3rd lhc detector alignment ws - cern, 16.06.09 andrea dainese 1 impact of misalignment on track and...
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3rd LHC Detector Alignment WS - CERN, Andrea Dainese 3 ALICE heavy flavour potential Combine electronic (| |TRANSCRIPT
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3rd LHC Detector Alignment WS - CERN, 16.06.09 Andrea Dainese 1
Impact of misalignment on track and heavy-flavour reconstruction
with the ALICE detector
Andrea DaineseINFN – Padova
for the ALICE Collaboration
3rd LHC Detector Alignment Workshop
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ContentsALICE heavy flavour program in a nutshellInner Tracking System alignment
impact on tracking resolutionresidual misalignment in view of results from cosmicsimpact on charm measurementimpact on beauty measurement
Muon spectrometer alignment and quarkoniaSummary
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ALICE heavy flavour potential Combine electronic (||<0.9), muonic (-4<<-2.5), hadronic (||<0.9) channels Cover central region (with precise vertexing) and forward region Cover also low-pt region (low x/X0 & low field 0.5T, OR forward )
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Heavy quarks as probes of the Quark-Gluon Plasma medium
A high-density QCD medium is expected to be formed in high-energy heavy-ion collisions deconfined Quark-Gluon PlasmaRHIC experiments have discovered jet quenching explore medium properties via its effect on calibrated probes (hard partons)
c,b: high masscolour triplet
gluon: mass=0colour octet
u,d,s: mass~0 colour triplet
QCD medium
Parton Energy Loss, mainly by medium-induced gluon radiation
QCD:
€
ΔE(εQGP ;CR ,m /E,L)
€
ΔEg > ΔE c≈q > ΔEb
Test mass dependence of QCD energy loss at LHC precise measurement of c and b hadrons pt distr. alignment of the Inner Tracking System (ITS)
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Quarkonia in Pb-Pb at LHC J/ dissociation (colour screening in a deconfined medium) &
regeneration (in-medium coalescence of charm quarks)?
30
enhanced suppression
enhanced regeneration
expected to dissociate only at LHC (hotter medium) Less tightly bound ’ expected to dissociate at same temp as J/
J/ anomalous suppressionat SPS and RHIC
medium energy density (GeV/fm3)
family separation is crucial di-lepton mass resolution alignment of the Muon Spectrometer () alignment of the ITS (ee)
SPS RHIC LHC?
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Inner Tracking System: target alignment precisions
Target Residual Misalignment: expected misalignment left after realignment, taken ~0.7resol. ~20% degradation of the resolution
SPD(r = 4 & 7 cm)
SDD(r = 14 & 24 cm)
SSD(r = 39 & 44 cm)
nom. resolutionsxloc zloc [m2] 11 100 35 25 20 830
residual mis. (shifts)xlocyloczloc [m3] 8 10 20 20 20 20 15 15 100
full mis. “20 m” (shifts)xlocyloczloc [m3]
random misal20 20 20 45 45 45 30 30 100
full mis. “30 m” (shifts)xlocyloczloc [m3]
random misal30 30 30 45 45 45 30 30 100
yloc
zloc
xlocdetector local c.s.: xloc~rglob, yloc~rglob, zloc = zglob
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Impact of ITS misalignmenton ITS+TPC tracking resolutions
effect of misalignment: large worsening factor 2 at high pt plus 5 m
effect of misalignmentonly above 10 GeV/c
Effect of misalignment on track impact parameter to the primary vertex (d0), pt, vertex resolutions studied
no misalmisal 10 mmisal 20 mmisal 30 m
no misalmisal 10 mmisal 20 mmisal 30 m
d0 resolution pt resolution
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Impact of ITS misalignmenton primary vertex resolution
Primary vertex reconstructed using tracks with ≥5/6 points in ITSSmall deterioration (10-20%) with random misalignments <20 mSignificant loss of resolution for high multiplicity events with misalignments >30 m
no misalmisal 10 mmisal 20 mmisal 30 m
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Alignment of the Inner Tracking Systemwith cosmics (Summer 2008)
100k events B=0Millepede alignment SPD+SSD (4 layers)Difficult to conclude on resolution (pt unknown)
But close to target of residual misalignment
2008 cosmic data, B=0
~ 30 m
track-to-track transverse distance at y=0 [cm]
/√2 ~ 21 m
ideal geometrytarget residual misalignment
ALICE Preliminary
S.Moretto
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ideal geometrytarget residual misalignment1 GeV
85m2 GeV52m
4 GeV37m
/√2
Alignment of the Inner Tracking Systemwith cosmics (prospects for Summer 2009)
ALICE plans to collect cosmics with B=±0.5T (and B=0) Study resolution VS pt
MC example:
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Impact on charm measurement:D0K
Main selection: displaced-vertex topologygood pointing of reconstructed D0 momentum to the primary vertex (cospointing 1)
pair of opposite-charge tracks with large impact parameters (product of the two impact parameters d0
K x d0 << 0)
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Impact on charm measurement:D0K
Main selection: displaced-vertex topologygood pointing of reconstructed D0 momentum to the primary vertex (cospointing 1)
pair of opposite-charge tracks with large impact parameters (product of the two impact parameters d0
K x d0 << 0)
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D0K Product of impact parameters
no misal misal 10 m
misal 20 m misal 30 m
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D0K: selection variables
Signal Background
Signal Background
Product ofimpact parameters,d0
K x d0
Cosine of pointing angle,cospoint
no misalmisal 10 mmisal 20 mmisal 30 m
no misalmisal 10 mmisal 20 mmisal 30 m
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D0K Effect on S/B and significance
Target residual misalignment (10 m): negligible effect30 m misalignment: 30% worsening of statistical errors
warning: this is much better than “no-realignment”
no misalmisal 10 mmisal 20 mmisal 30 m
no misalmisal 10 mmisal 20 mmisal 30 m
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Impact on beauty measurement:displaced single electrons method
Mesurement strategy:1) Electron PID (TPC+TRD): reject most of the hadrons2) d0 cut ~200 m: reduce charm and bkg electrons (Dalitz, conv.)
3) Subtract (small) residual background (ALICE data + MC)
PrimaryVertex B
electron
Xd0
rec. track
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Be+X: impact parameters (5<pt<7 GeV/c)
|d0| [m] |d0| [m]
no misal misal 30 m
Impact parameter distributions become broader with misalignment
negligible for target residual misal Shape charm and background approaches that of beauty for misaligment > 30 m
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Be+X: cross section errors vs pt
For a misalignment of 30 m in SPD, the performance at high pt (>10 GeV/c) deteriorates significantly statistical error on b signal systematic error from misidentified subtraction
For the target residual misalignment (<10 m in SPD), there is no deterioration of the performance
no misal misal 30 m
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Muon spectrometer alignment
Expected mounting precision (survey+photogrammetry):
chambers x,y,z ~ 1 mm detection elements x,y,z ~ 500 m
Alignment requirements: x, y < 50 mGeometrical Monitoring System:
chambers x,y,z ~ 20 mTrack-based alignment with Millepede:
J.CastilloTracking Chambers Tracking Chambers
Stations 1,2,3,4 and 5Stations 1,2,3,4 and 5
Slats typeSlats type
Quadrants typeQuadrants type
MC:pp, B=0
x: 20 m y: 20 m : 0.02 mrad
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Muon spectrometer alignment: pt resolution
Misalignment:X,Y=1000 mX,Y= 700 mX,Y= 500 mX,Y= 300 mX,Y= 100 mX,Y= 50 mX,Y= 0 m
Muons from
mounting precision
expected residual misalignment
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Muon spectrometer alignment:
Residual misal < 50 m needed
= 100 MeV/c2
Mass Sigma
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Muon spectrometer alignment: J/
Residual misal ~ 100 m seems satisfactory Residual misal ~ 50 m perfect
Mass Sigma
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SummaryHeavy flavour measurements have a central role in ALICE Physics program
heavy quark energy loss in high-density QCD matterquarkonia as a termometer of the QGP
Importance of detector alignmentInner Tracking System:
promising results from cosmics, target residual misal ~10 m seems realistic
< 5 m effect on track position resolution (d0)
negligible effect for benchmark channels D0K and Be+X30 m misalignment would deteriorate significantly the performance at high pt (important for energy loss study)
Forward muon spectrometer:<50 m residual misalignment needed to prevent worsening of mass resolution and to allow good separation of family
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EXTRA SLIDES
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ALICE heavy-flavour potential
ALICE combines electronic (||<0.9), muonic (-4<<-2.5), hadronic (||<0.9) channels
ALICE covers central and forward regions
Precise vertexing in the central region to identify D (c ~ 100-300 m) and B (c ~ 500 m) decaysALICE covers the low-pt region (B=0.5T)
ALICE(c/b)
ATLAS/CMS(b) LHCb
(b)
-2 0 2 4 61
10
100
1 year pp 14 TeV @ nominal lumin.
p Tof
Q-h
adro
n [G
eV]
of Q-hadron
ALICE(b)(c)
ALICE(c/b)
ATLAS/CMS(b) LHCb
(b)
-2 0 2 4 61
10
100
1 year pp 14 TeV @ nominal lumin.
p Tof
Q-h
adro
n [G
eV]
of Q-hadron
ALICE(b)(c)
HERA-LHC WorkshopCERN/LHCC 2005-014hep-ph/0601164
A.Dainese (ALICE)M.Smizanska (ATLAS)
C.Weiser (CMS)U.Uwer (LHCb)
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Inner Tracking System (ITS)Silicon Pixel Detector (SPD):• ~10M channels• 240 alignable vol. (60 ladders)
Silicon Drift Detector (SDD):• ~133k channels• 260 alignable vol. (36 ladders)
Silicon Strip Detector (SSD):• ~2.6M channels• 1698 alignable vol. (72 ladders)
SPDSSD
SDD
ITS total:2198 alignable sensitive volumes 13188 d.o.f.