High p T Φ in jets
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High p T Φ in jets Select pairs of oppositely charged tracks provided: p T (Jet)>50Gev; (energetic jets); ∆R(Φ,Jet)<0.4 (tracks are assigned to the jet); x p ≣ T (K ± )/p T (jet)>0.1 (energetic tracks); N silicon >5 (good tracks); Χ/dof<2; (good fit); d 0 <1mm (coming from the interaction point); ∆Z 0 <5mm (same PI); ∑Q=0 (balanced charge); R p p ≣ T (track1)/p T (track2)<1.7 (balanced momentum). 0.17 good pairs/jet are selected
description
High p T Φ in jets. Select pairs of oppositely charged tracks provided: p T (Jet)>50Gev; ( energetic jets ); ∆R(Φ,Jet)0.1 ( energetic tracks ); N silicon >5 ( good tracks ); Χ/dof
Transcript of High p T Φ in jets
High pT Φ in jetsSelect pairs of oppositely charged tracks provided:
pT(Jet)>50Gev; (energetic jets);
∆R(Φ,Jet)<0.4 (tracks are assigned to the jet);
x ≣pT(K±)/pT(jet)>0.1 (energetic tracks);
Nsilicon>5 (good tracks);
Χ/dof<2; (good fit);
d0<1mm (coming from the interaction point);
∆Z0<5mm (same PI);
∑Q=0 (balanced charge);
Rp≣pT(track1)/pT(track2)<1.7 (balanced momentum).0.17 good pairs/jet are selected
High pT Φ in jets
Dmitry Milstein, Ohad Mamroud and E.D.
Results based on a first look at 30pb-1 of the data.
Naive K+K- mass distribution
K+K-
K+K+ / K-K-
Nice signal: How can we estimate the combinatorical background?
Naive K+K- mass distribution
1) Threshold disagreement2) ‘High’ mass disagreement
Removing π+π- which are consistent with originating in ρ0
decay
‘High’ mass problem solved!
Comparison with simulation
Threshold problem is not simulated!
Crude background subtruction
MC
Data
m(K+K-) m(K+K-)
Very nice narrow mass peak at mΦ.
η distribution of Φ candidates
η(Φ)
Reasonable agreement
comparing xΦ in MC and Data
No agreement!
XΦ
Transverse momentum spectrum
pT of Φ is well simulated
pT(Φ)
High pT Φ
pT(Φ)>50GeVpT(Φ)>60GeV
pT(Φ)>70GeV
pT(Φ)>80GeV
pT(Φ)>90GeV
See a signal even when pT(Φ)>100 GeV!
fit subtractionN(K+K−) = a1+a2∗mK+K− +a3/(mK+K− −a4)+a5∗exp(−
((mK+K− −a6)2/a7))
Di-Jet Event SelectionThe two leading jets contain most
of the transverse energy in the
event:
The two leading jets are in a back-
to-back configuration:
( jet1, jet2) > 3.0.
1 2
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0.95i
jetiT
jet jetT T
T jetTj p GeV
p pX
p
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Good Event / Bad Event Selection
The di-jet asymmetry is defined by:
good jets are defined as all jets in the
event in which YT < 0.1.
Bad jets, on the other hand, are found in
events in which YT > 0.3.
59% of the back-to-back di-jet events are
classified as good and only 0.9% as bad.
TE
Y 1 2
2 .Tjet jetT Tp p
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Position Dependence
We clearly see hot spots in which badly measured jets tend to hit.
Still need to look more carefully at the Dead OTX correction. 18
Charged Particle Association w/ Jets
The charged fraction carried by a jet
defined by:
A large amount of badly measured jets
have a high value of Rcharge.
We suggest cutting on Rcharge < 1.1 to
remove bad jets.
After this cut, the YT distribution looks
much nicer
( , ) 0.6charge
i
j
trackTj R track jet
jetT
pR
p
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Cutting on Rcharge < 1.1 removes 15% of the badly measured jets and barely
removes any well measured jets.
Charged Particle Association w/ Jets (2)
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