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ATLAS??? SUSY

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Title: PowerPoint Presentation Last modified by: Created Date: 4/22/2009 7:24:48 PM Document presentation format: – PowerPoint PPT presentation

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Title: ATLAS??? SUSY


1
ATLAS???SUSYMissing Et
  • ?????????????????
  • ?????

2
SUSY
  • Spin?1/2????????????????

???????????????????????? http//www.icepp.s.u-tok
yo.ac.jp/asai/lhcwg/
3
Motivation
  • ????
  • GUT Scale(1016GeV)?EW Scale(102GeV)
    ?2??Scale????????
  • Fine tuning
  • radiative correction?Higgs??????
  • ????
  • SUSY??TeV???????GUT Scale?????
  • ??????
  • LSP??????????

LHC????????
4
SUSY?Background
Process Event rate at 21033 cm-2sec-1 ????? L10fb-1
QCD(multijets) HLT Triggered 40Hz 108
WJets(W?l?) 10Hz 108
ZJets(Z?ll) 1Hz 107
tt 1.6 Hz 107
bb PTgt10GeV 200 KHz (HLT 10Hz) 21012 (108 inc. di-m)
SUSY(1TeV) 20/h 5104
  • LHC??SUSY??????????
  • ???????????????????????????????????????

5
LHC??SUSY???
  • LHC?????????????? ?????????
  • ?????????????????cross section?
    ?????????(????????????)

6
SUSY?????
  • ?????????????????????
  • LSP( )?missing
  • SUSY???????????multijetsmissing Et
    (leptons)???????SUSY???
  • 0 lepton mode
  • Lepton?????? ??????
  • 1 lepton mode
  • High pt isolated e/µ?1??????

7
??????????
  • multijetmissingEt(leptons)???????????????
  • tt(w?leptonic decay mode)
  • s1nb
  • WNjets (W?l?)
  • s 10nb
  • ZNjets (Z?tt/Z? ??)
  • s 1nb
  • QCD(high Pt multijets)
  • s µb
  • SUSY
  • Min( )1TeV
  • s 1pb
  • Min( )1.5TeV
  • s 100fb
  • Min( )2TeV
  • s 10fb

SUSY????????????????????46????
8
??????????
g
Pythia?Herwig?? PS???
g
Top-pair Highest Pt of the additional jet
t
g
t
  • ????????(PS)???Pt?????????????under estimation
  • ???????????(ME)?Collinear?Soft????????
  • Collinear?Soft?????PS?????

ME
PS
Pt(GeV)
9
QCD Background
  • QCD?????????2??
  • Real missing
  • b,c?semileptonic decay ??????missing????
  • Fake missing
  • Energy?miss-measurement?missing???
  • QCD?s???????miss-measurement ????????????

D
l
?
Missing Et
B
Real missing
?
f
Fake missing
10
Matching
  • Alpgen?ME???
  • Pythia?Parton shower?????collinear?soft??????

Alpgen Pythia
  • Double Count??????Veto?????????
  • ME????parton??R0.7???????Jet????Veto
  • Matching?ttNjets,WNjets,ZNjets???

11
Matching 2
Z4jets??
phi
PS
  • ME parton
  • ? jet

Collinear? ????????
ME
Pt???? ????????
?
  • ME?4 jets???????parton shower???5 jets??????
  • ME?5jets?double count???veto??

12
0 lepton mode
  • ??????????10fb-1???
  • QCD?real missing??
  • SUSY????
  • No lepton
  • Missing Etgt100GeV
  • 4???????????Ptgt100GeV?Ptgt50GeV3?
  • Transverse Sphericity gt0.2
  • ??????????????????????????

QQjj
Count /400GeV/10fb-1
(GeV)
TDR Point 2
13
Jet energy vs. missing Et
  • High pt jet?SUSY?????????background???????? High
    pt jet?signal?background????????
  • Missing Et??????????background??????????

Pt of leading jet
QQjj
GeV
Missing Et
QQjj
GeV
14
1 lepton mode
  • SUSY????
  • 1 lepton
  • Missing Etgt100GeV
  • 4???????????Ptgt100GeV?Ptgt50GeV3?
  • Transverse Sphericity gt0.2
  • Transverse mass gt100GeV
  • QCD,Z ? ?????????????????
  • Lepton fake?study???

QQjj
Count /400GeV/10fb-1
(GeV)
15
Missing Et
  • Missing Et?SUSY?????????
  • ??????????????????????????
  • ??????????????????????????QCD????????????????????
    ???????????????
  • ???
  • Resolution????Gaussian?
  • Resolution????????????
  • Resolution??????????(Jet??Jet?Pt)?????

16
ATLAS?missing Et
  • Missing Et?????
  • ???????Cell??????weight??????(Cell base)
  • Muon?????????

Missing Et?resolution (TDR??)?
Missing Et resolution (A0?tt)
17
Fake missing Et (Full simulation)
  • fake Ex distribution ?????Non-Gaussian tail ???
  • QCD?s????????????????????????????

QCD sample fake missing Ex SEx200400GeV
Non-Gaussian Tail
fake Ex distribution
18
QCD BGMissing Et resolution
Crack??
Forward??
Crack barrel
Forward barrel
missEx miss-measurement (GeV)
missEx miss-measurement (GeV)
  • Full Simulation?????
  • Crack???????????????????????
  • Forward Calo?radiative hard??????resolution???
  • Crack?Forward?Jet????s??2?
  • ????????????

crack
forward
19
Topology dependence 1
Pt of leading Jet
SEt
Z3jets (Z?nn) Z6jets (Z?nn)
(GeV)
(GeV)
Missing Et?SEt????????????????rapidity????????????
??????Missing Et???????????????????? Z3jets?Z6j
ets?SEt???????? ????????????Z3jets?????Z6jets???
?
20
Topology dependence 2
missEx - missExTruth
Tail is somewhat different
Z3jets (Z?nn) Z6jets (Z?nn)
GeV
  • fake Ex distribution ???????( missEx
    missExTruth)
  • ?????????Z3jets????????????
  • ?????????????????

21
Summery of Contribution from the fake missing Et
No lepton mode SUSY signal Default s Default s x
2
Count /400GeV/10fb-1
jjjj BG
  • SUMMERY There are 3 topics
  • Non-Gaussian Tail
  • Resolution ? eta ??
  • Topology dependence
  • If resolution become worth by factor 2,BG
    increase significantly
  • SUSY signal ? fake missing BG.
  • QCD BG ???????
  • Missing Et resolution ? BG???????
  • ??????????resolution??????

(GeV)
22
Total BG
0 lepton mode
Count /400GeV/10fb-1
(GeV)
  • QCD real and fake missing. missing Et resolution
    ?default????tail ???????????
  • QCD BG (real fake missing ) ???background???????
    SUSY signal ? BG???????????

23
Another SUSY scale
0 lepton mode
(GeV)
(GeV)
24
??????
  • ME?????????????
  • PS???BG?????
  • 0 lepton mode???1 lepton mode????discovery
    potential???
  • Lepton fake?study???
  • ??
  • Missing Et?resolution???????
  • Crack,forward??
  • ????????????
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