1. Straw prototype test beam 2017: first glance at the data
V.O.Tikhomirov P.N.Lebedev Physical Institute of the Russian Academy of Sciences and National Research Nuclear University “MEPhI”
TRD test beam analysis meeting, CERN,

2. V.Tikhomirov. Straw prototype test beam 2017: first glance at the data
2017 test beam setup
Prototype with 4 mm straws and Xe- based gas mixture.
Each straw layer (column on the picture) was shifted in vertical direction with respect to each other to provide possible uniformity with respect to beam particles crossing the prototype.
Two or three straw in one layer were jointly connected to readout. Note: everywhere in the text below “straw number” really means “layer number”.
Different beams: 20 GeV mixed pions/electrons; 120 GeV, 180 GeV and 300 GeV muons
Three types of TR radiators were tested: polyethylene, mylar and polypropylene:
- PE: 125 mm foil / 3.3 mm gap
- mylar: 50 mm foil / 3 mm gap
PP: 62 mm foil / 2.2 mm gap,
30 foils in each of six radiator block.
For some beam particles (except of 300 GeV muons) a special configuration was also realized, when all 6 polypropylene blocks ware situated together in front of the prototype (“36_cm_PP”).
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

3. V.Tikhomirov. Straw prototype test beam 2017: first glance at the data
Pedestal trends
Fit QDC pedestals by Gaussian in +/-1/5σ around peak
Both calibration and physics runs are presented here (calibration runs are shown with enlarged markers)
Very stable: the individual straw variations during the whole test beam period on the average are 0.01%!!! for calibration runs and 0.25% for physics runs.
But: for some straws the physics run pedestals are shifted down compared to the calibration runs – probably, due to some pick-ups in electrical circuits. This effect, probably, have to be taken into account in final processing (is not done yet) -> ToDo list.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

4. V.Tikhomirov. Straw prototype test beam 2017: first glance at the data
Fe55 peak trends
Fit QDC Fe55 peaks by Gaussian in +/-1/5σ around peak
Normal gas pressure
High (1.45 bar) gas pressure
Rather stable: the individual straw variations during the whole test beam period on the average are 1.5%.
A special attention should be paid to few straws/calibration runs -> on the ToDo list
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

5. Ionization peak trends, pions & muons
Fit QDC ionization peaks by Landau function in keV region
Note: here and below dE/dx position values for high pressure runs are divided by factor BTW, the question: why these values are higher compared to normal pressure?
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

6. Ionization peak trends, 20 GeV pions
Here and below all values for physics runs are presented in two numbers: one (left on the plot) – if calibration is applied from nearest in time previous calibration run, another (right point) – calibration from nearest in time next calibration run.
For 20 GeV pions the individual straw variation of dE/dx peak position on the average is 3.8%.
But variance between different straws is much larger – 9.2%. The reason – non-uniformity of beam profile across straw’s diameters.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

7. Non-uniformity of beam profile
Evident four-multiplicity dependencies in number of hits (frequency) and in dE/dx peak position. This affects TR spectra too, of course. Not quite clear how it’s possible to take this effect into account…
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

8. Ionization peak trends, 20 GeV electrons
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

9. Ionization peak trends, 20 GeV electrons
Zoomed view for electrons in normal pressure runs.
For 20 GeV electrons the individual straw variation of dE/dx peak position on the average is 3.1%.
Spread between different straws is 9.5%, again – due to non-uniformity of beam profile across straw’s diameters.
Small variations depends of radiator type – due to influence of very soft part of TR spectra in dE/dx region.
Some straws show difference in the use of previous or next calibration runs. Problem should be solved in final processing -> ToDo list.
13-th straw (as you might expect ) here and in other runs is braked out and, possible, have to be excluded from the analysis.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

10. Ionization peak trends, 300 GeV muons
For 300 GeV muons the individual straw variation of dE/dx peak position on the average is 3.4%.
Spread between different straws is 9.1%.
No evident difference between runs with different radiator – due to small TR contamination in low-energy part of spectra.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

11. Ionization peak trends, 180 GeV muons
For 180 GeV muons the individual straw variation of dE/dx peak position on the average is 1.5%.
Spread between different straws is 8.7%.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

12. Ionization peak trends, 120 GeV muons
For 120 GeV muons the individual straw variation of dE/dx peak position on the average is 3.0%.
Spread between different straws is 12.0%.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

13. V.Tikhomirov. Straw prototype test beam 2017: first glance at the data
Spectra examples … …
Differential spectra (top) and probability to exceed energy (bottom) examples. 20 GeV electrons, polypropylene radiator. Evident rise of TR yield in straws layers just after radiator blocks: 1-st, 5-th etc.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

14. Probability to exceed 6 and 15 keV thrs, electrons
Evident influence of radiator type: polypropylene radiator manifests the higher TR yield, polyethylene – the lowest, mylar – in the middle. Run with all 6 polypropylene radiators installed in the front of the prototype (36_cm_PP) gives highest yield in first straw layers, and the lowest – in the last, as expected.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

15. γ-dependence of probabilities, polypropylene
Dependencies on Lorentz factor of probabilities to exceed 6 keV and 15 keV thresholds for each straw, polypropylene radiator. Factor ~2 of difference in probabilities for different straws for 6 keV thr and ~1.6 for 15 keV thr. So, it’s not evident – which straws (and how) should be used in analysis for best particle separation by γ factor.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

16. γ-dependence of probabilities, mylar
Dependencies on Lorentz factor of probabilities to exceed 6 keV and 15 keV thresholds for each straw, mylar radiator.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

17. γ-dependence of probabilities, polyethylene
Dependencies on Lorentz factor of probabilities to exceed 6 keV and 15 keV thresholds for each straw, polyethylene radiator. As the TR output is smaller compared to PP and mylar radiators, difference between straws is also smaller.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

18. γ-dependencies, radiators and straws comparison
Radiators comparison:
highest yield with polypropylene, when – mylar and lowest – polyethylene.
36 cm PP radiator in front of the
prototype demonstrates highest yield in first straw layers, but degradation in depth, as excepted.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

19. γ-dependence of number of straws, radiators comparison
Number of straws with energy deposition above thresholds: one (probably, the simplest) of possible criteria to distinguish particles with different Lorentz factors.
Polyethylene radiator shows biggest numbers, especially for 6 keV threshold.
But: mylar radiator demonstrates steeper dependencies in the region of γ above ~3∙103.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data

20. Future plans (ToDo list)
Finalize calibration procedure: take into account pedestal shifts in physics run; define how to use previous and next in time calibration runs; merge physics runs with the same conditions (beam, radiator).
Problem: how to take into account the influence of beam non-uniformity leading to difference in both dE/dx and TR spectra for different straw layers.
Look at the high-pressure data.
Develop and compare criteria for most efficient distinguish of γ factors (which thresholds, how many straw layers etc) or, possible, more sophisticated algorithms.
Toy MC: combine many radiator + straw four-layer blocks in one detector to see how efficiency of γ factor separation depends on total detector length.
Full MC (testbeam-2017 configuration description is almost ready): comparison with data, predictions.
V.Tikhomirov. Straw prototype test beam 2017: first glance at the data