Search for Extra-Dimensions at D0

Search for Extra-Dimensions at D0

Tevatron and D0 status Extra Dimensions

• Large ED• Tev-1 ED• Randall Sundrum Model

M. Jaffré

LAL Orsay

for the D0 Collaboration

DD

M.Jaffré EuroGDR Nov 24, 2004 2

DDNew Main Injector: 150 GeVNew RecyclerHigher Energy (1.96TeV)

Higher luminosity ( 36x36 bunches)

Design “Run IIa” : 0.8x1032 cm-2s-1

“Run IIb” : 2-4x1032 cm-2s-1

Upgrades to comeSlip stacking end 04

Electron cooling end 05 ?

Stacktail upgrade end 06 ?

New helix beam separation end 06 ?

Projected Integrated lumi. / expt:2006 2fb-1

2009 8fb-1

Tevatron RunII Status

1.02 1032 cm-2 s-1

2002 2003 2004

Run I record


DD

SMTSMT

SMT

DØ Run II

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

For Run IIb (Fall 05) Silicon layer 0 Trigger upgrade


DD Half A Femtobarn of Data!

D0 analysis

Integrated Luminosity more than doubled in the last 12 months

Efficiency >80%


DD Why ED ?

String theory is the only currently known way to incorporate gravity in Quantun Mechanics.

ED come « naturally » with string theory (n=6 or 7)

In short, models with ED try to address the problem of the huge hierarchy between EW and Planck scales.

….

These ideas can be tested at existing and nearly existing colliders


DD Models of Extra Dimensions

ADD Model:Arkani-Hamed,Dimopoulos,Dvali

Phys Lett B429 (98) SM particles and gauge

bosons are confined in D3-brane

Only gravity propagates in n spatial ED

Gauss law

MPl (apparent 4D Planck Scale)

MD (fundamental Planck Scale)

Size of ED’s (n=2-7) between ~100 m and ~1 fm

TeV-1 Scenario:Dienes,Dudas,Gherghetta Nucl Phys

B537 (99) 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:Randall,Sundrum Phys Rev Lett 83

(99) 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

M2Pl MD

n+2 x Rcn


DD Kaluza-Klein Spectrum

ADD Model: KK excitations with

energy spacing ~1/r, i.e. 1 meV – 100 MeV

Can’t resolve these modes – they appear as continuous spectrum

TeV-1 Scenario: KK excitations with nearly

equal energy spacing ~1/r, i.e. ~TeV

Can excite individual modes at colliders or look for indirect effects

RS Model: Coupling of graviton to SM

fields is : k/MPl [0.01-0.1] Light modes might be

accessible at colliders Model characterized by M1

and k/MPl

~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


DDCollider 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


DD Search for Monojets

Very challenging because of instrumental background from MET mismeasurement, cosmics.

Irreducible Physics background from Z() + jet(s). Special trigger for Physics with jets and MET since

spring 03 : MHT = pT(jets) > 30 GeV/c 85 pb-1 (april-august 2003) Calorimeter Data Quality is very important for Jet+Met

analyses, since most calorimeter problems (hot cells, noise...) will increase the MET tail distribution

Offline: to fight mixvertexing and cosmics :jets have associated tracks originating from primary vertex


DD

63N

(JES)7.5(theo)6.2(stat) 100.2 N

observed

5030 -expected

Final Selection :

-Leading jet pT > 150 GeV(||1)

-Isolated electron and muon veto

-MET > 150 GeV

-No extra jet with pT > 50 GeV

-MET separated from any jet by 30

Signal simulation = Pythia + Lykken-Matchev code

(~ 5% signal efficiency)

Largest uncertainty is from JES and have already been much improved

With 85 pb-1 better than D0 Run I

still below CDF Run I

Search for Monojets

N=6

MD = 0.7 TeV

QCD bckg

Mostly Z()+jetsbefore MET cut


DD Search for effects in high mass dilepton, diphoton events

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 photons

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.


DD LED 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 Xsection has three terms: SM, interference + direct gravity effects:

where G= F/MS4

Hewett: F = 2/ with = ± 1 GRW: F = 1 HLZ: F = log(MS

2/s) for n = 2 F = 2/(n-2) for n > 2

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

An expected value of the cut-off MS MD,as this is the scale at which the effective theory needs to be used to calculate production.

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

2int

2

cosM GKKGSM fffdd

d

cos = |cosine| of scattering angle in c.o.m frame


DD diEM Selection

min. Mass Data Bckg

300300

350350

400400

450450

480480

14 14

88

55

11

00

17.317.3

8.18.1

4.44.4

2.6 2.6

1.9 1.9

Signal G=0.6 TeV-4

200 pb-1

DiEM = ee + 2 EM objects ET > 25 GeV

Track isolation

CC : ||1.1; EC : 1.5<||2.4

Overall ID efficiency 851% / EM

QCD

DY

+

Direct +

QCDSource of systematics Uncertainty

K-factor

Choice of p.d.f.

Luminosity x efficiency

ET dependence of efficiency

10%

5%

2%

5%

Total 12%


DD Search for LED in diEM channel Combine diphotons and dielectrons into “di-

EM objects” to maximize efficiency Sensitivity is dominated by the diphoton

channel (spin 2 graviton 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)]:

G95% = 0.292 TeV-4

Translated into the following mass limits RunII result Combined RunI + RunII result

These are the most stringent constraints on large ED for n > 2 to date, among all the experiments

200 pb-1

HewettGRW

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

rmaxMS = 1 TeVn=6

See these 2 evts in next slide


DD Interesting Candidate Events

Mee = 475 GeV, cos* = 0.01 M = 436 GeV, cos* = 0.03


DD 2 ’s with pT > 15 GeV

isolated, ||<2.0 for M > 300 GeV: Nexp = 6.40.8 and Nobs = 5 Systematics: ~ 13%

Search for LED in diMuon channelSearch for LED in diMuon channel

Hewett

GRW

HLZ (TeV, @95% CL)

l = +1 l = -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

Fit the 2D Fit the 2D distributions as for distributions as for diEMdiEM

GG95%95% = 0.72 TeV = 0.72 TeV-4-4

(Bayesian)(Bayesian)250pb-1


DD Apply the same 2D-technique as for LED

search.

Z/ KK states effects parameterized by

C=2/3MC2

Data agree with the SM predictions, which resulted in the following limit on their size:

MC > 1.12 TeV @ 95% CLr < 1.75 x 10-19 m

Well below indirect contraints from EW measurement (6 TeV)

Search for TeV-1 ED

signal for

C = 5 TeV-2

Di-electron channel 200 pb-1

QCD fake bckg much reduced compare to diEM

CC-CC

Note the negative interference


DD 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

Search window size has been optimized to yield maximum signal significance;

G(1) is narrow compare to the mass resolution

300 GeV RS signal

QCD DY+direct + QCD


DD 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 785 GeV are excluded for k/MPl = 0.1

The tightest limits on RS gravitonsto date

DØ Run II Preliminary, 200 pb-1

DØ Run II Preliminary, 200 pb-1


DD Conclusion - Outlook

The data agree well with the Standard Model New limits from D0 on Extra Dimensions

Twice the statistics is available, … more will come soon

Expect to increase the mass limits for LED models up to 2TeV before the LHC startup

Topic Prelim. Results

LED : ee + :

MS >1.43 TeV (GRW Run 1&2)

MS > 1.09 GeV

TeV-1 ‘longitudinal’ ED: ee Mc > 1.12 TeV

RS: ee + M(G(1)) > 785 GeV for k/MPl=0.1

Documents

Search for Extra-Dimensions at D0