# Presentation: 170578

## Searches for New PhenomenaWith the D Detector

- Searches for New PhenomenaWith the D Detector
- Nick Hadley
- The University of Maryland

## Outline

- Detector and Accelerator Status
- Search for Extra Dimensions
- Large Extra Dimensions
- Tev-1 Extra Dimensions
- Randall Sundrum Model
- Search for SUSY
- Trilepton Search

## Tevatron Run II Status

- Significant upgrade of Detectors and accelerator
- New Main Injector and antiproton recycler
- Higher energy 1.8 TeV → 1.96 TeV
- Shorter bunch crossing time (396 ns) and more bunches (6x6 → 36 x 36)
- Projected Integrated Luminosity per experiment: 2 fb-1 by 2006, 8 fb-1 by 2009
- Highest L to date 1.03 x 1032 cm-2 s-1
- Nearly 0.5 fb-1 on tape to date
- Data taking efficiency 85%-90%

## Fy2004 Tevatron Performance Goal Exceeded

- 106% of Design Goal
- at
- 96% through the Fiscal Year

## Slide 5

## D Detector

- 2T Solenoid
- Silicon detector
- Fiber Tracker
- Upgraded Muon system
- Upgraded DAQ/trigger

## Integrated Luminosity

- Integrated Luminosity more than doubled in the last 12 months

## Models of Extra Dimensions

- ADD Model:
- “Eliminates” the hierarchy problem by stating that physics ends at a TeV scale
- Only gravity lives in the “bulk” space
- Size of ED’s (n=2-7) between ~100 m and ~1 fm
- Doesn’t explain how to make ED large

- TeV-1 Scenario:
- Lowers GUT scale by changing the running of the couplings
- Only gauge bosons (g//W/Z) propagate in a single ED; gravity is not in the picture
- Size of the ED ~1 TeV-1 or ~10-19 m

- RS Model:
- A rigorous solution to the hierarchy problem via localization of gravity
- Gravitons (and possibly other particles) propagate in a single ED, w/ special metric
- Size of this ED as small as ~1/MPl or ~10-35 m

## Kaluza-Klein Spectrum

- ADD Model:
- Winding modes with energy spacing ~1/r, i.e. 1 meV – 100 MeV
- Can’t resolve these modes – they appear as continuous spectrum

- TeV-1 Scenario:
- Winding modes with nearly equal energy spacing ~1/r, i.e. ~TeV
- Can excite individual modes at colliders or look for indirect effects

- RS Model:
- “Particle in a box” with a special metric
- Energy eigenvalues are given by zeroes of Bessel function J1
- Light modes might be accessible at colliders

**~M****GUT**

**E**

**...**

**M****0**

**M****i**

**~M****Pl**

**E**

**...**

**M****1**

**M****i**

## Collider Signatures: Large Extra Dimensions

- Kaluza-Klein gravitons couple to the energy-momentum tensor, and therefore contribute to most of the SM processes
- For Feynman rules for GKK see:
- Han, Lykken, Zhang, [PRD **59**, 105006 (1999)]
- Giudice, Rattazzi, Wells, [NP **B544**, 3 (1999)]
- Since graviton 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
- Depending on whether the GKK leaves our world or remains virtual, the collider signatures include single photons/Z/jets with missing ET or fermion/vector boson pair production
- Graviton emission: direct sensitivity to the fundamental Planck scale MD
- Virtual effects: sensitive to the ultraviolet cutoff MS, expected to be ~MD (and likely < MD)
- The two processes are complementary

## Intermediate-size extra dimensions with TeV-1 radius
Introduced by Antoniadis [PL B246, 377 (1990)] in the string theory context; used by Dienes, Dudas, Gherghetta [PL B436,  55 (1998)] to allow for low-energy unification
Expect ZKK, WKK, gKK resonances at the LHC energies
At lower energies, can study effects of virtual exchange of the Kaluza-Klein modes of vector bosons
Current indirect constraints come from precision EW measurements: 1/r ~ 6 TeV
No dedicated experimental searches at colliders to date

- Intermediate-size extra dimensions with TeV-1 radius
- Introduced by Antoniadis [PL **B246**, 377 (1990)] in the string theory context; used by Dienes, Dudas, Gherghetta [PL **B436**,  55 (1998)] to allow for low-energy unification
- Expect ZKK, WKK, gKK resonances at the LHC energies
- At lower energies, can study effects of virtual exchange of the Kaluza-Klein modes of vector bosons
- Current indirect constraints come from precision EW measurements: 1/r ~ 6 TeV
- No dedicated experimental searches at colliders to date

- Antoniadis, Benaklis, Quiros [PL **B460**, 176 (1999)]

- ZKK

- TeV-1 Extra Dimensions

## Randall-Sundrum Scenario

- Randall-Sundrum (RS) scenario [PRL **83**, 3370 (1999); PRL **83**, 4690 (1999)]
- + brane – no low energy effects
- +– branes – TeV Kaluza-Klein modes of graviton
- Low energy effects are given by ; for krc ~ 10,  ~ 1 TeV and the hierarchy problem is solved naturally

- G

- Planck brane

## RS Model Parameters

- Need only two parameters to define the model: k and rc
- Equivalent set of parameters:
- The mass of the first KK mode, M1
- Dimensionless coupling

- Drell-Yan at the LHC

- M1

- Davoudiasl, Hewett, Rizzo [PRD **63**,** **075004 (2001)]

- To avoid fine-tuning and non-perturbative regime, coupling can’t be too large or too small
- 0.01 ≤              ≤ 0.10 is the expected range
- Gravitons are narrow

- Expected Run II sensitivity in DY

## Search Strategy

- ED processes predict high mass di-lepton and/or di-photon events
- Study High Pt di-electron, di-muon, and di-photon mass spectra
- Main backgrounds: Drell Yan and QCD jet events where jets fake leptons and photon
- Drell-Yan: shape vs mass known from theory
- QCD: get shape from events that (just) fail particle ID cuts.
- Normalize DY and QCD to “low mass” events (typically about 50 GeV to 120 GeV) includes Z.

## Example: diEM Mass 

## No excess seen

- No excess of di-lepton or di-photon events is seen. (Typical luminosities 200 pb-1)
- Set limits...

## Virtual Graviton Effects

- In the case of pair production via virtual graviton, gravity effects interfere with the SM (e.g., *l*+*l*- at hadron colliders):
- Therefore, production cross section has three terms: SM, interference, and direct gravity effects:

- The sum in KK states is divergent in the effective theory, so in order to calculate the cross sections, an explicit cut-off is required
- There are three major conventions on how to write the effective Lagrangian:
- Hewett [PRL **82**, 4765 (1999)]
- Giudice, Rattazzi, Wells [NP **B544**, 3 (1999); revised version, hep-ph/9811291]
- Han, Lykken, Zhang [PRD **59**, 105006 (1999); revised version, hep-ph/9811350]
- Fortunately all three conventions turned out to be equivalent and only the definitions of MS are different

## DØ Search for Virtual Graviton Effects

- Combine diphotons and dielectrons into “di-EM objects” to maximize efficiency
- High-mass, low |cos| tail is a characteristic signature of LED Cheung, Landsberg [PRD **62**, 076003 (2000)]

- Sensitivity is dominated by the diphoton channel (2  1 + 1)
- Data agree well with the SM predictions; proceed with setting limits on large ED: alone or in combination with published Run I result [PRL **86**, 1156 (2001)]:
- These are the most stringent constraints on large ED for n > 2 to date, among all experiments, (tabletop gravity n= 2, M>1.7TeV, r < 160m)

**200 pb****-1**

|       Hewett |  | GRW |                        HLZ         (TeV, @95% CL) |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| = +1 | = 1 |  | n = 2 | n = 3 | n = 4 | n = 5 | n = 6 | n = 7 |
| 1.22 | 1.10 | 1.36 | 1.56 | 1.61 | 1.36 | 1.23 | 1.14 | 1.08 |
| 1.28 | 1.16 | 1.43 | 1.67 | 1.70 | 1.43 | 1.29 | 1.20 | 1.14 |

| 170 m | 1.5 nm | 5.7 pm | 0.2 pm | 21 fm | 4.2 fm |
| --- | --- | --- | --- | --- | --- |

**r****max**

- MS = 1 TeVn=6

## DØ Search for Virtual Graviton EffectsDi-muon channel

- Preliminary Di-muon results just approved
- 250 pb-1, no deviations from SM seen.

|       Hewett |  | GRW |                        HLZ         (TeV, @95% CL) |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| = +1 | = 1 |  | n = 2 | n = 3 | n = 4 | n = 5 | n = 6 | n = 7 |
| 0.97 | 0.95 | 1.09 | 1.00 | 1.29 | 1.09 | 0.98 | 0.91 | 0.86 |

## Interesting Candidate Events

- While the DØ data are consistent with the SM, the two highest-mass candidates have low values of cos* typical of ED signal:

- Event Callas: Mee = 475 GeV, cos* = 0.01

- M = 436 GeV, cos* = 0.03

## First Dedicated Search for TeV-1 Extra Dimensions

- While the Tevatron sensitivity is inferior to the indirect limit, it’s searching for effects of virtual KK modes, as they are complementary to those in the EW data
- DØ has performed the first dedicated search of this kind in the dielectron channel based on 200 pb-1 of Run II data (ZKK, KK  e+e-)
- The 2D-technique similar to the search for ADD effects in the virtual exchange yields the best sensitivity in the DY production Cheung, Landsberg [PRD **65**, 076003 (2002)]
- Data agree with the SM predictions, which resulted in the following limit on their size:
- 1/r > 1.13 TeV @ 95% CL
- r < 1.75 x 10-19 m

- 200 pb-1, e+e-

- Event
- Callas

- Interference effect

**1/r = 0.8 TeV**

## DØ Search for RS Gravitons

- Analysis based on 200 pb-1 of e+e- and  data – the same data set as used for searches for LED
- “Naturally” combine two channels by NOT distinguishing between electrons and photons!
- Search window size has been optimized to yield maximum signal significance
- Analysis technique is similar to CDF’s; acceptance is higher due to forward photons

## DØ Limits in the ee+ Channel

- Already better limits than the sensitivity for Run II, as predicted by theorists!

- Assume fixed *K*-factor of 1.3 for the signal

- Masses up to 780 GeV are excluded for *k*/*M**Pl* = 0.1

- The tightest limits on RS gravitonsto date

- CDF 

**D****Ø Run II Preliminary, 200 pb****-1**

**D****Ø Run II Preliminary, 200 pb****-1**

- Hot!

## Extra Dimension Summary

- No di-electron, di-muon or di-photon excess seen
- Set LED, TeV-1 and RS limits
- Z’ limit
- 780 GeV at 95% CL (ee 200 pb-1)
- 680 GeV at 95% CL ( 250 pb-1)
- Check www-d0.fnal.gov/Run2Physics/WWW/results/NP/np.htmfor updates and details (D Searches public results page)

## SUSY

- Numerous results including searches for RPV SUSY.
- All limits (unfortunately)
- See (same page as before) for details www-d0.fnal.gov/Run2Physics/WWW/results/NP/np.htm
- One example: trilepton search

## Trilepton Chargino and Neutralino Search

- Associated production of lightest chargino and next to lightest neutralino in tri-lepton channels
- Results interpreted in mSUGRA model
- Tan  = 3,  > 0, A0 = 0
- Four channels combine overlaps removed
- Two electrons + third lepton (249 pb-1)
- Electron + muon + third lepton (221 pb-1)
- Two muons + third lepton (235 pb-1)
- Two like sign muons (147 pb-1)
- Third lepton = isolated track (for higher efficiency)

## Trilepton Chargino and Neutralino Search (cont)

- No excess of events seen in any single channel or in all channels combined
- see 3 events total
- expected background = 2.93 events)
- Set limits...
- Significant improvement over Run 1 results
- Will reach mSUGRA interesting region with about 25% more data (have x2 on tape)

## Trilepton Chargino and Neutralino Search (cont)

## Summary

- D is actively searching for new phenomena and particles in our data. Techniques are maturing, sensitivities substantially exceed old bounds
- Detector and accelerator performing well.
- Only limits so far...
- Let us know about your favorite model
- We’re glad to look...