Searches for New Phenomena With the D Detector Nick Hadley The University of Maryland

Searches for New PhenomenaWith the D Detector

Nick HadleyThe University of Maryland

N. Hadley PASCOS 2004

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

0

50

100

150

200

250

300

350

400

0 30 60 90 120 150 180 210 240 270 300 330 360

Days Since October 1

Inte

grat

ed L

umin

osity

(pb

-1)

FY04

FY03

FY02

FY04 Design

FY04 Design with Pbar Tax

FY04 Base

FY04 Base with Pbar Tax

106% of Design Goal at

96% through the Fiscal Year


AØ: The High Rise

BØ: CDF

CØ: Future BTeV

FØ: The RF

EØ: This Space For Rent

DØ:


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

G

Planck

brane

x5

SM brane


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

~1 TeVE ~MGUT

E

…

M0

Mi

2220 riMM i

~MPl

E

…

M1

Mi

... ,30.4 ,48.3 ,66.2

,83.1 ,;0

111

11110

MMM

MMxxMMM ii


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

Real Graviton EmissionMonojets at hadron colliders

GKK

gq

q GKK

gg

g

Single VB at hadron or e+e- colliders

GKK

GKK

GKK

GKK

V

VV V

Virtual Graviton Emission Fermion or VB pairs at hadron or e+e- colliders

V

V

GKKGKK

f

ff

f


• 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 branex5

SM 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 PlMk /

Drell-Yan at the LHC

M1

PlMk /

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 narrowPlMk /

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

MfM

naMf

M

na

dMd

d

dMd

d

SS

SM

,cos,cos

coscos

*28

2*

14

*

2

*

2


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 < 160m)

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 1.14170 m

1.5 nm

5.7 pm

0.2 pm

21 fm

4.2 fm

rmax

MS = 1 TeVn=6


DØ Search for Virtual Graviton EffectsDi-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-

EventCallas

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/MPl = 0.1

The tightest limits on RS gravitonsto date

CDF

DØ Run II Preliminary, 200 pb-1

DØ Run II Preliminary, 200 pb-1Hot!


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…

Searches for New Phenomena With the D Detector Nick Hadley The University of Maryland

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