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/19Flip Tanedo, No CHAMPS at DØ 1
CornellUniversity
/19Flip Tanedo, No CHAMPS at DØ
No CHAMPs at DØ
Flip Tanedo
2
7 December 2009Physics 7661, Fall 2009
Collider Physics
Presenting: 0809.4472
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
3
Kobe Bryant4x NBA CHAMPion2009 NBA Finals MVP2008 NBA MVP11x NBA All-Star2x scoring CHAMPion1997 Slam Dunk CHAMPion
Game-winning buzzer-beating 3-point shot last Friday against the Miami Heat. LAL 108, MIA 107.
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
• Long-Lived Charged Massive Particle
• Massive Metastable Charged Particle
• Heavy Stable Charged Particle
• Charged Massive Stable Particles
4
Experimentalist definition
Summary: charged shit that makes it out of the collider before decaying
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
• Approximately conserved quantum numbere.g. electron, proton
• Suppressed effective couplinge.g. muon (e.g. !"e#... man, I hate that process)
• Suppressed phase spacee.g. neutron (I know: not charged, STFU)
5
Standard Model examples
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
• GMSB: gravitino LSP, so NLSP may be chargede.g. third-generation sfermion (stau)
• AMSB: with M2 « M1 « M3, small splitting between $+ and $0
• Focus point CMSSM: M1,2 » !, degenerate Higgsino LSP and Higgsino-lke NLSP
• Split-SUSY: very large squark massmetastable gluino
6
Theorist’s definition
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
• Only consider electric charge
• Colored charges are a different story (R-hadron)
• Also assume CHAMPs are pair producedi.e. ignore cascade decays (for simplicity)
7
Collider definition
Let’s make some simplifying assumptions
Pair production: LEP gives a model-independent-ish M > 100 GeV bound from Z "(CHAMP)2
/19Flip Tanedo, No CHAMPS at DØ
WTF is a CHAMP
• Muon chamber hit with associated ECAL tracks
1. Large invariant mass (& high pT)
2. Slow velocity (time of flight measurement)
8
Collider definition
Time of flight? We can measure that?
Signature looks just like a heavy muon
/19Flip Tanedo, No CHAMPS at DØ
The Muon System
9
Fig. 44. Exploded view of the muon wire chambers.
Source: D0 Run II TDR, Nucl.Instrum.Meth.A565:463-537,2006; arXiv:physics/0507191
Different times of flight for particles at different polar angles are compensated for by varying cable lengths since the front-end electronics do not allow such timing adjustments.
/19Flip Tanedo, No CHAMPS at DØ
The Muon System
9
Fig. 44. Exploded view of the muon wire chambers.
Source: D0 Run II TDR, Nucl.Instrum.Meth.A565:463-537,2006; arXiv:physics/0507191
Different times of flight for particles at different polar angles are compensated for by varying cable lengths since the front-end electronics do not allow such timing adjustments.
/19Flip Tanedo, No CHAMPS at DØ
Cuts and BG• 2 “muons” with pT > 20 GeV
• At least one track is ‘collimated’ (ET, pT)Reducible BG: mesons
• Acolinear, outward moving muonsReducible BG: cosmic rays (very bad!)
• Sufficiently close to the beamlineReducible BG: Bs, beam halo, cosmic rays
• Irreducible BG: mismeasurements
10
/19Flip Tanedo, No CHAMPS at DØ
Background Simulation
• Randomly combine separate distributions of invariant mass and velocityCentral tracker is independent of muon chamber
• Velocity BG: ‘events’ invariant mass in Z peak: 70 - 110 GeV, passes other cutsThis is why the pair production assumption is useful
• Invariant mass BG: negative velocity events
• Subtle: modeling BG from the data itself. Chosing randomly from separate data sets gives us decorrelated background simulation.
11
/19Flip Tanedo, No CHAMPS at DØ
Data vs. Monte Carlo
12
(1! v)/!v
/19Flip Tanedo, No CHAMPS at DØ 13
Stau Mass [GeV]50 100 150 200 250
) [p
b]
- 1!"+ 1!"
# p
(p
$
-510
-410
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(a) -1DØ 1.1 fb
Charged Gaugino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1%
+ 1%
# p
(p
$
-310
-210
-110
1
10Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(b)-1DØ 1.1 fb
Charged Higgsino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1!
+ 1!
" p
(p
#
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(c) -1DØ 1.1 fb
M(GeV)60100200300
Signal4.70.70.10.004
BG30.9 ± 3.9
1.6 ± 0.8
1.7 ± 1.0
1.9 ± 0.7
Obs38113
e.g. Stau CHAMP
/19Flip Tanedo, No CHAMPS at DØ 13
Stau Mass [GeV]50 100 150 200 250
) [p
b]
- 1!"+ 1!"
# p
(p
$
-510
-410
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(a) -1DØ 1.1 fb
Charged Gaugino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1%
+ 1%
# p
(p
$
-310
-210
-110
1
10Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(b)-1DØ 1.1 fb
Charged Higgsino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1!
+ 1!
" p
(p
#
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(c) -1DØ 1.1 fb
M(GeV)60100200300
Signal4.70.70.10.004
BG30.9 ± 3.9
1.6 ± 0.8
1.7 ± 1.0
1.9 ± 0.7
Obs38113
e.g. Stau CHAMP
Above the blue line is excluded
Red line is the prediction for some arbitrary CHAMP model
This intersection is the lower bound on the CHAMP mass
/19Flip Tanedo, No CHAMPS at DØ 13
Stau Mass [GeV]50 100 150 200 250
) [p
b]
- 1!"+ 1!"
# p
(p
$
-510
-410
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(a) -1DØ 1.1 fb
Charged Gaugino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1%
+ 1%
# p
(p
$
-310
-210
-110
1
10Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(b)-1DØ 1.1 fb
Charged Higgsino Mass [GeV]50 100 150 200 250 300
) [p
b]
- 1!
+ 1!
" p
(p
#
-310
-210
-110
1
10
Observed Cross Section LimitExpected Cross Section Limit
NLO Cross Section PredictionNLO Cross Section Uncertainty
(c) -1DØ 1.1 fb
M(GeV)60100200300
Signal4.70.70.10.004
BG30.9 ± 3.9
1.6 ± 0.8
1.7 ± 1.0
1.9 ± 0.7
Obs38113
e.g. Stau CHAMP
M(GeV)60100200300
Signal4456550.2
BG23.6 ± 3.3
1.6 ± 0.8
1.9 ± 0.5
1.7 ± 0.6
Obs24112
e.g. Gaugino CHAMP
Above the blue line is excluded
Red line is the prediction for some arbitrary CHAMP model
This intersection is the lower bound on the CHAMP mass
/19Flip Tanedo, No CHAMPS at DØ
LHC?
14
Raklev, 0908.0315
In some regions, LHCb might be able to do better due to particle ID. E.g. medium-lived particles that decay inside the detector.
extr
a sli
de
/19Flip Tanedo, No CHAMPS at DØ
Bethe-Bloch
• Energy loss is almost independent of CHAMP mass
• So we can use the tracking system and treat CHAMP as !
• p measurement in central tracker +% measurement from ! system = m measurement
• But: software assumes %=1, track fit is poor for %<0.75Can treat % as an additional fit parameter, good to %>0.5
15
Raklev, 0908.0315
Signatures depend on interaction with detector
!"dE
dx# =
Kz2Z
A!2
!1
2ln
2mec2!2"2Tmax
I 2" !2 " #
2
"CHAMP charge Max possible KE transfer
CHAMP velocity
depends on %
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a sli
de
/19Flip Tanedo, No CHAMPS at DØ
Other CHAMPs
• UED with KK-parity
• RS with GUT-parity
• DSB (quantum numbers)
• Leptoquarks
• Additional generations
• Magnetic Monopoles
16
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a sli
de
/19Flip Tanedo, No CHAMPS at DØ
CHAMP Cosmology
• Hard to get a viable dark matter CHAMP
• Strong constraints from, e.g, BBN, CMB, ...CHAMP decay injects energetic particles into the plasma, abundance of light elements
• A CHAMP @ LHC would require model building to dilute its early universe density
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a sli
de
/19Flip Tanedo, No CHAMPS at DØ
Other Ideas
• Slepton trapping in water tanks Feng hep-ph/0405278 (colliders)Byrne hep-ph/020252 (cosmic rays)
• R-hadrons: CHAMPs + quarksInteractions with nuclei mainly due to quark. Can swap quarks, change electric charge.
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a sli
de
/19Flip Tanedo, No CHAMPS at DØ
Happy Winter Break!
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• DØ, 0809.4472• CDF note 8701• Fairbairn et al,
hep-ph/0611040• Raklev, 0908.0315• Feng & Smith,
hep-ph/0409278
References
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