D
Status of “some”
New Physics Searches at D
E. Kajfasz
for ...
CERN 12/09/06
E. Kajfasz
1
D
The Stage
Fermilab, Tevatron and D0
D
Chicago

Run I
(92-96)
1.8 TeV
~0.1 fb-1
Top discovery
...
p
p
1.96 TeV
Booster
p
CDF
DØ
Tevatron
p source
CERN 12/09/06
p
Main Injector
& Recycler
E. Kajfasz
Run II
(IIa 01-Feb 06)
(IIb Jun 06 ->...)
1.96 TeV
-> 8fb-1
Precision
measurements:
mt, mW, Dms
Searches for Higgs
and BSM
...
3
D
Tevatron status at the end of Run IIa (Feb. 06)
2002
Tevatron works well and
keeps getting better
2003
2004
1.5 fb-1
2005
Delivered Int. Luminosity / Expt
1 fb-1
just with
performances reached
at Run IIa
=> > 4 fb-1 en 2009!
Record Luminosity: 1.8  1032 cm-2 s-1
Integrated Luminosity:
record: 27 pb-1 /semaine/expt
delivered: 1.5 fb-1 /expt
on tape: 1.3 fb-1 /expt
pbars peak stacking rate > 20 mA/h
CERN 12/09/06
E. Kajfasz
4
Luminosity evolution for Run II
D
Integrated Luminosity (fb-1)
9
Run IIa Run IIb
Sep 09:
double
8
30 mA/hr
design
7
25 mA/hr
6
Sep 07:
double
5
4
3
2
Sep 05:
double
20 mA/hr
pbars peak
stacking rate
15 mA/hr
base
Sep 06:
double
1
0
9/30/03
9/30/04
9/30/05
9/30/06
9/30/07
9/30/08
9/30/09
- last shutdown started ~ Mar 1, 2006 => transition Run IIa/Run IIb
- Run IIb first store occured on Jun 9: D0 was ready to take data
CERN 12/09/06
E. Kajfasz
5
D
Upgrades for Run II
Run IIa Upgades
- Muon system
- CAL Electronics
- DAQ
- Trigger system
New at Run IIb
- L1 CAL
Tracker
Solenoid Magnet
- L1 Track
- Layer 0 for SMT
New at Run IIa
- Solenoid
- Silicon detector
- Fiber tracker
- Preshowers
protons
3 Layer
Muon
System
CERN 12/09/06
Electronics
E. Kajfasz Preshowers
6
Trigger commissioning
D
Run IIb installation and commissioning is a success !
Started data taking within
minutes of first Run IIb sore
Lumi
L1
L2
L3
CERN 12/09/06
E. Kajfasz
7
D
Layer 0 Commissioning
and operational
L0 is installed
cosmic
run
Threaded inside the
existing detector on a
new beam pipe at 1.6 cm
from the beams
CERN 12/09/06
E. Kajfasz
Physics
run
S/N=18
8
Operations
D
Efficiency back to ~90% by the third month of Run IIb operations
last
shutdown
90%
Detector/trigger
/DAQ downtime
~ 5%
Store and run
transitions
~ 2-3%
FEB ~ 3-5%
CERN 12/09/06
04/02
E. Kajfasz
08/06
9
D
Some ID tools
D
t-ID
(narrow jet)
CERN 12/09/06
E. Kajfasz
11
D
b-ID: different tagging algorithms ...
-
Secondary Vertex (SVT)
Jet Lifetime Impact Parameter (JLIP)
Counting Signed Impact Parameter (CSIP)
Soft Lepton
certified operating points
New b-tagging tool
- Combines various variables from the
track based b-tagging tools in a Neural
Network
- Substantial improvement in performance
over constituent input b-taggers
CERN 12/09/06
E. Kajfasz
12
D
New Physics Searches
Standard Model
D
Based on:
- 4-D space-time
- Poincaré group
- SU(3)c x SU(2)L x U(1)Y
- 3 generations of quarks and leptons
- Higgs mechanism
Phenomenologically
successful so far,
but many questions
unanswered...
Higgs field filling our Universe and
slowing down elementary particles.
Is it elementary?
If so, some drawbacks:
• no dynamical explanation to EWSB
• unnatural, requires fine tuning
-> MH unstable against rad. corr.
• in GUTs, leads to hierarchy problem
-> 2 very different scales
• no insight to flavor physics
CERN 12/09/06
E. Kajfasz
14
D
Some Ways to go Beyond ...
To answer some of
the questions ...
new theories and
models
- Alternative EWSB mechanisms -> Technicolor
- Relate quarks and leptons -> Leptoquarks
- Compositeness -> scale, m*, q*
- Enlarge the gauge group -> W’
- Extend Poincaré -> Supersymmetry
and include gravitation (Supergravity)
- Increase number of dimensions -> LED & RS
Notes, results, and publications on New Physics can be found at:
http://www-d0.fnal.gov/Run2Physics/WWW/results/np.htm
http://www-d0.fnal.gov/Run2Physics/WWW/results/higgs.htm
CERN 12/09/06
E. Kajfasz
15
D
Technicolor
Technicolor
D
Technicolor (TC - first introduced by Weinberg and Susskind):
New strong dynamics ‘a la QCD’ SU(NTC) -> TC condensates of technifermions
Coupling of condensates with unbroken electroweak gauge fields -> mass to W&Z
Extended TC (ETC) [mass and mixing to quarks and leptons]
Walking Technicolor (WTC) [flavor changing neutral current in ETC]
Topcolor-assisted Technicolor (TC2) [high value of mtop]
Technicolor Straw Man Model (TCSM2):
K. Lane, S. Mrenna Phys. Rev. D 67 (2003)
Framework to search for light technihadrons (relevant for Tevatron searches).
lightest technifermions expected to be an isodoublet of color singlets
-> color-singlet vector mesons: rT,wT
2 channels explored
-> color-singlet pseudo-scalar mesons: pT0,pT+/produced with substantial cross-section
rT 0/ wT 0 -> e+eat the Tevatron
cross-sections and branching fractions depend on:
r +/-  W+/- p 0
masses of rT and wT
technicolor charges of the technifermions
mass difference between vector mesons and technipions
2 mass parameters:
MA for axial-vector and MV for vector couplings
one expects MA = MV = few 100’s GeV
Implemented in PYTHIA [S. Mrenna]
CERN 12/09/06
E. Kajfasz
T
T
|
bb
 W-/+ pT+/| bc,bc
for m(rT)-m(pT) > mW
rT 0
17
D
wT/rT  e+e-
SELECTION:
2 isolated EM objects
at least 1 track matched
ET > 25 GeV
|h| < 1.1 or 1.5 < |h| < 2.4
BACKGROUND:
- Drell-Yan production
- QCD
- Search for rT/wT  e+e- as a
bump/excess at high dielectron
mass (intrinsic width < 1 GeV)
m(rT ,wT)-m(pT)= 60 GeV
m(rT ,wT)-m(pT)= 100 GeV
- Counting experiment in optimized
20-60 GeV windows centered
around rT/wT mass
CERN 12/09/06
E. Kajfasz
MV=500 GeV
MV=200 GeV
MV=100 GeV
18
W(en)pT(bb/c) event selection
D
q
Signal
rT W
W
q
pT

SM Background
e
n
b
b /c
Select W(en)+Heavy Flavor events
One isolated electron (EM TRIGGER)
pT > 20 GeV, |h| < 1.1
select W(en) events
veto on other electrons to suppress Z
Missing ET > 20 GeV, MT > 30 GeV
select W(en) events
eliminates multi-jets events
Two jets pT > 15 GeV, |h| < 2.5
estimated from data
At least one jet has to be associated
with a Secondary Vertex (b-tagging)
Veto on a third jet, suppresses tt
background
CERN 12/09/06
Instrumental Background
multijet production (mis-IDed electron)
W + light flavored jets (mistag)
E. Kajfasz
Cut based (CB) and
Neural Net (NN) analyses
19
Define kinematic and topological
quantities to extract the WpT signal
D0 Run II Preliminary 388 pb-1
M(pT) = 105 GeV M(rT) = 200 GeV MV = 500 GeV
HTe (electron pT + ∑ jet pT)
discriminates against tt
pT(jj) (pT of the dijet system)
discriminates against tt
D(jj) and D(e,MET)
against multijet and W + light quarks
M(jj) (inv. mass of the dijet system)
-> indication of pT narrow resonance
look for
M(Wjj) (W + dijet system)
concentration
-> indication of rT narrow resonance
Mass dependant optimization of cuts on S/√B
M(pT) = 105 GeV M(rT) = 200 GeV MV = 500 GeV
M(jj)
D
Cut based analysis
M(pT) = 110 GeV
M(rT) = 210 GeV
Data: 12
Bkg:
12.7 ± 0.9
Signal: 10.3 ± 1.0
CERN 12/09/06
E. Kajfasz
no excess
seen ...
M(Wjj)20
D
Neural Net analysis
2 stage NN using 8 kinematic
and topological variables
HTe, pT(jj), D(jj), D(e,MET),
pT(j1), pT(j2), pT(e), MET
Mass dependent optimization
on S/√B
M(pT) = 105 GeV M(rT) = 200 GeV MV = 500 GeV
D0 Run II Preliminary 388 pb-1
no excess
seen ...
CERN 12/09/06
E. Kajfasz
21
Result of the WpT analyses
D
Limits computed using:
- Bayesian statistics (CB)
- 2D maximum likelihood using
(M(Wjj),M(jj)) correlations (NN)
D0 Run II Preliminary 388 pb-1
First measurement done
with TCSM2 model
(cannot be compared with the
now obsolete TCSM)
95% CL
Observed Excluded (NN)
Expected Excluded (NN)
Observed Excluded (CB)
Expected Excluded (CB)
Forbidden Region
No evidence was found for
pT, rT production for the
parameters used with 388 pb-1
> 1 fb-1 is now available
Add m channels soon
Possibility of exploring larger
TC parameter space
CERN 12/09/06
E. Kajfasz
22
D
Leptoquarks
Leptoquarks
D
Predicted by many extensions of the SM
Carry both lepton and quark quantum numbers
=> connection of lepton and quark sectors
Description with effective couplings
invariant under SU(3)CxSU(2)LxU(1)Y
conserve lepton and baryon number separately (proton lifetime)
couple to lepton and quark in the same family (FCNC)
scalar and vector leptoquarks are possible but only limits for scalar
leptoquarks will be shown (lower X-sections and less model dependant)
Pair production modes:
- quark anti-quark annihilation
- gluon fusion
CERN 12/09/06
Decay: parameterized by b
the LQ branching fraction
to charged lepton + quark
E. Kajfasz
24
D
eejj:
1st generation leptoquarks
- 2 electrons ET>25 GeV
> 1 elec. track matched
> 1 elec. in CC
- >=2 jets ET>20 GeV |h|<2.4
- veto Mee in [80,102] GeV
- ST(e,e,j,j) > 450 GeV
enjj:
- 1 electron ET>35 GeV
in CC and track matched
- >=2 jets ET>25 GeV |h|<2.4
- veto on m’s w/ pT>10 GeV (tt)
- MET > 30 GeV
- Transv. mass(e,MET) (W)
- ST(e,MET,j,j) > 330 GeV
no excess
seen ...
CERN 12/09/06
E. Kajfasz
25
D
1st generation leptoquarks
enjj
eejj
256 GeV
CERN 12/09/06
E. Kajfasz
26
D
mmjj:
2nd generation leptoquarks
- 2 muons
cosmic vetos
matched to isolated tracks
|h| < 2.4
pT > 15 GeV
- >=2 jets ET>25 GeV |h|<2.4
- Mmm > 105 GeV (Z)
Data
6
Total Bkgs
6.8 ± 2.0
Z/DY
6.1 ± 2.0
tt
0.69 ± 0.07
no excess
seen ...
ST(m,m,j,j)
CERN 12/09/06
E. Kajfasz
27
D
2nd generation leptoquarks
4 bins used as individual channels
to extract limits using CLS
251 GeV
CERN 12/09/06
E. Kajfasz
28
D
Leptoquarks search in jets+MET
SIGNAL
Pair production modes:
- quark anti-quark annihilation
- gluon fusion
Decay: parameterized by b
the LQ branching fraction
to charged lepton + quark
Topology:
2 (light/b)-jets
+ missing energy
BACKGROUNDS
Standard Model (SM) :
‘QCD’ or instrumental:
(ALPGEN interfaced with PYTHIA)
- Vector boson production associated with jets
- Z + 2 jets  nn + 2 jets (irreducible)
- W + 2 jets ln + 2 jets (l = e, m,t)
(lepton not reconstructed)
- W + 1 jet  ln + 1 jet (l = e, t)
(lepton identified as a jet)
- diboson production : WW, WZ, ZZ
- top production (single and pair)
CERN 12/09/06
E. Kajfasz
- multijet production
determined from data
29
D
Leptoquarks in acoplanar jet topology
Selection
Start with ~ 14 million events collected with the Jets+MET trigger
Initial cuts:
- MHT =
> 40 GeV
- DF(2 leading jets) < 165o
- MET > 40 GeV
- |zPV| < 60 cm
- at least 2 jets
- data quality cuts
mLQ = 140 GeV
D(MET,j)
CERN 12/09/06
E. Kajfasz
30
D
leptoquarks in acoplanar jet topology
(Δφmax + Δφmin)
(Δφmax – Δφmin)
140 GeV
140 GeV
QCD
• Exp. and power law fits to
MET distrib. in range [40,60]
GeV after removal of the SM
contribution
• extrapolated at high MET
• Average result of the 2 fits
-> QCD background estimate
• Difference -> systematics
2.3 ± 1.2
CERN 12/09/06
E. Kajfasz
(for MET > 70 GeV)
31
D
leptoquarks in acoplanar jet topology
b = 0
mLQ > 136 GeV @ 95% CL
Most stringent limit for 1st and 2nd
generation scalar leptoquarks
decaying exclusively in a quark and
a neutrino (b=0)
what about the 3rd generation?
CERN 12/09/06
E. Kajfasz
32
D
3rd gen. LQ
Signal
Phase space suppression factor Fs
for higher masses
BR(LQ3->bn) = 1 – 0.5*Fs
charge 1/3
Use b-tagging to increase
sensitivity to signal
Selection
CERN 12/09/06
Decay:
BR(LQ3->bn) = 1
as long as M(LQ3) < M(t)+M(t)
E. Kajfasz
33
D
Using b-tagging
Two taggers used:
Jet LIfetime Probability (JLIP)
m-tag: if muon within a cone DR = 0.5 around the jet axis
2 b-tags are required:
at least 1 m-tag and at least 1 JLIP-tag
2 JLIP-tags and Xij > 0.8 (
)
@ 95% CL if LQ3
also decays in tt:
mLQ > 213 GeV
if not:
mLQ > 219 GeV
[B(LQ -> bn) = 1]
CERN 12/09/06
E. Kajfasz
34
D
Compositeness
Lepton-quark compositeness
Excited leptons and quarks
D
Lepton-Quark Compositeness
effective lagrangian
interference
term
(for e’s: m <-> e)
CERN 12/09/06
E. Kajfasz
contact
term
36
D
ee channel
Lepton-Quark Compositeness
270pb-1
SELECTION:
- 2 electrons w/ pT > 25 GeV
- in fiducial region and
|hdet| < 1.1 for CC
1.5 < | hdet | < 2.4 for EC
- at least one electron
track matched
BACKGROUNDS:
- Z/DY ee production
-multijets
estimated from data
- g+jets
estimated from multijets/g+jets ratio
No excess =>
95% CL limits on L
CERN 12/09/06
E. Kajfasz
37
D
Lepton-Quark Compositeness
mm channel
400pb-1
SELECTION:
- 2 muons w/ pT > 15 GeV
- |hdet| < 2.0
- Track quality cuts
- Cosmic ray cuts
- Isolation cuts
- Mmm > 50 GeV
BACKGROUNDS:
- Z/DY mm production
- t+t- and bb DY production
No excess =>
95% CL limits on L
CERN 12/09/06
E. Kajfasz
38
Excited Leptons and Quarks
D
Have the same quantum numbers as known leptons or quarks.
Occur in compositeness models where the known fermions are
bound states of more fundamental particles which are bound
together by a new strong interaction (L = Compositeness scale)
model of Baur, Spira, & Zerwas, PRD 42, 815, (1990)
 1/L2
Four-fermion Contact Interactions
CERN 12/09/06
E. Kajfasz
 1/L
Gauge mediated transitions
39
Excited muons m*
D
CI production and EW decay
BF CI/EW taken into account
SELECTION:
Two isolated muons pT > 15 GeV
One isolated photon |h| < 1.1, ET > 27 GeV
Mmg>200 GeV (varies with m* mass hypothesis)
Mmm
dimuon sample
Mmg
mmg sample
BACKGROUNDS:
Mainly mm DY
with ISR/FSR g
Others:
fake g, dibosons
CERN 12/09/06
E. Kajfasz
40
D
Excited muons m*
No excess =>
95% CL limits
CERN 12/09/06
mm* > 688
GeV for L = mm*
E. Kajfasz
41
D
Excited quarks q*
SELECTION:
- Two isolated electrons:
ET > 30, 25 GeV
|h| < 1.1 or 1.5 < |h| < 2.5
- One jet: ET > 20 GeV, |h| < 2.5
- 80 GeV < Mee < 102 GeV
- Final selection using MZj1 and pTZ
(depends on Mq* and Gq* [or x])
x = L/Mq*
BACKGROUND:
- Main background by far:
SM Z+jet production
- Instrumental backgrounds
(fake electrons) very small
MZj1
Mee
CERN 12/09/06
resonant
production
E. Kajfasz
42
Excited quarks q*
D
(MZj1 , pTZ ) optimized cut
No excess =>
95% CL limits
signal
region
Mq* > 510 GeV
for x = 1
CERN 12/09/06
E. Kajfasz
43
D
Extra Gauge Bosons
D
Search for W’ -> en
- Arises in SM extensions from the
presence of additional symmetry
groups
- Assumptions:
- no W, W’ mixing
- SM coupling
- W’ -> WZ channel supressed
- GW’ = 4/3 mW’/mW GW
SELECTION:
- 1 isolated track matched e
ET > 30 GeV and |h| < 1.1 (CC)
- MET > 30 GeV
- 0.7 < ET/MET < 1.3
- if jets w/ ET > 15 GeV
- D(e,j) < 2.5
- D(j,MET) < 2.5 (dijets)
CERN 12/09/06
mT = (2ET*MET(1-D(e,MET))1/2 [GeV]
- mT < 30 GeV
with loose e sample to normalize QCD
- 60 < mT < 140 GeV
overall normalization (900 pb-1)
- mT > 150 GeV
to look for W’ signal
E. Kajfasz
45
D
Search for W’ -> en
no excess
seen ...
CERN 12/09/06
E. Kajfasz
46
D
Supersymmetry
D
SUSY Particles and their SM partners differ in spin by 1/2
The SUSY
menu
CERN 12/09/06
More or less constrained MSSM, à la mSUGRA
- if mSUGRA: m0 m1/2 tan(b) A0 sign(m)
- neutralino LSP
-> R-Parity Conserving processes
-> charginos/neutralinos
-> generic squarks and gluinos
-> stop/sbottom
-> R-Parity Violating processes: LSP unstable
-> MSSM Higgs bosons
Gauge mediated SUSY breaking
- gravitino LSP and neutralino NLSP
-> 2 photons + MET
Anomaly mediated SUSY breaking
-> long-lived charged particles
Split SUSY
-> long-livedE.gluino
Kajfasz
48
D
“Trileptons” + MET
production
decay
Chargino-neutralino production
clean signature
=> Trilepton + MET
But Like Sign dileptons
particularly relevant for very
soft 3rd lepton (small c2slepton mass difference)
- low cross sections ( BR)
- soft leptons
- taus (at large tanb)
=> Need large integrated luminosity
=> Combine various final states
CERN 12/09/06
E. Kajfasz
49
eel + MET
D
SELECTION:
- Two isolated e’s
- An isolated 3rd lepton or track (sensitive to t’s)
- Missing ET
ee+l
Data are well described at the
preselection stage
2-4 signal evts expected
CERN 12/09/06
E. Kajfasz
50
D
LS mm + MET
Start with: two isolated LS m’s pT > 5 GeV
Data are well described at the
preselection stage
CERN 12/09/06
E. Kajfasz
1-4 signal evts
expected 51
“Trileptons” + MET
D
Analysis
channel
Lumin.
(fb-1)
Background
predicted
Observed
data
ee+track
1.1
0.760.67
0
m+m+/ m-m-
0.9
1.1  0.4
1
em+track
0.3
0.310.13
0
mm+track
0.3
1.750.57
2
eth+track
0.3
0.580.14
0
mth+track
0.3
0.360.13
1
Results of the various channels
are combined, “weighted”
according to their sensitivity,
with overlaps taken into account.
heavy-squarks:
destructive t-channel contribution minimal
3l-max:
sleptons degenerate and m(sl) slightly
greater than m(χ20). Leptonic BR enhanced
large m0:
at large slepton masses, W/Z exchange
dominant => small leptonic BR
CERN 12/09/06
m(c+) > 140 GeV
E. Kajfasz
52
D
Generic squarks & gluinos
SIGNAL: strong production
• sq-sqbar and sq-sq (sq  qc)
=> at least 2 jets + missing ET (MET)
@ small m0
• sq-gl (gl  qqc)
=> at least 3 jets + MET
@ intermediate m0
BACKGROUND:
- Instrumental
(QCD multijets with fake MET)
- (W(missed lepton)+n) +jets
(also from ttbar)
- (Z  nn) +jets (irreducible)
SELECTION:
• gl-gl
=> at least 4 jets + MET
@ high m0
3 optimized analyses
where QCD
background reduced
to negligible level
CERN 12/09/06
E. Kajfasz
53
Generic squarks & gluinos
D
“gluino” analysis
Analysis
Background
expected
Events
observed
 2 jets
4.8  4.5
6
 3 jets
3.9  1.5
4
 4 jets
10.3  2.4
10
Mgl > 387 GeV/c2 (when Mgl~Msq)
Mgl > 241 GeV/c2 ; Msq > 325 GeV/c2
CERN 12/09/06
E. Kajfasz
54
Stop
D
SIGNAL:
- stops pair produced (strong inter.)
- if sneutrino light
- em + MET and mm + MET analyses
optimized for various (m(st),m(sn))
ST = pT(e)+pT(m)+MET
em & mm combined
em
no excess seen ...
CERN 12/09/06
E. Kajfasz
55
Stop
D
SELECTION:
- 2 jets
 1 c-jet (“loose” b-tag)
- MET
- optimization on jet pT’s, MET and
D(j,MET) for various (m(st),mc)
SIGNAL:
- stops pair produced (strong inter.)
- if st NLSP and c LSP
m(st) < mb + mW + mc
BACKGROUND:
Mainly W+jets and Z(nn)+jets
m(st) = 130 GeV
m(c) = 50 GeV
131 GeV
CERN 12/09/06
E. Kajfasz
56
D
Sbottom
SELECTION:
- 2 or 3 jets ( 1 jet b-tagged)
- MET
- veto on isolated leptons/tracks
- angle between jets and MET
- optimization on jet pT’s, MET
for various (m(sb),mc)
SIGNAL:
- sbottoms pair produced (strong inter.)
- c LSP and B(sb->c+b) = 100%
BACKGROUND:
Mainly Z(nn)+jets, W(tn)+jets, and top
m(sb) = 140 GeV
m(c) = 80 GeV
CERN 12/09/06
222 GeV
E. Kajfasz
57
R-Parity Violation
D
possible terms in
superpotential
family
indices
lepton number
violation
difficult at
hadron collider
assume only one RPV coupling  0 at a time
At pp collider:
- RPC pair production, e.g. c+c-, c0c0, cc20,
with (cascade) decays to LSP’s
- followed by RPV decay
LLE couplings lijk
e.g.
a)
lijk > O(10-2): prompt decay
phenomenology independant of coupling
b) lijk < O(10-2): long-lived particule,
decay inside detector
CERN 12/09/06
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RPV: “large” LLE coupling lijk
D
l121
l122
set value
0.01
0.01
0.003
upper limit
0.5
0.085
0.005
channel
e.g.
l133
data
observed
bck
expected
ee+e/m
0
0.90.4
mm+m/e
0
0.40.1
tee
0
1.31.8
NN
validated with Ztt
CERN t-ID
12/09/06
~
c01
=> 4 charged leptons
(only 3 required)
and missing-ET
E. Kajfasz
m+
~
m-
ne
l121 e-
59
Small LLE coupling: long lived
D
DØ search motivated by 3 dimuon events in the NuTeV experiment
Production and decay model: SUSY RPV with a small l122
Look for displaced dimuon vertices (5-20 cm)
Calibrate with Kspp decays
Convert NuTeV
(pp at 38 GeV)
to DØ
(pp at 1.96 TeV)
0 data
0.81.6 bg.
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D
production
RPV: LQD coupling l’ijk
Because of QCD multijets and to be
able to reconstruct the neutralino and
smuon masses we want at least 2 muons
in the final state => 3 channels:
SELECTION:
2 isolated muons
pT1>15, pT2>8 GeV
at least 2 jets, pT>15 GeV
RECONSTRUCT:
m(χ10 ) leading μ + 2j
m(sm ) 2μ + all jet
du ->
du ->
c 20,3, 4  c10 qq' q' '...
dd ->
all channels combined
No signal observed =>
Exclusion for mass
and coupling derived
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D
GMSB: 2 g + MET
SELECTION:
- 2 central photons (|h| < 1.1), ET > 25 GeV
- MET > 45 GeV
- if jets, D(j, MET) < 2.5
BACKGROUND:
Essentially instrumental
- QCD with real photons or jets
mis-identified as photons
- W(en)+g, W(en)+j with e,j
mis-identified as photons
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effective scale of SUSY
SPS8
E. Kajfasz
m(c10) > 120 GeV
m(c1±) > 220 GeV
62
D
“Stable” lightest chargino
Stable = escapes the detector before decaying
Expected in some AMSB
models with small c1 – c10
mass difference
Pair produced => would
SELECTION:
-2 muons
- cosmics veto
- pT > 15 GeV
- D(m,m) > 1.0
=> Make use of the time
information of the muon
system scintillators
BACKGROUND:
muons w/ mismeasured time
estimated from data Z->μ μ
appear in DØ as slowlymoving “muons”
m(c1±) > 174 GeV
For a 150 GeV chargino:
0 data12/09/06
for 0.690.05 bkg
CERN
(1-b)/sb
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D
Stopped gluinos
In “Split-SUSY”, squarks are very-heavy => long-lived gluinos. Such gluinos form
R-hadrons which may stop in the DØ calorimeter. After a while, they decay into
e.g. a gluon + c10 (q-qbar-c10 also possible). (A. Arvanitaki et al., arXiv:hep-ph/0506242)
BACKGROUND:
beam and cosmic
muons, estimated
in data.
for sg -> g + c10
SELECTION:
look for a randomly oriented monojet
in empty event (diffractive trigger) Excludes gluino
- Central Jet in |h|<0.9
masses
- 90 GeV < E < 900 GeV
up to 300 GeV
- Dh and D of jet > 0.08 (wide jet)
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E. Kajfasz
m(c10 ) =
m(c10 ) =
200 GeV
50 GeV
m(c10 ) =
90 GeV
64
D
SUSY Higgs
Higgs bosons in MSSM
D
- 2 complex Higgs doublets: Hu (Hd)
couple to up- (down-) type fermions
- 8 Degrees of Freedom minus
W+/-, Z0 longitud. polar. states
 5 scalars predicted: h,H,A,H+,H- At tree-level, 2 independent params:
mA and tanb = <Hu>/<Hd>
- 5 more params from rad. corrections
MSUSY (mass scale of SUSY particles)
Xt = At – m cosb
(stop mixing)
M2
(gaugino mass term)
m
(Higgs mass parameter)
mgluino
At high tanb:
- Coupling of h/H/A (≡F0) with
‘down’-type quark (e.g. bottom)
quark and leptons enhanced over
the SM by a factor tanb
- A is almost degenerate with h/H
s(A)  s(h/H), G(A)  G(h/H)
Br(A->bb)  Br(h/H->bb) ~ 90%
Br(A/h/H->t+t-) ~ 10%
To search for F0:
F0b(b)->bbb(b) and F0 X -> t+t-X
(comes in via loops)
mhmax-scenario:
maximal mh(tanb) for fixed mt, MSUSY
no-mixing scenario:
no mixing in scalar top sector
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Search for b(b)0(->bb)
D
3 b-tags
Start from large multijet
trigger sample
Require at least 3 jets w/
displaced secondary vertex
Form invariant mass of two
leading b-jets, look for a bump
Shape and normalization of bkg
determined from double-tagged
data
260 pb-1
2 b-tags
m = - 200GeV
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Higgs bosons in the MSSM
D
Model dependence
Higher order corrections can be significant ...
SUSY loops => corrections
to bottom Yukawa coupling
on previous slide ...
m = - 200 GeV
mhmax better than no-mix
mhmax: Db = -0.21
no-mix: Db = -0.10
coupling enhanced for Db < 0  m < 0
->tt
much more stable
w.r.t. variation of m
bb(->bb)
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Search for 0(->tt)
D
Combination of three channels:
e+th , μ+th , e+m
Hadronic taus (th) identified with NN
“visible” mass
4-vec of visible t‘s decay prod.
MWe/m < 20 GeV
MTe/m < 10 GeV
to reduce W+jets bkg
HT < 70 GeV
to reduce tt bkg
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D
Search for 0(->tt)
Number of observed events consistent with
background => limits at 95% CL
Estimated using Mvis distribution for
subdivided samples:
- 3 types of t’s
- MWe/m < 6 GeV et 6 < MWe/m < 20 GeV
b(b)0(->bb)
and 0(->tt)
combined
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D
Search for b(b)0(->tt)
Look for: t(->μnmnt)+th
Hadronic tau (th)
identified with NN
At least 1 b-jet (JLIP)
|h| < 2.5 and ET > 15 GeV
no excess seen ...
even though B(->bb)/B(->tt) ~ 9
same sensitivity almost achieved
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Higgs bosons in the MSSM
D
In the process of combining the differents channels:
bbb(b) b(b)tt and tt
More input to consider in the long term
At the limit set by h-> tt for
mh=140 GeV, expect about 30
events from h->bb in Z->bb
analysis 
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D
Extra dimensions
D
Extra Dimensions: LED Model
n extra dims and SM fermions live on a D3-brane
Large Extra Dimensions (LED) Arkani-Hamed,Dimopoulos,Dvali Phys Lett B429 (98)
- MPL ~ 1019GeV
- n >= 2 compact and flat - MS : string/fundamental scale
M2PL ~ Rn MSn+2 => MS can be lowered to TeV scale
- gravitons propagate in the bulk => Kaluza-Klein tower G(k)
- can’t resolve successive modes
(0.01eV:n=2; 1MeV:n=3; 100MeV:n=6)
=> expect:
- virtual exchange of graviton KK modes
- real graviton emission
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D
LED: Virtual Graviton Exchange
dilepton channel SM
g/Z
_
f
G(n)
f
_
f
_
f
G(n)
f
f
SM
diphoton channel
G(n)
G(n)
s = sSM + hGsint + hG2sKK
Effect of ED parameterized by a single variable: hG = F/ MS4
different formalisms have different definitions of MS:
Hewett: (Hewett, Phys Rev Lett 82, 4765 (99) ) F=2l/p with l = ± 1
GRW: (Giudice, Rattazzi, Wells, hep-ph/9811291) F=1
HLZ: (Han, Lykken, Zhang, hep-ph/9811350) F=log(MS2/s) [n=2]; F=2/(n-2) [n>2]
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diEM
D
Large Extra Dimensions:
Virtual Graviton Exchange
diEM = combine ee and gg
2 EM objects, ET > 25 GeV
with track isolation
overall ID efficiency: 85 ± 1 %
CC-CC + CC-EC
for MdiEM > 350 GeV:
Nexp = 9.7 (1.6 QCD), Nobs = 8
Systematics: ~ 12%
signal for hG = 0.6
QCD
CC-CC + CC-EC
CC: |h|<1.1
CERN 12/09/06
200pb-1
D-Y+
direct gg +
QCD
EC: 1.5<|h|<2.4
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diEM
D
Large Extra Dimensions:
Virtual Graviton Exchange
200pb-1
Data agree with SM =>
MdiEM vs|cosq*| distrib.
used in 2D Binned Likelihood
=> Limits on hG
- alone
- combined with Run I
=> 95% CL limits on MS (TeV)
Most stringent constraints
on LED for n > 2 to date
among all experiments
Run II
Run I+II
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77
mm
D
•
2 m’s with PT > 15 GeV
o
o
o
•
•
Large Extra Dimensions:
Virtual Graviton Exchange
isolated, |h|<2.0
cosmic veto
Mmm > 50 GeV
for Mmm > 300 GeV:
Nexp = 6.4 and Nobs = 5
Systematics: ~ 13%
D0 RunII Preliminary
Mmmvs|cosq*| distr. used
in 2D Binned Likelihood
=> Set limits on hG
=> 95% CL limits on
MS (TeV)
250pb-1
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D
Extra Dimensions: RS Model
Warped Extra Dimension (RS)
Randull,Sundrum Phys Rev Lett 83 (99)
ED of size R, highly curved, compactified on S1/Z2 orbifold: y = R.
Zero mode graviton G(0) localized at the Planck-brane (y = 0)
SM fields localized on TeV-brane (y = Rp)
metric: ds2 = e-2kR hmndxmdxn – R2d2
k: curvature scale
for kR ~ 11-12, Lp = MPLe-kRp ~ TeV
consistency => 0.01 < k/MPL < 0.1
y=0
y=Rp
Gravitons propagate in the bulk =>
KK tower G(n) of modes of mass mn = xnke-kRp
(xn: 1st Bessel func. zeros i.e. 3.83, 7.02, 10.17, ...)
=> well separated modes
y
model characterized by mass m1 and coupling k/MPL
=> Look for first graviton resonance
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D
diEM RS Extra Dimension
SELECTION:
-2 isolated EM clusters
|h| < 1.1 (CC)
ET > 25 GeV
no track match equired (=> ee, gg)
QCD
D-Y+ direct gg + QCD
- QCD (instrumental) shape estimated from
data sample with EM obj. imcomp. with
electromagnetic showers
- MC and QCD relative contrib. fitted to data
in region 60 < Mee < 140 GeV
865 GeV
compare spectra for Mee > 140 GeV
agreement => ...
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Conclusions and Outlook
D
So far, no convincing hint of physics BSM at D0
But, substantially improved limits ...
... and we are still hopeful for discoveries 
Results presented were obtained with up to 1.1 fb-1
analyses being updated to full available luminosity
In the works:
LED in monojets + MET
LED, Z’, RS in ee, mm
Squarks and gluinos
Stop in tc,S topottom in bc
Leptoquarks
excited e*
RPV sneutrino in em
update and combine MSSM neutral Higgs analyses
SUSY H+ -> tn
Non Standard H -> tm
+ ...
... Stay tuned ...
More integrated luminosity is on its way with an improved detector...
design goal of 8 fb-1 likely to be achieved ...
=> Even more exciting years ahead
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