# Presentation: 848878

## SUSY Searches with Photons in CDF 

**Sung-Won Lee**
**CDF Collaboration/Texas A&M Univ.**

## Outline

**Physics Motivations ; Why Photon in SUSY...**
**    **_**SUSY and New **__**physics with photon final states**_
**Measurement of Photons in CDF II**
**New Particle Search Strategies at CDF II**
**CDF Exotics Searches with Photons in Run II**
-  **Conclusions and Outlook**

## The Interesting Event on the Tail

_**Prologue**_
_** **__**On April 28, 1995, CDF recorded a spectacular **__***ee***__****__***+***__**        candidate event.**_
** ****It is unusual because isolate**
**   ****leptons/photons, and especially**
**   ****large        are rare in the Standard**
**   ****Model.**
** ****Total *****“a posteriori”***** expected**
**   ****rate is 10****-6****, including possibly**
**   ****misidentified particles.**
** **_**CDF recently reported an excess**_
_**of events in **__******__****__**+**__**       channel that**_
_**disagree with SM prediction**_** ****(~2.7**
**standard deviation for Gaussian**
**distribution)**

_**What is it?, Statistical fluctuation?**_
_**or Hints of New Physics?**__** **_
**Lots of discussion between theoretical and experimental communities**
****** ****many theoretical interpretations...**

## More Interesting Event on the Tail

**CDF has performed a **_**model independent search**_** in Run I for new physics that gives leptons, photons, missing E****T**** in final state**
**Inspired by *****ee**********+*****        ****candidate event**

**The SM prediction yields the observed rate of a lepton+photon (+Missing Et) with 0.7% probability **_**(~2.7 standard deviation for Gaussian distribution)**_** **

**Recent theoretical explanation of the **************events is...******
_**“**__**Resonant smuon production with a single dominant R-parity violating coupling”**_**  ****(hep-ph/0111014)**

** **_**Search Selection:**_**   *****l(e******/************)*********events (Et>25 GeV)**
** **_**Main backgrounds**__:_** **
**   ****W/Z+********, lepton+fake ******_** **_

_**It’s an interesting result, but it’s **__**not a compelling observation**__** of new physics!!**_
**Run II analysis is**
** ****in progress now**

## We can search for new physics with photons in the final state
Why photon? 

**Why photon? **

**Photon Signatures of New Physics **

** **_**SUSY (N**__**2 **__****__** **__****__**N**__**1**__**, Light Gravitinos)**_
** ****Large Extra Dimensions **
** ****Composite Models (Excited Leptons)**
** ****Technicolour**
** ****Bosephilic Higgs: W/Z+Higgs ******** W/Z+******
** ****Anomalous W(****************)/Z(************, ********) + ******** production**

_**SUSY Models**_
** ****Minimal SUSY extension**
**   ****of  SM  ****(MSSM)**
** ****Minimal Super-Gravity**
**   ****(mSUGRA)**
** ****Gauge Mediated SUSY**
**   ****Breaking  ****(GMSB)**

**High P****T**** physics with photons and**** **

**The primary motivation for searching in photon final states is that the photon is likely to be **_**a good probe of new interactions**_**, particularly **_**SUSY**_**.**

_**Empirically interesting !!**_

## SUSY Photon Signatures at Tevatron

**In recent SUSY models, **_**two main choices of SUSY breaking have come**_
_**into favor that predict photons in the final state.**_** SUSY particles are not **
**degenerate with Standard Model particles ******** SUSY is broken either...**

** **
** ****Breaking transmitted to visible **
** ****particles by gravitino interaction**
**    ****LSP = 1****st****  lightest Neutralino**
** ****NLSP = 2****nd**** lightest Neutralino**
**             ********2****0**** ******** ********+ ********1****0**** **
** ****If ********1****0**** is mostly higgsino and ********2****0**** is **
** ****mostly gaugino**

- 

- 

- 

- 

**Supergravity**

**via ****Standard Model Gauge Interactions**

**via ****Gravity**
_**(Heavy Gravitino)**_

** **
** ****Gravitino mass, ****M****G ****, related to**
** ****SUSY breaking scale, ********F**
**    ****LSP = Gravitino**
** ****NLSP = Neutralino**
**             ********0**** ******** ********+ G**** **
**Relevant mass range:**
**                ****O(10****-2**** < ****M****G**** < 10****4****) eV**** **

**GMSB**

**The process will result in  ********       +X events if both neutralino decay inside the detector.**

- 

- 

## CDF II Detector @ Tevatron

-     _**Highlights of Upgrade**_
**  ****New front-end, DAQ and trigger**
**  ****New silicon vertex detector**
**  ****New central outer tracker**
**  ****New end-plug calorimeters**
**  ****Extended muon coverage**
**  ****New time-of-flight system**
**  ****EM calorimeter timing (Summer 03)**

**CDF II Detector @ Tevatron**

**CDF II detector is essentially new, commissioned and now taking physics-quality data @ 1.96 TeV since Feb 2002**

_**Major components used in CDF II Photon Physics **_
**1. Central EM Calorimeter System**
**2. Central Tracker **
**3. Timing from Hadron Calorimeter**

## 
Central Photon Cuts: 

Adjust transverse quantities to vertex
Number of 3-D track 
E fraction b/w HAD and EM Cal.
Calorimeter Isolation
Track Isolation
Two topological shower quantities
     1. EM Shower width
     2. EM Shower cluster energy

Additional Selections: 

reject cosmic-ray
reject Tevatron Beam-Halo events

_**Central Photon Cuts:**__** **_
**Adjust transverse quantities to vertex**
**Number of 3-D track **
**E fraction b/w HAD and EM Cal.**
**Calorimeter Isolation**
**Track Isolation**
**Two topological shower quantities**
**     ****1. EM Shower width**
**     ****2. EM Shower cluster energy**
_**Additional Selections: **_
**reject cosmic-ray**
**reject Tevatron Beam-Halo events**

_**Many Triggers: all are running,**_
_**including L2 (central/plug photons)**__** **_
**Inclusive Photon: Et>25, w/   ISO**
**Ultra(Super) Photon: Et>50(70)**
**Diphoton: Et>12, w/   ISO**
**Diphoton: Et>18, w/o ISO**
**Triphoton: Et>10, w/o ISO**
**Photon: Et>16 + Muon**
**Photon: Et>16 + 2 jets (W/Z+   )**
**Photon: Et>10 + SVT track**
**Large samples are being collected,**
**tested and many studies started:**
_**Backgrounds, calibration, fake rates,**_
_**simulation...**_** **

****

**Standard Photon ID**

**Triggers/Dataset**

## Identification of Photon Signals in CDF

_**Signals**_
_**Backgrounds**_

****

****

****

******0**

_**Photon candidates**_**:****  Isolated electromagnetic showers in the calorimeter, with no charged tracks pointing at the calorimeter cluster**

**  ****CDF uses two techniques for**
**   ****determination of photon signals;**
**   ****1. **_**EM Shower width (shape):**_
**       ****using Shower Max. Detector**
**   ****2. **_**Conversion Probability:**_
**       ****using pre-radiator  hits**
** ****For  every photon****, ****CDF find the **
**   ****fraction of candidates with these**
**   ****informations:**** **
**  ****(extracted signals statistically)**

**Identification of Photon Signals in CDF**

**Central Calorimeter**

**Shower Maximum Detector**

**Pre-shower Detector**

|  | - | -Jet | Jet-jet |
| --- | --- | --- | --- |
|  CPR | 29±23% | 40±28% | 30±23% |

**e.g.  for diphoton candidates,**
**S/B result using CPR method is..**

## New Particle Search Strategies at CDF II

_**1. Traditional Model-driven Analyses**_
**pick a favorite theoretical model & process, choose the best signature(s): optimize selection acceptance based on signal MC**
**calculate the expected backgrounds**
_**evaluate the limit or discover a new signal**_** **
_**2. Signature-based Approach**_
**pick a specific signature ****(e.g. diphoton+X)**
**define the sample in terms of known processes**
**publish estimates of acceptances & cross section information useful for theorists**
_**see an excess?  inconsistency with SM?  test one or more models later.**_** **

**Best optimization, but model might become some outdated..**

**Not best optimization but open to a whole lots of models;**
**An unbiased study is fundamental for data understanding.**

**Two different approaches for new particle search with photons will be actively pursued in CDF Run II experiment in a complementary way:**

## Exotics Searches with Photons 

**in CDF Run II**

** ****Search for ****Anomalous**** ****Di-Photon+****       Production**
** ****Search for ****Anomalous**** ****Photon****+Lepton**** Production**
** ****Search for ****GMSB**** with ****Di-Photon+**
** ****Search for ****LED**** with ****Photon+**
** ****Search for ****Excited Lepton**** with *****ee*****+****photon**
** ****Search for ****W/Z+****Photon**

## +X  Signature-based Searches

**Run I Search for an excess of events in the ********+*****X***** final state,**
**will generalize the Cousin Search to a full Signature Based Search**

_**where X is...**_
**  **_**Gauge Boson:**_
**     ****W, Z, gluon(******** jet) or**
**     ****extra photon**
**  **_**Quark:**_
**      ****Light quarks,  b-quarks,**
**      ****t-quarks (t********Wb)**
**  **_**Leptons:**_
**      ****Electrons, Muons, Taus, **
**      ****Neutrinos (Missing Et signature)**
**      ****Leptons from****  ****W****************, **
**                                   ****Z************,  Z******

**All results are consistent with the Standard Model background **
**expectations with one possible exception, *****ee**********+*****       event**

## Search for Anomalous  Events at CDF

** **_**Search Selection:**_** **
-      **2 central photons with Et>13(25)**
**     ****Cosmic and beam halo clean-up**
** **_**Main backgrounds**__:_
-     **fakes from photon-jet and jet-jet**
** **_**Results:**__ _**1365(95)events for Et>13(25)**** **

**M********=168GeV**

**        **_**For **__**M**__****__** > 150 GeV**_
**Expected background:   3.3  **
**Observed: ****	****              2.0**

**       **_**Run I Results (LED Search)**_
**observed: 287(192) CC(CP) events **
**                  **
**95% C.L. Limits on eff. string scale:**
**using a maximum likelihood fit method**

**NO excess observed @  High **
**invariant mass, **_**good agreement **_
_**b/w Run II Data and expectation**_

**        **_**For **__**M**__****__** > 150 GeV**_
**Expected background: 4.5 ******** 0.6  **
**Observed: ****	****             5**

**95 % C.L. M****S ****> 899 / 815 GeV**
** ****K****LED ****= 1.0  (******** = -1/+1, Hewett) **

## +Jets,  +Leptons Search at CDF

** **_**Search for **__****__** + X; X=jet(s)**_** **
**To search for anomalous production of quarks and gluons, look in anomalous N****jet**** production in ************data**

** **_**Search Selection:**_**  ****Diphoton+extra lepton(s)**
** **_**Main backgrounds**__:_** **
**   ****W/Z+********, fake ********, Z********,e(********)********+jet**_** **_

**P(e fake ********)**
**= 1%**

**No event is found**

**Good agreement b/w Run II data and expectation..**

**Result consistent with SM**

** **_**Search for **__****__** + X; X=lepton(s)**_** **

## Search GMSB for +      (I)

**                  **

** **_**Search Selection:**_** **
-      **2 central photons w/ Et>13(25)**
**     ****Cosmic/beam halo clean-up**
** **_**Main backgrounds**__:_ **(see plot)**_ _
**    ****QCD diphoton, **
-     **jet mis-ID, W+photon (lost track)**
** **_**Results:**_
**    ****1392(97)events for Et>13(25)**** **

**   **_**For Missing Et>25GeV**_
**Expected background:   ****2********2**** **
**Observed: ****	****               ****2**

** ****Gravitino: the LSP particle**
** ****NLSP: Neutralino N****1******** ********G **
** ****Experimental Signature: ********+Met**

**Limit on GMSB Model**

**Missing Et Spectrum**

****** ****Set cross section limit, now**_** **_

**SUSY would show up as an excess of events with large Missing Energy**

## Search GMSB for +      (II)

**Set the lower mass limit on the lightest**
**chargino in GMSB:**_** **_
**           **_**M**__**c**__**>113 GeV @ 95% C.L.**_

**Acceptance**

**Event Expected**

## Search for New Physics in +

-  - **one ******** with E****T ****> 47 GeV and |********|<1**
** ****- Missing E****T ****> 42 GeV**
** ****- No jets with E****T ****> 10 GeV**
** ****- No tracks with p****T ****> 5 GeV**** **** **

**Results: **_**No excess was found**_
**Expected background: 18.0 ******** 2.1  **
**Observed: ****	****             17**

| Cosmic ray muons | 3.9  1.0 |
| --- | --- |
| Z  + | 4.8  0.5 |
| W  e | 7.3  1.7 |
| QCD diphotons | 1.1  0.4 |
| W ()  | 0.9  0.3 |

**Main backgrounds: **

**(84 pb****-1 ****) **

**Randall-Sundrum**

_**Search for New Physics in**__** **____**+**_

_**95% C.L. upper limit on**_** **
**(**_**accep.**_** x  **_**eff.**_** x **_**cross-section**_**) of**
**121 fb was set****: ****(2.1 x expected Z******** signal)**** **

_**Limit on New Physics**_

**ADD**

**Extra Dimensions**

## Search for Excited Electrons

**Since cross-section depends on M****e***** & ****Λ****,  we obtain exclusion region using various values of ****M****e***** and ****Λ**

** ****Search for the production of ****excited**** or ****exotic**** electrons (e*) in the**
**   ****following reaction:**
** ****This is a signature-based search for an *****ee*********  final state with a resonance in**
**    ****the e******** channel; ****select two high p****T**** electrons ******** one photon (Et>25 GeV)**** **
** ****0 event observed,**** set the **_**first mass limit on the e***_**  ****for contact interaction**
**   ****model.**** ****For**** ****M****e***** = ****Λ****,  the mass limit is ****785 GeV**

** ****M(e*)<785 GeV**

**Λ**** = Compositeness Scale**

## W Production with We at CDF

|  | Data | BGD | •B(Wl) (pb) |
| --- | --- | --- | --- |
| e | 43 | 33% | 17.2±3.8stat±2.8sys±1.0lum |
|  | 38 | 29% | 19.8±4.5stat±2.4sys±1.2lum |

***W********* Production with *****W**********e************************* at CDF**

** ****Physics: **_**look for evidence of  anomalous coupling (New Physics)**_
** ****Signature: ****one high p****T**** lepton(e********) ******** **
**   ****with MET(>25),  (********R(********-l)>0.7) **
** ****Results:**** **_**No excess was found**_
**   ****Data: ****	****                                 43(38)**
**   ****Signal MC+Background : 46.6 ******** 1.3 ******** 4.5**** **
**                                              ****(36.5 ******** 0.7 ******** 3.0)**** **

**... ****derived the  cross section for**
**Et(********)>7, ********R>0.7**

**Results consistent with SM**
_**SM: **__****__**•B(W**__****__** **__****__**l**__****__**) = 18.7 ± 1.3 pb**_

## Z Production with Zee at CDF

** ****Physics: **_**look for evidence of  anomalous coupling (New Physics)**_
** ****Signature: ****two high p****T**** lepton(e********) ******** **
**   ****(********R(********-l)>0.7) **
** ****Results:**** **_**No excess was found**_
**   ****Data: ****	****                   11(14)**
**   ****Signal MC+BGD : 10.8 ******** 0.9 ******** 0.6**** **
**                                ****(12.4 ******** 1.2 ******** 0.7)**

|  | Data | BGD | •B(Zll) (pb) |
| --- | --- | --- | --- |
| e | 11 | 4.6% | 5.5±1.7stat±0.6sys±0.3lum |
|  | 14 | 4.0% | 6.0±1.6stat±0.7sys±0.4lum |

**Results consistent with SM **
_**SM: **__****__**•B(Z**__****__****__**ll**__****__**) = 5.4 ± 0.4 pb**_

**X-section for Et(********)>7, ********R>0.7**

_**W**_****_**/Z**_****_** **__**data are in good agreement w/ SM**_

## Conclusions

**CDF II is taking data actively since 2001 and larger samples are being collected/tested for new physics searches based on photon signature.**
**It is producing its first results on new particle searches with photons. Two different approaches for new physics searches are in progress in CDF.**
_**Signature based searches**_
_**Model based searches**_
**High luminosity photon data will ****provide... **
**the best opportunity for new physics discoveries, and will give any useful informations to theorists. ****(******** Signature-based searches)**
**experimental guidance to a better theoretical modeling**** of new physics production with photon in the final states ****(******** Model-based searches)**

**Conclusions**

## Backup Slides

## Run I - Lepton+Photon Searches

**CDF has performed a **_**model independent search**_** in Run I for new physics that gives leptons, photons, missing E****T**** in final state**
**Inspired by *****ee**********+*****        ****candidate event**

**The SM prediction yields the observed rate of a lepton+photon (+Missing Et) with 0.7% probability **_**(~2.7 standard deviation for Gaussian distribution)**_** **

**Recent theoretical explanation of the **************events is...******
_**“**__**Resonant smuon production with a single dominant R-parity violating coupling”**_**  ****(hep-ph/0111014)**

** **_**Search Selection:**_**   *****l(e******/************)*********events (Et>25 GeV)**
** **_**Main backgrounds**__:_** **
**   ****W/Z+********, lepton+fake ******_** **_

_**It’s an interesting result, but it’s **__**not a compelling observation**__** of new physics!!**_
**Run II analysis is**
** ****in progress now**

## CDF I Photon-based New Physics Searches

**Search for Diphoton and *****E******T***
****** ****Gauge-Mediated SUSY Breaking***** ******(************ in ************+ E******T ******+ X)***
**Search for Narrow Diphoton Resonances**
****** ****Bosephilic Higgs Search**
****** ****Sgoldstino Search**
**Search for Photon and B-jet**
****** ****MSSM***** (************2******0****** ******************1******0************via ******g, q******)***
********* *****Technicolor***** (************T******  ************ ************T****** ************ ************bb****** ************ ************+ 2 b-jets******)***
**Search for Photon and Lepton**
********* ******e************+ E******T  ************+ E******T  ******,e************+ E******T  ***
**Search for LED with Diphotons**
****** ****S-channel production of KK tower of Gravitions**
**Search for Photon and *****E******T***

**~**

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## Run II has started, searches are in progress