1. Study of charm hadroproduction Tau neutrino production at CERN SPS
BEACH2018
The XIII International Conference on Beauty, Charm and Hyperon Hadrons
Peniche, Portugal
Study of charm hadroproduction
&
Tau neutrino production at CERN SPS
A.Murat GÜLER
METU Ankara
On behalf of the DsTau Collaboration
4/7/2019
A. Murat

2. Physics Motivations
Tau neutrinos are the least known particle in the Standard Model.
Testing the lepton universality in ντ CC cross section
ντ cross section was measured with a large uncertainty
Important for future neutrino experiments, SHiP, DUNE, Hyper-K..
4/7/2019
A. Murat

3. Concept of ντ Detection
Proton
beam τ ντ X
ντ production
ντ detection:
Statistical uncertainty 33% in DONUT. D+ Ds τ ντ X X'
Primary
proton
Main ντ source: Ds →  decays produced in proton interactions
 No experimental data on differential cross section of Ds
 Large systematic uncertainty (~50%) in the ντ flux prediction
4/7/2019
A. Murat

4. DONuT Experiment 9 ντ CC events observed ντ CC cross section
where n is the parameter controlling the longitudinal part of the Ds differential cross section
“Final tau-neutrino results from the DONuT experiment”, Physical Review D 78, 5 (2008)
longitudinal
dependence
transverse
dependence
4/7/2019
A. Murat

5. DsTau Experiment Emulsion based experiment @ CERN SPS
Precise mesurement of ντ CC cross section
Aiming to detect 103 Dsτ
Systematic uncertainties
DONuT
DsTau
Ds differential cross section (xF dependence)
~0.5
0.1
Charm production cross section
0.17
Decay branching ratio
0.23
Target atomic mass effects
(A dependence)
0.14
0.05
4/7/2019
A. Murat

6. Emulsion detectors Highest position resolution AgBr crystal
1014 crystals in a film
Highest position resolution
Emulsion film
Cross-sectional view
Emulsion layer (44 m)
Plastic base (200 m)
Emulsion layer (44 m)
200 nm
20 m
10GeV/c 
beam
Sensitivity 36 grains/100 m
3D tracking device
4/7/2019
A. Murat

7. High precision measurement
Intrinsic resolution of each grain = 50 nm
Two grains on top and bottom of 200 mm base  0.35 mrad
Discrimination of 2 mrad at 4σ level
A new system with piezo-based Z axis under development
Angular measurement reproducibility of 0.15 mrad was achieved
Piezo objective scanner
Position reproducibility ~ 8 nm
Angular reproducibility ~ 0.15 mrad θ
σx = 50nm
200 μm
base
Beam angle
4/7/2019
A. Murat

8. A pion Interaction in Emulsion
3D Vector information, position and slope .
Tracking by 35 nm position resolution.
m.i.p and nuclear fragment is easily distinguished

9. Detector Structure
400 ECCs will be exposed to accumulate 2.3x108 interactions
10 units
(total 100 emulsion films)
ECC for momentum measurement
(26 emulsion films interleaved with
1 mm thick lead plates)
Proton Ds τ X D+ X’
Tungsten / molybdenum
4/7/2019
A. Murat

10. Detection of Ds → τ → X event
Kink angle of Ds
The analysis chain: 1) Tag X decay (mean ~100 mrad) 2) Perform high precision measurement to detect Ds decay
<θ> 7 mrad
Need high precision measurement!
Flight length of Ds
<FL> = 3.3 mm
Flight length of τ
<FL>=2.0 mm
4/7/2019
A. Murat

11. Ds momentum reconstruction
Difficult to measure Ds momentum directly due to short lifetime
Artificial Neural Network (ANN) using 4 variables Ds τ
Primary proton
FLDs
FL τ
Δθ Ds → τ
FL: flight length
Δθ: kink angle
Δθ τ →X
Measure xFdistribution
Δp/p= 18%
Fit to (1-|xF|)n
n = 5.8
4/7/2019
A. Murat

12. Expected Performace
Relative systematic uncertainty for cross section measurement: ~30% with 2018 run  Re-evaluation of the DONUT result ~10% with run  Input for future measurement
2018 run
2021 run
Uncertainties
Aiming at 10% precision
to look for new physics effects in ντ -nucleon CC interactions
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A. Murat

13. DsTau Collaboration Status of the project Japan: Nagoya Kyusyu Aichi
Romania:
Bucharest
Russia:
Dubna
Turkey:
Ankara
Switzerland:
Bern
Japan:
Nagoya
Kyusyu
Aichi
Kobe
Letter of Intent Submitted to the CERN-SPSC in Feb. 2016
Test Beam Studies in November and May 2017
Physics runs : 2018,
4/7/2019
A. Murat

14. Beam Exposure schedule
Run
Beam time
Emulsion surface
Goal
2016 test beam
(10 modules)
Test of the setup
Proof of principle
2017 test beam
(~2 modules)
Improvement of exposure scheme
pilot run
(approved)
1 week
48 m2
(30 modules)
Test of large data taking and analysis
BG estimation with data
Physics results (~80 Ds →  detected)
2021 physics run
(recommended)
2 weeks
545 m2
(338 modules)
Physics results
(~1000 Ds →  detected)
2022 physics run
4/7/2019
A. Murat

15. Test Beam @ CERN H4 beam line
Target mover
ECC
Stage controled By each spill
Proton
Silicon detector
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A. Murat

16. Automatic Scanning Microscope
A fast scanning in Nagoya Univ.
Scanning speed of 22 m2/day
Precision measurement in Bern
Resolution ~0.3 mrad
Hyper Track Selector (HTS) System
2. Precision measurement to detect Ds  τ decay (a few mrad)
High speed scanning of full area to select τ  X + partner-charm decays (Δθ ~100 mrad)
4/7/2019
A. Murat

17. Automatic Scanning Microscope
~4000 tracks in 2 x 2 mm2, 15 films
1000 μm
4/7/2019
A. Murat

18. Efficiency of Ds detectionX qX
FLDs
FLt qt
Proton
MC with 400 GeV beam
Selection
Total efficiency (%)
(1) Flight length of Ds ≥ 2 emulsion layers 77
(2) Flight length of  ≥ 2 layers & Δθ(Ds) ≥ 2 mrad 43
(3) Flight length of Ds < 5 mm & flight length of  < 5 mm 31
(4) Δθ() ≥ 15mrad 28
(5) Pair charm: 0.1 mm < flight length < 5 mm
(charged decays with Δθ > 15 mrad or neutral decays) 20
4/7/2019
A. Murat

19. Z distribution of observed vertices Interactions in a tungsten plate
Event reconstruction
Measured proton beam density in the analyzed region: 4.36x105 beam tracks/3.61 cm2
Z distribution of observed vertices
Interactions in a tungsten plate
200 μm
# of vertices
Expected
1860
Observed
With parent 1832
Without parent 130
Tungsten
target
4/7/2019
A. Murat

20. Reconstructed Double vertex
Kink
IP of daughter μm
FL μm
kink angle 118 mrad
Vee
IP of daughters 20.9, μm
FL μm
opening angle 242 mrad
1000 μm
200 μm
4/7/2019
A. Murat

21. Double-decay topology event (open charm)
(Video in ppt)
Kink
IP of daughter μm
FL μm
kink angle 118 mrad
Vee
IP of daughters 20.9, μm
FL μm
opening angle 242 mrad
N1ry 40本以上
100 μm

22. Summary
The DsTau project is proposed to measure ντ production (Ds differential production cross section)
reduce systematic uncertainty in the cross section measurement to 10%
Emulsion detectors with nano-precision readout
About 1,000 Ds →  decays in 2.3×108 proton interactions will be detected.
By-product: study charm physics (~105 charm production)
Test experiments conducted in
Pilot run in 2018 and physics run from 2021
4/7/2019
A. Murat

23. Physics Motivations
Charmed hadron interaction cross section measurement D+ X
To be sure requesting daughter as electron D- X’ D+
4/7/2019
A. Murat

24. Physics Motivations Precise mesurement of in ντ CC cross section
reduce uncertainity to 10%
ντ : only the DONuT experiment
Measured as a function of a parameter n
describing dσ(Ds)/dxF ~(1-|xF|)n
No experimental data giving n for Ds
4/7/2019
A. Murat