searches for new phenomena with the d detector nick hadley the university of maryland
DESCRIPTION
Searches for New Phenomena With 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. - PowerPoint PPT PresentationTRANSCRIPT
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
N. Hadley PASCOS 2004
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%
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
AØ: The High Rise
BØ: CDF
CØ: Future BTeV
FØ: The RF
EØ: This Space For Rent
DØ:
N. Hadley PASCOS 2004
D Detector
• 2T Solenoid
• Silicon detector
• Fiber Tracker
• Upgraded Muon system
• Upgraded DAQ/trigger
N. Hadley PASCOS 2004
Integrated Luminosity
Integrated Luminosity more than doubled in the last 12 months
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
• 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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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.
N. Hadley PASCOS 2004
No excess seen
• No excess of di-lepton or di-photon events is seen. (Typical luminosities 200 pb-1)
• Set limits…
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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!
N. Hadley PASCOS 2004
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)
N. Hadley PASCOS 2004
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
N. Hadley PASCOS 2004
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)
N. Hadley PASCOS 2004
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)