattazzi, J. Wells

- |jet|<1.1 and EminT, jet = 80 GeV

- LHC with 300 times more data

## Virtual Graviton Exchange

- Clean experimental signature. Low backgrounds

- Diphoton Channel

- gg initiated process

- +

- Standard Model

- Extra Dimensions

- +

- Interference term of gg-> between SM and KK is not in their gamgam searches in Run I, they take this a a systematic uncert, however , intereference of qq-bar term is in the MC and qq interference term about 0.1* qq-bar interference term (CDF5694)

- Dilepton Channel

- qq-bar and gg ->  : gg process contributes about 30 % of the cross-section

## Fit method used

- (Comment on ang distrib too )

- s is the Planck scale in the extra dimensions
-  is a dimensionless parameter of order  1

- CDF 5892,5373

- KLED=1.3

- and to date (March 2002) has not been theoretically estimated.

- Cross section has form in :

- A 3 parameter (nSM, nBG, ) unbinned likelihood function is used to extract 

- MC templates for each piece can be generated that are independent of the choice of  and s4.

- 103
- 102
- 101
- 1

- 0   200  400  600  800  1000 1200

- M (GeV/c2)

- events

- Parameterise 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 events
**Limits**
-           Using a maximum likelihood fit method

- CDF: M > 150 GeV 5 events are observed where 4.5 +/-0.6 were expected with luminosity 100 pb-1 , and a limit MS > 0.9 TeV for n=4 was obtained. (hepph0003306)

- CDF5694

- MC distribution for the excluded signal shown here too

- CC 100 pb-1, CP 87 pb-1

- Plug

- Central

- 2 separate analyses – CP and CC –
- 	 then combined to give:

- Problems gg interference –

- 95 % C.L. MS > 797 / 899 GeV KLED = 1.0
- 	     ( = +1/-1, Hewett)

- Mhighest = 288 GeV/c2

- Background falls off faster than signal.
- In CC above 200 GeV:
- Expect less than 0.2 events, as opposed to 2.5 SM  events

## CDF Run I ee search for LED

- 2 high Et isolated electrons (> 25 GeV) (CC and CP)

- ee and  CDF results cdf 5753
- 95 % C.L. MS > 826 / 905 GeV ( = +1/-1, Hewett) KLED = 1.0
- 95 % C.L. MS > 853 / 939 GeV ( = +1/-1, Hewett) KLED = 1.3

- KLED applies to the LED terms of the cross section, and to date (March 2002) has not been theoretically estimated. Therefore quote a SM-like K-factor result and also one where no loop corrections are assumed.

- 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

- 2 separate analyses – CP and CC – then combined to give:

- Highest energy event is 500 GeV

- 110 7 pb-1

- NSMCP = 3883  292 (DY)
- NBGCP = 224  71
- Observed 3825

- Main Backgrounds: Drell-Yan, QCD di-jet, diboson production, Z,tt-bar production

- CDF 5892

- NSMCC = 3463  223 (DY)

- 500 GeV

- CC: 3319

- CP: 3825

## CDF  + ee search for LED

- Combine the likelihoods  (cdf5753)
- (Acounting for correlated and uncorrelated uncertainties)

| 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.

- CDF5753

- 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.

- as advocated by Cheung and Landsberg)

##            Run II GKK exchange reaches

- 2 fb-1 Run II dilepton data
- (hep-ph 0006041)

- Increased sensitivity to ADD model since can study angular distribution with more statistics

- Compare to LEP?
- Add Z’ table numbers

- _ADD model_
- Run I (110 pb-1) ee +    Ms 1.0-1.4 TeV for n=7-2
- corresponds to R < 0.3 mm (n-2) and R < 2 fm (n=7)
- Run II (2 fb-1)	            Ms 1.3-2.5 TeV for n=7-2
*n = number of extra dimensions*

- HLZ notation: hep-ex 0008065 D0 results: ADD
- Corresponds to R < 0.3 mm (n-2) and R < 2 fm (n=7)

- hep-ex 0008065

| Run I, 0.13 fb-1 | Run IIa, 2 fb-1 | Run IIb, 20 fb-1 | LHC, 100 fb-1 |
| --- | --- | --- | --- |
| 1.3   TeV | 1.9  TeV | 2.6  TeV | 9.9  TeV |

- 95 % C.L. sensitivity limits on Ms (n=4), from , ee,  channels
- Using double differential cross-sections

- hep-ph 0003306

| Run I, 0.13 fb-1 | Run IIa, 2 fb-1 | Run IIb, 20 fb-1 | LHC, 100 fb-1 |
| --- | --- | --- | --- |
| 0.13 fb-1 | 2 | 20 | 100 |
| 1.3   TeV | 1.9 | 2.6 | 9.9 |

- 95 % C.L. sensitivity limits on Ms
- Using double differential cross-sections

- n=4

**e****+****e****-**** + ********+********-**** + ******

- ADD

## CDF ED Searches

*Emission Channels*
- 	  + MET , jet+ MET
*Exchange*
- Diphoton, Dielectron and combined

- ADD

- RS

- Dimuon
- Dielectron

- (top pair,

##  Initial Run II         limits: ee,  

- MZ‘ > 275 GeV/c2

- 16 pb-1
- No deviations from the SM observed
- Limits set on one Z’ and RS model

- Run 2 ****

**Graviton mass (GeV/c****2****)**

- pb-1

- initial results

- Now updated

- RS

- CDF6080,6073

##         limits  72 pb-1

- RS

**Search selection**
- 	2 isolated  PT>20 GeV/c, ||<1
- 	Cosmic ray rejection cuts
**Results**
- 	Observed 775** **events
- Signal region above 150 GeV/c2 observed 4 events
**Limits**
- 95 % C.L. upper limit on number of signal events: 5.6

- K=1.3

- 208 GeV/c2

- CDF6344

## Run II cosmic ray rejectionusing the Time-of-Flight detector

- 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

-    Tupper

- Tlower

## Run II         ee search 72 pb-1

- 371 GeV

- RS

**Search selection**
- 	2 isolated e (CC, CP)
- 	ET>25 GeV
**Results**
- 	Observed: 4576 ee events
- Above 200 GeV/c2 observed 27, expected 16  8
- Above 350 GeV/c2 observed 3, expected 1.1  0.3

- CDF6344

## Run II         ee search 72 pb-1

- 95 % C.L. Excluded region
- K=1.3

- 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

- RS

- 20 % rather than 50%
- Total acceptance
- Effic: for
- ee CC:84% CP:69%
- Mm: PP= 57%, XX 65%, PX 61%

- CDF6344

##          constraints 

- (hep-ph 0006041)

**Tevatron ****2 fb****-1**

- 250   500   750  1000 1250

- Oblique Parameters

- m1 (GeV)

- ee+****** **2fb-1

- Dijet

-          constraints

- 0.01

- 0.50

- 1.0

- 0.20

- 0.02

- 0.05

- 0.10

- Excluded Region

- |R5| < M52

**LHC**

- RS

- Allowed Region

##          constraints

- hep-ph/9909255

- _e__+__e__-_

- _Hadron_
- _colliders_

- RS

## Outstanding Questions

- K factor:
- 	ADD CDF ee+  use KLED = 1.0 and 1.3
- “They place a KLED on the LED terms of the production cross-section: 1.0 for no loop corrections and a SM-like 1.3 for two independent cases.” (cdf 5753)
- used to correct the LO cross-section to NLO:

- What should the k-factor used for ED searches be?
- 	1.0 as for no loop corrections ?
- 	or 1.3 like in the SM ?
- Is ADD model in Pythia ?

**?**

**?**

- Should K=1.3 apply to the non-QCD process of graviton exchange?

## Conclusions and outlook

-  Searches performed in several channels at CDF
-  No evidence of deviations from Standard Model expectation observed
-  Best limits obtained are
- 	 ADD ee +     939 (853)  GeV for =-1 (+1), KLED = 1.3
- 	 ADD jets+ET    995 for n=2, 768 for n=4
-         RS   ee            205 to 535 GeV for k/MPl 0.025 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 II has a promising observation potential  	              	and should be in a position to discover ED, if they exist,
- ADD: up to about MS = 2 to 3 TeV (Runs IIa, 2 fb-1; IIb, 20 fb-1)
-       RS: m1 from 0.5 to 1 TeV for k/MPl 0.01 to 0.1 (Run IIa, 2 fb-1)

- The highest limits obtained are from the ** channel.

-  Many interesting channels to look in.
-  Run II results already coming in
-  To be updated in the future...

## THE END!

## CDF Run II          model searches

-  Determine signal regions
-  Obtain expected background in the signal region
*See an excess? **	**	*
*If no excess is observed*   obtain an upper limit on the number of 			  	 expected events (N95%):
- 			Using the number of observed dimuons and
- 	 	              expected background in the signal region
- 		              and their uncertainties
-  Find cross section limit (95%) limit from N95% :
- 	efficiency ()
- 	acceptance A(M)
- 	luminosity (L)

- 95%.BR(Z’/G ) =      N95%_ _
- 		          A(M) L

*To set a limit if no excess is observed*

- Recipe
- Ingredients

-  Lower mass limit (M95%)

- RS

## Tevatron

## CDF ll/ LED search method

- ee and  CDF results cdf 5753
- 95 % C.L. MS > 826 / 905 GeV ( = +1/-1, Hewett) KLED = 1.0
- 95 % C.L. MS > 853 / 939 GeV ( = +1/-1, Hewett) KLED = 1.3

- 110 pb-1+/- 7 Run I
- NSMCC = 3463  223
- NSMCP = 3883  292
- NBGCP = 224  71
- The CC BG is negligible.
- Observed:
- CC: 3319, CP: 3825

- 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
-        2SM2

- 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