# Presentation: 513340

## Search for New Physics with Photons at the Tevatron

*Shin-Shan Yu*
*Fermi National Accelerator Laboratory*
*for the CDF and D0 collaborations*

*2007 Europhysics Conference **on High Energy Physics,*
*Manchester, England** *

## Outline

- Motivations
- Tevatron and detectors
- How to suppress photon background
- Model-inspired search
- Target for one particular model and optimize for sensitivity
- Compositeness e*eee
- GMSB SUSY MET
- Signature-based search
- Driven by the Run I eeMET  event and MET excess
- MET
- e, 
- 
- e/ +  + X, X = MET, , or e/
- Conclusion

- Shin-Shan Yu

- July 19th, 2007

## Theoretical Motivation

- SUSY
- mSUGRA: 0201
-  bcMET, eeMET, MET, MET ....
- GMSB (Gauge-Mediated Supersymmetry Breaking): 01G
-  ****** ****MET**, bbMET, eeMET, MET, **displaced ********X** ...
- Compositeness: X* X
**ee******, 
- LED Graviton: MET, ****
- Higgs: eee****...
- Technicolor
- T  T
- bb,  jj,  tt,  ...
- 4th Generation
- b'  b
-  bbeebb, bb, jjbb

- See Per Jonsson’s talk

- See Smain Kermiche’s talk

- See Max Goncharov’s talk

**This talk**

- Shin-Shan Yu

- July 19th, 2007

## Experimental Motivation

- CDF Run I ee+MET event
- 86 pb-1
- Dominant SM from WW:
- 810-7 events
- Total Bg: 10-6 events
***PRL 81, 1791 (1998)***
- CDF Run I +MET excess
- 86 pb-1
- 11 observed
- 4.2 ± 0.5 expected
***PRL 89, 041802 (2002)***
- Motivate signature-based searches of +X and l +X at Run II
- MET
- e, 
- 
- e/ +  + X, X = MET, , or e/

- A hint of new physics?

- Shin-Shan Yu

- July 19th, 2007

## Tevatron Performance

- CDF and D0 have > 2.5 fb-1 of data on tape (3 fb-1 delivered)
- Record initial luminosity: 2.9×1032 cm-2s-1
- Expect 4-8 fb-1 by 2009
- Will focus on ~1 fb-1 results in this talk

- Int lumi in this talk

- sqrt(s) = 1.96 TeV

- Shin-Shan Yu

- July 19th, 2007

## Detectors

- : shower in the EM calorimeter with no associated track
- Multi-purpose detector: tracking chamber, EM (ECAL) and Had calorimeters (HCAL), and muon chamber

- Measure EM transverse shower profile at shower maximum

- Shin-Shan Yu

- July 19th, 2007

## How to Suppress Photon Backgrounds 

- Photons not produced in hard scattering process
- 0, Ks, and in jets
- Most of the energy deposited in the EM calorimeter
- Require isolated photons
- EM shower profile consistent with single photon.
- Electron bremsstrahlung or tracking inefficiency
- Road from the EM cluster to the event vertex
- Search for hits along the road
- Reduces electron by a factor of 3 to 7

- Shin-Shan Yu

- July 19th, 2007

## Search for Excited Electrons e*e 

- Possible sign of compositeness
- m(f*) and compositeness scale 
- Look in Contact Interaction channel qq→ee*→ee
- Single EM or di-EM triggers
- 2 isolated electrons (ET1 > 25 GeV, ET1 > 15 GeV), 1 isolated photon (ET > 15 GeV), |det|  < 1.1 or 1.5 < |det|  < 2.5
- ee control sample
- Dominant bg: Z
- Pythia MC and corrected to NNLO cross-section (Hamberg, van Neerven, Matsuura)

- Shin-Shan Yu

- July 19th, 2007

## Search for Excited Electrons e* 

- Optimize minimum requirement on m(e)
- Use second leading electron for m(e*) ≤ 200 GeV
- Use electron which give m(e) closer to the search regon for m(e*) > 200 GeV
- For m(e*) < 300 GeV, optimize cuts on the R(e2,)
- No excess, 95% CL limit  for compositeness scale = 1 TeV,  m(e*)> 756 GeV

**For********= 1 TeV,  m****e***** > 756 GeV**
**For******** = m****e*****,  m****e***** > 796 GeV**

- Shin-Shan Yu

- July 19th, 2007

## Search for GMSB SUSY in MET

- SUSY breaking mediated by gauge interactions
- LSP is gravitino
- Snowmass Slope SPS 8 model
- Single parameter  determines the effective scale of SUSY breaking
- Single-EM trigger
- Require two isolated central photons with ET > 25 GeV
- Photon vertex consistent with primary:  = (95.8±0.1)%
- Photon vertex: line along pre-shower detector and 4 layers of ECAL,  = 2.3 ±0.3 cm

- Expected MET from GMSB

- MET
- Jets: midcone, size 0.5
- Uses CAL || < 4.0
-  (leading jet, MET) < 2.5 radians

- Shin-Shan Yu

- July 19th, 2007

## Search for GMSB SUSY in MET

- Search for GMSB SUSY in MET

- Backgrounds
- Fake MET from jets: MET shapes from Z->ee and multi-jet samples, normalized to the low MET region in the sample
- Real MET from W, Wj: apply e-> rate rate (~1.4%) to the MET in e events
- Z, W: CompHep MC (x-check with Madgraph)
- No excess, use binned MET distributions to set 95% CL limit:
-  > 88.5 TeV, m10 > 120 GeV, m1+ > 220 GeV

**1.1 fb****-1**

- Fake
- MET

- D0 Run II Preliminary

- D0 Run II Preliminary

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous MET Events

- Search for Anomalous MET Events

- Diphoton trigger
- Central photons with Et > 13 GeV
- All backgrounds estimated from data
- Fake MET
- parameterize fake MET
- dijet sample for jet energy resolution
- 0-jet  events in loose photon and Z->ee samples for UE and MI
- Real MET
- Apply e-> rate (0.4-2%) to eevents
- Beam Halo, Cosmic
- Remove photons with beam halo topology
- Require EM timing consistent with collision time or remove photons close to trackless muon hits
- Extrapolate from out of time events

-  For MET > 50 GeV. 4 observed, 1.6 ± 0.3 expected

- See Max Goncharov’s talk

**1.2 fb****-1**

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous e, Events

- Diphoton trigger
- 2 central photons with Et > 13 GeV and 1 lepton Et > 20 GeV
*W***and Z (MadGraph)

- Ht = scalar sum of Et from photons, leptons, jets, and MET

**1.1 fb****-1**

| e | 6.82±0.75 | 3 |
| --- | --- | --- |
|  | 0.79±0.11 | 0 |

-  A denominator times fake rate for:
-  jets faking leptons:  jet
-  jets faking photons: W(Z)+jet, W(Z)+2jets
-  electrons faking photons: Z, Z+jet

- Dominant Bg

- Z

- Z

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous  Events

- Search for Anomalous  Events

**1.2 fb****-1**

- Diphoton trigger
- 3 central photons with Et > 13 GeV
- SM tri-photon production estimated from Madgraph with K-factor 1.5±0.2

| SM tri-photon | 0.80 ±  0.15 |
| --- | --- |
| Fake from jets | 1.4 ± 0.6 |
| Total | 2.2± 0.6 |
| Observed | 4 |

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous l X Events

- Motivated by the CDF I  MET excess
- Repeat the same kinematic requirements
- Inclusive lepton or photon triggers
- Basic objects:
- Central lepton (e,) > 25 GeV, central photon > 25 GeV
- X = MET, lepton, or photon
- MET > 25 GeV
- Photon > 25 GeV
- Loose central electron Et > 20 GeV, forward electron > 15 GeV, central muon Pt > 20 GeV

-  Background
-  W, Z, W, Z: Madgraph MC
-  Fake photons from electrons
-  Fake photons or leptons from jets:
- study isolation shapes in QCD events and golden leptons

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous l X Events

|  | Exp. | Obs. |
| --- | --- | --- |
| eMET | 94.8±8.1 | 96 |
| MET | 55.7±7.1 | 67 |
| ee | 39.0±4.8 | 53 |
|  | 26.1±3.1 | 21 |
| e | 0.53±0.13 | 0 |
|  | 0.10±0.06 | 0 |
| e | 1.0±0.3 | 0 |

**0.9 fb****-1**

- Shin-Shan Yu

- July 19th, 2007

## Conclusion

- Both CDF and D0 have performed extensive model-dependent and signature-based searches with photon final states
- No hint of new physics in 1 fb-1 of Run II data
- CDF I excess can not be confirmed.
- Improve analysis techniques
- Results from other photon final states and with 2-8 times more data will come out in the future
- , b, j and more
- Keep looking. Something unexpected before LHC?

- Shin-Shan Yu

- July 19th, 2007

## NP

## Backup Slides

## Control Sample of Search for e*

- Shin-Shan Yu

- July 19th, 2007

## Optimize Cuts for the Search of e*

- Shin-Shan Yu

- July 19th, 2007

## BR e* -> e when = 1 TeV

| (me*) | BR(e*->e) | S (NNLO) X BR (pb) |
| --- | --- | --- |
| 100 | 0.27 | 35 |
| 200 | 0.21 | 7.3 |
| 300 | 0.15 | 2.2 |
| 400 | 0.11 | 0.67 |
| 500 | 0.08 | 0.23 |
| 600 | 0.06 | 0.08 |
| 700 | 0.05 | 0.02 |
| 800 | 0.04 | 0.006 |
| 900 | 0.03 | 0.002 |
| 1000 | 0.03 | 0.0004 |

- Shin-Shan Yu

- July 19th, 2007

## Gauge-mediated interaction

- Shin-Shan Yu

- July 19th, 2007

## Search for GMSB in MET

- Basic Snowmass Slope SPS 8 Model
- Number of messenger = 1
- Messenger mass = 2 * 
- tan  = 15
- Sign of the Higgsino mass  > 0
- Hits on the road
- Recover electron efficiency from 93% to 98,6%
- Photon anti-track efficiency still 91%
- Require preshower hits from at least one of the photons
- E = 1-0.2*2 = 96%
- MET > 30 GeV, expected 9.8±1.1, observed 16 events
- MET > 60 GeV, expected 1.5±0.4, observed 3 events

- Shin-Shan Yu

- July 19th, 2007

## MET Distributions in the Control Sample of MET

- Shin-Shan Yu

- July 19th, 2007

## Electron Mis-identified as Photons

- Compare Z peak from ee and e
- Get Et dependence from MC
- Normalize to data
- Silicon-track rejections reduce the fake rate by a factor of 3-4

- 0.36% at 45 GeV

**Silicon track rejection applied**

- Shin-Shan Yu

- July 19th, 2007

## SM Production Cross-section

| Process | (pb) |
| --- | --- |
| WR | 27.20 |
| ZR | 6.86 |
| WR | 0.13 |
| ZR | 0.09 |
| Et>10 GeV,  < 1.2  | 0.008 |

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous e, Events

- Shin-Shan Yu

- July 19th, 2007

## Search for Anomalous l X Events

|  | Dominant Background |
| --- | --- |
| l MET | W |
| l l  | Z |
| e | Z |
|  | Fakes from jets |
| e | Z |

- Search for Anomalous l X Events

- Shin-Shan Yu

- July 19th, 2007

## The MET Kinematical Distributions 1

- Shin-Shan Yu

- July 19th, 2007

## The MET Kinematical Distributions 2

- Shin-Shan Yu

- July 19th, 2007

## The ee Kinematical Distributions 1

- Shin-Shan Yu

- July 19th, 2007

## The ee Kinematical Distributions 2

- Shin-Shan Yu

- July 19th, 2007