# Presentation: 063404

## Searches for Extra Dimensions and  Heavy di-lepton Resonances at D0

**Elizabeth Gallas**
-    Fermi National Accelerator Laboratory     Computing Division

**12th International Conference****on Supersymmetry****and Unification of Fundamental Interactions****June 17-23, 2004****Epochal Tsukuba, Tsukuba, Japan.**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
I am here to tell you about the new results from the D0 Experiment at the Tevatron
on searches for Extra Dimensions and heavy dilepton resonances

## Outline

- 3-Space / Time:
- Fermilab Tevatron with Experiment DØ / mid Run 2
- What can Extra Dimensions (ED) do for you ?
- Phenomenology (of interest for pp colliders)
- 2 particular ED models
**Large Extra Dimensions**
**ADD (Arkani-Hamed, Dimopoulos, Dvali)**
**TeV****-1**** ‘longitudinal’ Extra Dimensions **
**DDG (Dienes, Dudas, Gherghetta)**
- DØ: A window into ‘Extra Dimensions’ (ED)
- DØ: Lepton/Photon Final state searches for :
- Large Extra Dimensions (ED)
- TeV-1 ‘longitudinal’ Extra Dimensions
- Z’ boson
- Summary and Conclusions

**–**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
I am at at SUSY conference in a SUSY session
but I am not here to tell you anything necessarily about SUSY
except that SUSY is not the only possible extension to the SM to explain broader phenomena.
Some SUSY models include ED’s.

Our search for New Phenomena takes place at the Fermilab Tevatron.
and we look for it using the D0 experiment data.
I will descibe 2 Phenomenolgies which are sensitive to ED at Colliders
Large Extra Dimensions
‘small’ (TeV-1 longitudinal) Extra Dimensions 
Search Results

## TEVATRON Run 2 Upgrade

**TEVATRON Run 2 Upgrade**

**New Main Injector : 150 GeV**
**Store protons, shoot to target for anti-proton production**
**New recycler :**
**Magnet storage ring for anti-proton**
**Higher energy:**
**1.96 TeV vs 1.8 TeV**
**Higher cross sections **
**	****(30 % for the SUSY)**
**Higher antiproton intensity:**
**6x6 ******** 36x36 bunches**
**	****(3.5 μs ********  396 ns)**
**Higher luminosity**
**Run 1 : 2x10****31**** cm****-2****s****-1**
**Run 2 : 2x10****32**** cm****-2****s****-1**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
tev run 2 upgrade brought us many 
major improvements to accelerator operations that
result in higher E collisions (and thereby higher cross sections)
and a higher proton intensity.

The Tevatron has delivered now about 300 pb-1 to each experiment,
and the luminosity seen so far in 2004 already exceeds the total in 2003,

necessitated by The higher intensity and bunch crossing rate 
and combined with Run 1 experience and improved technology 
resulted in a number of improvements to the D0 experimental apparatus
for Run 2. 

Peak instantaneous luminosity now at 75E30

## DØ Run 2a Upgrade

**DØ Run 2a Upgrade**

**Solenoid (2T)**
**4-layer Silicon Vertex and 16-layer Fiber Trackers**
**Muon forward chamber (**||<2 **), shielding**
**New preshower, upgrade Calorimeter electronics**
**Upgrade to Trigger and DAQ system**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
DØ Run 2a Upgrade brought:
Solenoid (2T)
4-layer Silicon Vertex and 16-layer Fiber Trackers
Muon forward chamber (||<2 ), sheilding
New preshower, upgrade Calorimeter electronics
Upgrade to Trigger and DAQ system

## What can Extra Dimensions do for you ?

**...****proposals dating at least back to 1920’s...**
**Recent renaissance in the theory proposes:**
**unite all known forces (including gravity)**
**known particles, electroweak and strong interactions**
**confined to a ‘brane’ - a hypersurface in the “bulk” of 4+n Dim**
**gravity appears weak – diluted in extra dimensions.**

**There is no “desert”**
**Offers alternative to the “hierarchy problem”**
**only one important scale in nature --  may be accessible                                      **_**at Tevatron and LHC energies**_
**Lends practical aspects to string theory...**
**it’s not just a beautiful idea... we can test it !**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
Theories of ED’s have been around dating back to the 1920’s

‘brane’ named in analogy to ‘membrane’ in 2D

highest energy particle accelerators extend our range of sight to include
 the weak and strong forces down to small scales, around 10-15 mm 
(strong, weak and EM forces consistent down to that scale)

direct tests of gravity down to 0.2mm
we don’t see ED’s because they are ‘compact’ (much smaller than size of atom)

Randall and Sundrum: unification scale 1TeV

only way to probe ED is with gravitons themselves

hierarchy problem—the great disparity between the energy at which the weak and electromagnetic forces fuse together (102 GeV) and that at which gravity joins up with the other forces (1018 GeV). 

all this lends some practical aspects to string theory...
that experimentalists hadn’t previously appreciated (without these refinements)

Because the graviton moves off into the extra dimensions, we call it a Kaluza-Klein particle. 

## Large Extra Dimensions (LED)in the ADD Model

- Large Extra Dimensions (LED)in the ADD Model

**ADD (Arkani-Hamed, Dimopoulos, Dvali) model assumes:**
**n Extra Dimensions of size R**
**SM particles and interactions are confined to 4D-world (brane)**
**Gravity propagates in 4+n Dimensional space**
**Gravity appears weak – diluted in extra dimensions**
**In this formulation:**
**where M****Pl**** (**_**apparent**_** 4D Planck Scale):**
**Ms (**_**fundamental**_** Planck Scale) is brought                                             to the TeV range**
**Constraints (cosmology, tabletop expts):**
**Extra dimensions ‘compactified’ (R****C**** < 1 mm)**
**require n>1 (g forces at large distances)**
**Collider experiments – only probe for ED for n********3 !**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
I ask you to consider the possibility that physical dimensions exist --
dimensions that are in addition to 

Constraints (tabletop experiments and astrophysical observations) dictate that :
Extra dimensions compactified (Rc < 1 mm) – resolution of tabletop experiments
require nextra>1 (gravitational  forces at large distances)

## LED Tevatron Search Modes

**Direct Searches (graviton escapes the brane)**
**	****look for JET recoiling against missing ET (next talk)**
**Indirect Searches (this talk)**
**virtual graviton - contributions to ****l****+****l****-****,**** ********  production**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
KK gravitons are actually a tower of many graviton states
for both direct and indirect searches.

## Virtual Graviton Exchange

- The predicted cross section is described by:
**	**
**	****where ********g**** = F/M****S****4**** == (****in TeV****-4****) **
**	****describes strength of gravity in the presence of LED**
**	****and F is a dimensionless parameter ~ 1 which depends on the formalism (for the effective Lagrangian):**
**GRW:     F = 1**
**HLZ:       F = log(M****s****2****/M****2****), n =2**
**               ****F = 2/(n-2), n > 2**
**Hewett   F = 2********/********, ********=****±1**
- Experimentally, the process is defined by the
**invariant mass of the di-boson or di-leptons  (M)**
**cosine of the scattering angle, ********* (****|****cos *************|****).**

***SM term***
***interference term***
***direct gravity term***

- E. Gallas - SUSY 2004

- June_2004

## Search for ED in ee/ channel

- Dataset 200 pb-1
- Use di-EM objects
**both ee and ******
- Selections
- Two EM with Et > 25 GeV with tight quality cuts
- Fiducial requirements:
**central EM objects:**
**|eta| < 1.1 **
**central/forward objects:**
**1.5 < |eta| < 2.4**

**Bkg**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
“Effective” Luminosity:
 folding in acceptance, efficiencies and NLO cross section obtained by normalization to Z peak for same triggers

## Highest mass Drell-Yan event

- Invariant mass 475 GeV/c2, cos θ* = 0.01

- E. Gallas - SUSY 2004

- June_2004

## di-EM Mass,Cos θ* distributions

**di-EM Mass,Cos θ* distributions**

- E. Gallas - SUSY 2004

- June_2004

## Uncertainties:

- Uncertainties in G for di-EM sample

- E. Gallas - SUSY 2004

- June_2004

## LED: 

- MS > 880 GeV (95% CL)
- Run 2 Preliminary

- Luminosity = 100 pb-1
- Select events with
- 2 muons
- PT> 15 GeV
- M > 50 GeV

- E. Gallas - SUSY 2004

- June_2004

## Summary: Limits on LED MS for various formalisms F

**No evidence for signatures in excess of high-mass dielectron, diphoton or dimuon events over SM expectation, from coupling to Kaluza-Klein gravitons**
**Fit (di-EM Mass,Cos θ*) distribution  **
**Single parameter for ED effects: ****η****G**** = F/M****4****S  **
**Translate ****η****G**** limits to 95% CL lower limits on Planck scale M****S**** , in TeV, using different formalisms for F**
**DiEM limits  - combine Run I & Run 2 – best limits on LED to date**
**Di******** limits for Run 2 with more statistics -- in preparation**

- E. Gallas - SUSY 2004

- June_2004

## Dedicated ee Search for ‘longitudinal’ Extra Dimensions

- Another ED model (TeV-1 “longitudinal” EDs):
**proposed by Dienes, Dudas, and Gherghetta (DDG)**
**Fermions confined to 4D **
**but SM gauge bosons propagate in TeV****-1**** ED of size:**
**R = 1/M****C**** **
**Predicts Kaluza-Klein states of gauge bosons (********KK****, W****KK, ****Z****KK, ****g****KK****)**
**produced directly (with sufficient energy)**
**produced indirectly (virtual exchange of KK modes)**
- Lepton pair production cross section depends on
******C**** = ********2**** / 3 M****C****2**, where **M****C** = ‘compactification’ scale of TeV-1 ED
- This analysis:
**look for virtual exchanges of KK excitations of the Z and ******

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
complementary to the previous model is another model for EDs
which proposes that

## Dedicated ee Search for TeV-1 Dimensions (DDG)

- Dedicated ee Search for TeV-1 Dimensions (DDG)

**Predicts strong negative interference effects **
**unlike LED discussed before**
**Use di-EM dataset (****200 pb****-1****)**
**adding track match**
**fiducial requirements –      same as for LED analysis**
**Find upper limit on**
**	**** ********C**** < 2.63 TeV**
**	****and thereby (lower limit):**
**	**_**M**__**c**__** > 1.12 TeV (95% CL)**_
**First search of this type**

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
complementary to the previous model is another model for EDs
which proposes that

## Z Limits from ee: SM, E6

- Z Limits from ee: SM, E6

**Various models propose new neutral gauge bosons**
**SM couplings**
**variety of E****6**** GUT inspired**
**Dataset 200 pb****-1 ****– same as in ED analysis**
**Limits on Z’ mass in GeV/c****2****:**
- SM couplings
- 		Run I      Run II
- 	        670         780
- E6 couplings
- 		ZI    Zχ    Zψ   Zη
-         575  640   650  680

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
Caveat: DØ: K(MZ), K= 1.19-1.46
	actually, using NNLO + M-dependent K factor.  Mass dependence increases limit by perhaps 5 GeV
CDF: K = 1.30, but wrt different LO X section

## Z’: 

- No evidence: Set limits
- M(Z’) > 610 GeV
- Run 2 Preliminary

- This is a previous result under revision with increased statistics:
- We used the same dimuon sample as used for LED **** search to look for heavy Z-like resonances

- E. Gallas - SUSY 2004

- June_2004

## Summary

**No signal for new physics observed so far**
**but some interesting events !**
**New Limits from DØ: Extra Dimensions and Z’**
-                                          *  limits under revision with increased statistics
**improved limits on additional gauge bosons !**
**most sensitive collider search for ED’s to date!**
**higher efficiency in widest acceptance**
**di-EM channels using 200 pb****-1**** integrated luminosity (now 300 pb****-1**** on tape)**
**first collider search for TeV****-1**** ‘longitudinal’ Extra Dimensions**

| Topic | Prelim. Run 2 |
| --- | --- |
| LED : ee and  | MS >1.43 TeV (Run 1&2) |
| LED :  | MS > 880 GeV * |
| TeV-1 ‘longitudinal’ ED: ee | Mc > 1.12 TeV |
| Z’ :  | M(Z’) > 610 GeV * |
| Z’ : ee | M(Z’) > 780 GeV |

- E. Gallas - SUSY 2004

- June_2004

**Notes:**
D0 has new limits on Extra Dimensions and heavy new gauge bosons

These limits represent the most sensitive collider search for ED’s to date!
widest acceptance, hi
using more integrated luminosity