Material budget, energy losses and multiple scattering.
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Transcript of Material budget, energy losses and multiple scattering.
![Page 1: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/1.jpg)
Material budget, energy losses and multiple scattering
![Page 2: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/2.jpg)
Barrel tracking
Momenta resolution for low momenta tracks determined mainly by energy losses and multiple scattering
Left side – momentum resolution for pion Right side - proton
![Page 3: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/3.jpg)
Energy loss between vertex and TPC
Left - rel. loss as a function of particle velocity Right – function of particle momenta
![Page 4: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/4.jpg)
Energy losses (Bethe Bloch)
-particle velocity material density Z - atomic number of absorber A – mass number of absorber I – mean excitation energy – density effect correction factor –
material dependent and dependent
2)1(
2ln
1/ 2
2
22
21
I
cm
A
ZkdxdE e
![Page 5: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/5.jpg)
Energy losses (Reconstruction)
- particle velocity material density K1 and K2 – Effective parameters
22
2
221 )1(ln
1/
kkdxdE
![Page 6: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/6.jpg)
Energy loses correction
Left side - correction shift as function of particle velocity
Right side – correction shift as function of particle momenta (pion)
![Page 7: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/7.jpg)
Energy loses correction
Left side - correction shift as function of particle momenta (kaon)
Right side – correction shift as function of particle momenta (proton)
![Page 8: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/8.jpg)
Multiple scattering (Gaussian approximation)
-particle velocity material density P - particle momenta
0
2
2 *6.13
X
x
cp
MeV
![Page 9: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/9.jpg)
Energy losses correction (Current) Material budget and radiation length
hardwired in the code Using symmetry of the detectors
Correction layer by layer during propagation Intervals in y and z in the local coordinate
frames Fast access Difficult to describe non symmetric parts
(big problem in TRD)
![Page 10: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/10.jpg)
Geo modeler (0) Used to get information necessary for
energy loss calculation and multiple scattering Local information - in each point density,
radiation length, Z, A defined (mean excitation energy missing)
Mean query time ~ 15 s Mean number of queries
~15 – between 2 ITS layer ~15 – between 2 TRD layers
![Page 11: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/11.jpg)
Geo modeler (1) Two option considered
1. Propagate track up to material boundary defined by modeler – get local material parameters
Time consuming - too many propagations 2. Calculate mean parameters between
start and end point <density>, <density*Z/A>, <radiation length> Faster (only one propagation), reusable in the
case of parallel hypothesis (ITS), not big changes in the tracking
![Page 12: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/12.jpg)
Implementation
AliKalmanTrack::MeanMaterialBudget(Double_t *start, Double_t *end, Double_t *param)
First test Track references in inner volume of
the TPC – propagated to the vertex
![Page 13: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/13.jpg)
TRD tracking
FollowProlongatioBackG implemented Using mean material budget 14 steps
Propagate to first plane Loop over TRD planes
Propagate and update in the sensitive layer Propagate to the next plane
Propagate to the outer volume of TRD
![Page 14: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/14.jpg)
Energy loss estimate resolution
Left side - old propagation Right side – new propagation
![Page 15: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/15.jpg)
Relative Pt resolution
Left side - old propagation Right side – new propagation
![Page 16: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/16.jpg)
Relative Pt resolution
Left side - old propagation Right side – new propagation
![Page 17: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/17.jpg)
Pt pulls
Left side - old propagation Right side – new propagation
![Page 18: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/18.jpg)
Time pulls
Left side - old propagation Right side – new propagation
![Page 19: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/19.jpg)
Conclusion First results in TRD tracking
Indication of improvements in the momentum and the time resolution
Test with propagation to the vertex using AliExternalParameter and GeoMedeler – better vertex position resolution Better interface required – without
user intervention
![Page 20: Material budget, energy losses and multiple scattering.](https://reader036.fdocuments.in/reader036/viewer/2022062408/56649efd5503460f94c10dec/html5/thumbnails/20.jpg)
Conclusion
Default access to the TGeoManager required Currently loaded by hand
Better energy loss parameterization- options: 1. Mean Energy loss and multiple
scattering calculation using TGeoManager
2. Tuning 1 free parameter -