Transcript Heavy Quarkonia @ ATLAS

Prospect of Studying Direct J/Ψ
Production with ATLAS at the LHC.
E.Etzion, J. Ginzburg
Tel Aviv University
4th International Workshop on Heavy Quarkonia
Brookhaven National Laboratory, 27-30 June 2006
Outline
1. Heavy Quarkonia Production at the LHC
2. ATLAS
3. Generation with Pythia (NEW features!)
4. J/Psi selection
5. Polarization Measurement
7. Prospect
E. Etzion
Heavy Quarkonia 2006
2
• s = 14 TeV
LHC
pp
(7 times higher than Tevatron/Fermilab)
 search for new massive particles up to m ~ 5 TeV
• Ldesign = 1034 cm-2 s-1
(>102 higher than Tevatron/Fermilab)
 search for rare processes with small s (N = Ls )
ATLAS and CMS :
pp, general purpose
27 km ring used for
e+e- LEP machine
in 1989-2000
Start : Summer 2007
ALICE :
heavy ions
E. Etzion
LHCb :
pp, B-physics
Heavy Quarkonia 2006
3
Cross Sections and Production Rates
Rates for High luminosity
L = 1034 cm-2 s-1: (LHC)
• Inelastic proton-proton
reactions:
109 / s
• cc pairs
• bb pairs
•
•tt pairs
•Z  e e
8
/s
15 / s
• Higgs (150 GeV)
• Gluino, Squarks (1 TeV)
0.2 / s
0.03 / s
8 107 / s
5 106 / s
LHC is a factory for:
top-quarks, b-quarks, c-quarks, .Higgs, ……
(The challenge: you have to detect them !)
E. Etzion
Heavy Quarkonia 2006
4
Heavy Quarkonia Production at the LHC

The production rates for
heavy quark flavors at the
LHC will be huge

total cross-sections




c,b cross-sections



charm: 7.8 mb (7.81012 ev @ 1 fb-1)
bottom: 0.5 mb (0.51012 ev @ 1 fb-1)
top:
0.8 nb (0.8106 ev @ 1 fb-1)
equal for high pT in LO PQCD,
differences expected from NLO
(pT spectrum for c softer)
mass effects visible for low pT
Prediction of LHC rates by


tuning models with Tevatron data
extrapolating to LHC energies
E. Etzion
Heavy Quarkonia 2006
5
Various models in Quarkonium Production
• The Color Evaporation Model (CEM)
Assumes no correlation between the initial QQ
quarkonium state.
state and the final
• The Color Singlet Model (CSM)
Assumes each quarkonium state can only be produced by a QQ
same color and angular momentum state as that quarkonium.
pair in the
• The Nonrelativistic QCD Model (NRQCD)
Treats quarkonium as an approximately nonrelativistic system. When applied
to production, this implies that QQ pairs produced with one set of quantum
numbers can evolve into a quarkonium state with different quantum numbers,
by emitting low energy gluons.
E. Etzion
Heavy Quarkonia 2006
6
Heavy Quarkonia Production at the LHC II
LHC

The LHC will produce heavy quarkonia with high pT in
large numbers

assess importance of individual production mechanisms

E. Etzion
e.g. colour-singlet vs. colour-octet, factorisation
Heavy Quarkonia 2006
7
NRQCD
• NRQCD adds systematic nonrelativistic
corrections to effective field theory
using an expansion series in ν, (the
Two gluon fusion
a
velocity of the heavy quark in the
quarkonium rest frame).
• At high PT (PT >>mc) the dominant
process in NRQCD is the fragmentation
of a single gluon to a pair in a [8,3S1]
state (c). In comparison to the color
singlet fragmentation process in (b) this
occurs at a higher order of vc (vc7
versus vc3 ) but at a lower order of αs
(αs3 versus αs5).
• Taking into account these facts, it is
indeed plausible that the color octet
process could explain the observed
direct cross sections.
b
c
d
E. Etzion
Heavy Quarkonia 2006
8
Polarization Measurements at the Tevatron
heavy quarkonia polarization allows
for better discrimination between
different models of
e.g. NRQCD vs. colour-evaporation model
CDF RUN I
Recent measurements April 28, 2005
http://wwwcdf.fnal.gov/physics/new/bottom/050428.bless
ed-jpsi-polarization/
E. Etzion
Heavy Quarkonia 2006
9
ATLAS Detector
•
•
•
•
Inner Detector (ID)
Calorimeters
Muons Spectrometer
Magnetic system
• Tracking (||<2.5, B=2T) :
-- Si pixels and strips
-- Transition Radiation Detector (e/ separation)
• Calorimetry (||<5) :
-- EM : Pb-LAr
-- HAD: Fe/scintillator (central), Cu/W-LAr (fwd)
• Muon Spectrometer (||<2.7) :
air-core toroids with muon chambers
E. Etzion
Heavy Quarkonia 2006
Length : ~ 46 m
Radius : ~ 12 m
Weight : ~ 7000 tons
~ 108 electronic channels
~ 3000 km of cables
10
Inner Detector (ID)
Four sub-systems:
Pixels
(0.8 108 channels)
σφ=12 μm, σz=66 μm
Silicon Tracker (SCT)
5cm<radii<50cm (6 106 channels)
σφ=16 μm, σz=580 μm
Transition Radiation Tracker (TRT)
50<radii<100 cm (4 105 channels)
σ=170 μm per straw
The silicon detectors ~ 10
azimuthal position
measurements, 10 20μm
The TRT ~ 36 azimuthal
position measurements,
150 microns.
E. Etzion
Heavy Quarkonia 2006
11
Muon Spectrometer
The momentum of the muons is determined from the curvatures of their tracks in a
toroidal magnetic field.
Muon tracks are identified and measured after their passage through ~2m of material.
Track measurement with s=60m intrinsic resolution in three precision
measurement stations (MDT).
E. Etzion
Heavy Quarkonia 2006
12
Trigger & DAQ System
• LVL1 decision made:
– e, g, t, jet,  candidates
– Identifies Regions of Interest
• LVL2 uses Region of Interest
data
– Combines information from all
detectors
• Event Filter
– Can be “seeded” by LVL2 result
– potential full event access
E. Etzion
Heavy Quarkonia 2006
13
Muon Trigger System
• LVL-1 muon trigger: three trigger stations Resistive Plate Chambers (RPC) in the
barrel and Thin Gap Chambers (TGC) in the end-caps.
• Each station is made of 2 - 3 planes of strips / wires.
• A coincidence between a strip(or wire) hit in the 1st station and hits in the 2nd or 3nd
station.
• Low pt trigger: p > 6GeV
• High pt trigger: p > 20GeV.
IP
E. Etzion
Heavy Quarkonia 2006
14
g+g→J/Ψ +g Cross Sections
The prompt J/Ψ direct production using
3 different parton distribution functions.
CTEQ3L-Green
CTEQ5L-Red
CTEQ6M-Blue
 Trigger efficiency (low luminosity) for
pp→ J/Ψ → μ(6GeV)μ(3GeV) is ~10%
 Reconstruction algorithm efficiency ~60%
PT(GeV/c)
5 1032[bar 1 sec1 ] 1024[ particles / cm2 ] 108[bar ]  3.1107 [sec/ year ]  1.55 108[events / year ]
1.55 108[events / year]  0.1 0.6  9.3 106[events / year]
After one year we expect ~10 million events of pp→J/Ψ→μ-μ+
E. Etzion
Heavy Quarkonia 2006
15
Monte Carlo Study
• Generation with Pythia 6.221
• Parton distribution function - CTEQ6M
• The Octet model was implemented in Pythia 6.221
(adding two external differential cross-sections for
pp→J/Ψ +X corresponding colored 3S1 and 1S0 +3P0)
• Di-muon filter on PT greater than 3 and 6 GeV
applied in the event production.
• Geant-4 Simulation-> Digitization-> Reconstruction->
“My Analysis” algorithms.
• Currently moving to Pythia 6.326 version
E. Etzion
Heavy Quarkonia 2006
16
New Pythia versions
• Implementation of NRQCD native in the
new PYTHIA versions.
– Previously used as external routines.
– PYTHIA 6.326 enables a full charmonia and
bottomonia production (simultaneous
production of ψ’s and U’s, U(1S), U(2S)….
– The new PYTHIA code is under validation;
– Realistic parameter values (e.g. NRQCD
MEs) under studies.
• The standard code doesn’t contain complete
Heavy Quarkonia
2006
set of realistic default
parameters.
E. Etzion
17
Some Pythia settings
• Initial (61) and final (71) state radiation -shower
switched on.
• Pmas(4,1)=1.5 ( charm mass=1.5GeV)
• CTEQ6M parameters
• Ckin(3)=3 - kinematic cut
• BSignalFilter: muon PT1>6GeV, PT2>3GeV
• BSignalFilter: |Eta| cut <2.5
E. Etzion
Heavy Quarkonia 2006
18
The Pythia parameters of NRQCD effective matrix elements
Pythia
PARP(141)
ME
O H [ 2 S 1L(JC ) ]
O J / [ 3S1(1) ]
value
1.16
PARP(142)
O J / [ 3S1(8) ]
0.0119
PARP(143)
O J / [ 1S0(8) ]
0.01
PARP(144)
O J / [ 3 P0(8) ] / mc2
0.01
PARP(145)
O c 0 [ 3 P0(1) ] / mc2
0.05
PARP(146)
O  [ 3S1(1) ]
9.28
PARP(147)
O  [ 3S1(8) ]
0.15
PARP(148)
O  [ 1S0(8) ]
0.02
PARP(149)
PARP(150)
E. Etzion
O  [ 3 P0(8) ] / mb2
O b 0 [ 3 P0(1) ] / mb2
Based on
P. Nanson et al.,
“Bottom production”
HEP-PH/0003142
0.02
0.085
Heavy Quarkonia 2006
19
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Comparison of charmonium production
(LHC CM=14TeV)
All included subprocesses
421 g + g -> cc~[3S1(1)] + g
422 g + g -> cc~[3S1(8)] + g
423 g + g -> cc~[1S0(8)] + g
424 g + g -> cc~[3PJ(8)] + g
425 g + q -> q + cc~[3S1(8)]
426 g + q -> q + cc~[1S0(8)]
427 g + q -> q + cc~[3PJ(8)]
428 q + q~ -> g + cc~[3S1(8)]
429 q + q~ -> g + cc~[1S0(8)]
430 q + q~ -> g + cc~[3PJ(8)]
431 g + g -> cc~[3P0(1)] + g
432 g + g -> cc~[3P1(1)] + g
433 g + g -> cc~[3P2(1)] + g
434 q + g -> q + cc~[3P0(1)]
435 q + g -> q + cc~[3P1(1)]
436 q + g -> q + cc~[3P2(1)]
437 q + q~ -> g + cc~[3P0(1)]
438 q + q~ -> g + cc~[3P1(1)]
439 q + q~ -> g + cc~[3P2(1)]
E. Etzion
1.460E-01
5.415E-04
9.346E-03
3.082E-03
5.336E-03
2.316E-03
6.610E-04
1.143E-03
1.029E-05
0.000E+00
1.013E-06
2.729E-02
3.551E-02
3.837E-02
5.726E-03
7.982E-03
8.634E-03
0.000E+00
4.524E-06
3.118E-06
Pythia6.323(11.0.4)+External Color Octet
All included subprocesses: 1.560E-02 mb
86 g + g -> J/Psi + g ---- 5.957E-03 mb
87 g + g -> chi_0c + g-- 2.175E-03 mb
88 g + g -> chi_1c + g--- 4.161E-03 mb
89 g + g -> chi_2c + g ---3.304E-03 mb
Filter 0.6% of the events pass
di-muon filter with PT1>6GeV
and PT2>3GeV |eta|<2.5,old PYEVNT
model
BR(pp-Jpsi)=9.3E-03mb*0.006(m3m6)=55nb
Heavy Quarkonia 2006
20
Events Kinematics
Pythia versions:
6.326->Blue
6.221->Red (Rome Data)
PT Distributions
PT
Pseudorapidity
Events Multiplicity
EM
E. Etzion
Heavy Quarkonia 2006
21
First year of LHC at 900 GeV vs 14TeV
Pythia6.326 CMS=900GeV
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
All included subprocesses
421 g + g -> cc~[3S1(1)] + g
422 g + g -> cc~[3S1(8)] + g
423 g + g -> cc~[1S0(8)] + g
424 g + g -> cc~[3PJ(8)] + g
425 g + q -> q + cc~[3S1(8)]
426 g + q -> q + cc~[1S0(8)]
427 g + q -> q + cc~[3PJ(8)]
428 q + q~ -> g + cc~[3S1(8)]
429 q + q~ -> g + cc~[1S0(8)]
430 q + q~ -> g + cc~[3PJ(8)]
431 g + g -> cc~[3P0(1)] + g
432 g + g -> cc~[3P1(1)] + g
433 g + g -> cc~[3P2(1)] + g
434 q + g -> q + cc~[3P0(1)]
435 q + g -> q + cc~[3P1(1)]
436 q + g -> q + cc~[3P2(1)]
437 q + q~ -> g + cc~[3P0(1)]
438 q + q~ -> g + cc~[3P1(1)]
439 q + q~ -> g + cc~[3P2(1)]
E. Etzion
9.154E-03
5.540E-05
5.155E-04
1.915E-04
3.279E-04
1.809E-04
5.753E-05
1.004E-04
1.057E-06
0.000E+00
2.391E-24
1.663E-03
2.010E-03
2.186E-03
4.906E-04
6.539E-04
7.201E-04
4.278E-08
1.035E-06
1.538E-07
Pythia6.326 CMS=14TeV
All included subprocesses
1.460E-01
421 g + g -> cc~[3S1(1)] + g 5.415E-04
422 g + g -> cc~[3S1(8)] + g 9.346E-03
423 g + g -> cc~[1S0(8)] + g 3.082E-03
424 g + g -> cc~[3PJ(8)] + g 5.336E-03
Filter 5% of the events pass
di-muon filter with PT1>5GeV
and PT2>0.5GeV ,old PYEVNT model
BR(pp-Jpsi)=5.15E-04mb*0.05(m5m0.5)=26nb
Heavy Quarkonia 2006
22
Tunning Pythia: Multiple Interactions, new vs old models
•
•
Old model:ISR and FSR considered only for the hardest interaction. The
new model allows radiation to be associated with all the interactions. An
intermediate model implemented it in a disjoint matter where radiation
was associated in stages.
MSTP(81) : (D=1) master switch for multiple interactions (MI), and also
for the associated treatment of initial- and final-state showers and beam
remnants. Its meaning depends on whether PYEVNT (old and
intermediate models) or PYEVNW (new model) is called.
–
–
–
–
–
–
•
=0 : MI off; old model for PYEVNT, new model for PYEVNW.
=1 : MI on; old model for PYEVNT, new model for PYEVNW.
=10 : MI off; intermediate model for PYEVNT, new model for PYEVNW.
= 11 : MI on; intermediate model for PYEVNT, new model for PYEVNW.
= 20 : MI off; new model for PYEVNT or PYEVNW alike.
= 21 : MI on; new model for PYEVNT or PYEVNW alike.
Warning: many parameters have to be tuned differently for the old and new
scenarios, such as PARP(81) - PARP(84), PARP(89) and PARP(90), and
others are specific to each scenario. In addition, the optimal parameter values
depend on the choice of parton densities and so on. Therefore you must pick
a consistent set of values, rather than simply changing MSTP(81) by itself.
E. Etzion
Heavy Quarkonia 2006
23
Parametes settings going from PYEVNT to PYEVNW
E. Etzion
mstp(81)
1
21
New model, smooth ISR, high FSR
mstp(70)
-
2
New model, smooth ISR, high FSR
mstp(72)
-
2
New model, smooth ISR, high FSR
parp(82)
2.0
2.50
MPI cut-off parameter, PT0 and reconect
mstp(95)
-
1
PT0 and reconect
parp(78)
-
1.3
PT0 and reconect
mstp(82)
4
5
ExpOfPow(1.8) overlap profile
parp(83)
0.5
1.8
ExpOfPow(1.8) overlap profile
parp(89)
1800
1800
Reference energy & rescaling pace
parp(90)
0.25
0.25
Reference energy & rescaling pace
parj(81)
-
0.14
ΛESR scale
mstp(89)
-
1
Beam remnants
mstp(88)
-
0
Beam remnants
parp(79)
-
2.0
Beam remnants
parp(80)
-
0.01
Beam remnants
parp(67)
4
Not tuned
Parp(83)
0.5
1
Parameters of MSTP(82). The meaning depends on the
MSTP(82) setting. When MSTP(82)=5 needs numbers
between 1-2
parp(84)
0.4
1
like parp(83)
parp(85)
0.9
Not tuned
parp(86)
0.95
Not tuned
Heavy Quarkonia 2006
24
Kinematics with old and new model
Blue -> Old PYEVNT model
Red -> Intermediate PYEVNT model
Green -> New (not tuned) PYEVNW model
Currently under
study
E. Etzion
Heavy Quarkonia 2006
25
Selection of J/Ψ via Muon pair
(ATLAS GEANT4 full simulation)
• To properly select J/Ψ events, pairs of differently
charged muons are chosen.
Pt of the Lower Pt Muon
MeV
E. Etzion
Heavy Quarkonia 2006
26
J/Ψ mass reconstruction
• The selection is based on the di-muon
invariant mass reconstruction.
Gaussian Fit
Mean:3094.9
Sigma:42.9
Mass resolution σ(M2μ)=43MeV
E. Etzion
Heavy Quarkonia 2006
27
Background
• Where in the B-phys community the direct
J/Ψ is considered as background our main
contamination comes from ..
g+g→ B →J/Ψ+X .
• The cross-section for this process is :
σ(g+g→B →J/ Ψ→ μμ)≈10-2μb .
Signal / Background of O(1)
E. Etzion
Heavy Quarkonia 2006
28
bb̃ events rejection (proper-time cut)
The displacement of the two-track vertex from the beam line will be used to
distinguish between prompt J/Ψ or from B-hadron decays.
Log scale on axis
Y
N
pp→J/ Ψ+X
pp→ bb →J/ Ψ+X
N
ps
E. Etzion
Proper time Resolution 0.1 ps
ps
Heavy Quarkonia 2006
29
Efficiency and Purity of the proper-time cut
• Selecting events with proper time less than 0.3 ps
results in efficiency of 94% and contamination form
bb->J/Ψ at a level of 8%.
E. Etzion
Heavy Quarkonia 2006
30
Polarization Measurement Technique
•
•
Polarizations can be measured using the angular distribution of the daughter
particles produced in the particle decay.
The appropriate axis for defining a decay angle is the direction of the movement in
the pp centre-of-mass frame (which is also the ATLAS lab frame).
d
d cos  *
 1   cos 2  *
The polarization parameter α, defined
s  2s
as   s  2s ,
α =+1 transversely polarized
production, helicity ±1.
α =-1 longitudinal (helicity 0)
polarization.
α= 0 Unpolarized production consists
of helicity states +1, 0 and -1, and
corresponds to α= 0.
T
L
T
L
The decay angle is called θ* and is defined
to lie between the direction in the J/Ψ rest
frame and the J/Ψ direction in the lab frame.
E. Etzion
Heavy Quarkonia 2006
31
Polarization measurement
J/Ψ polarizations can be measured applying appropriate fit to
the angular distribution of the muons produced in its decay.
J/Psi Pt 3-9GeV
J/Psi Pt 9-16GeV
Cos(θ)
J/Psi Pt 16-25GeV
J/Psi Pt 25-40GeV
Cos(θ)
E. Etzion
Cos(θ)
Heavy Quarkonia 2006
Cos(θ)
32
Summary
•
•
•
•
•
•
•
•
•
•
•
CERN / LHC committed to deliver first collisions in 2007 (PP at CM=900GeV)
First Physics at 14 TeV is expected in 2008.
Important ATLAS milestones have been passed in the construction, pre-assembly,
integration and installation.
Major software and computing activities are underway as well, using (WLCG) for
distributed computing.
Commissioning and planning for the early physics has started
In the low luminosity runs direct J/Ψ will be one of the first ATLAS “B phys”
measurements.
This is one of the golden channels for the detector calibration and alignment.
ATLAS is still in the stage of validation and optimization of trigger and offline s/w
Currently study trigger and b-tagging effects
ATLAS B-physics trigger strategy rely on di-muon trigger for low luminosity when
there is spare processing capacity.
Beginning to exercise full analysis chain using events generated with recent Pythia
tuned MC
E. Etzion
Heavy Quarkonia 2006
33