Embed Size (px)
Citation preview
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Performance of the ATLAS RPC detector andLevel-1 muon barrel trigger at √s = 13 TeV
RPC2020 Workshop - Rome
Heng Lion behalf of the ATLAS Collaboration
University of Science and Technology of China
February 10, 2020
Heng (USTC) ATLAS RPC Performance February 10, 2020 1 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Outline
1 ATLAS Level-1 Muon Barrel trigger
2 ATLAS Resistive Plate Chambers
3 RPC detector performance
4 L1 Muon Barrel trigger performance
5 Upgrade studies for High-Luminosity LHC
6 Summary and conclusions
Heng (USTC) ATLAS RPC Performance February 10, 2020 2 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
ATLAS Level-1 Muon Barrel trigger⊛ ATLAS is a general purpose particle detector observing collisions at Large Hadron
Collider(LHC) at 40 MHz rate⊛ The Level-1 Muon Barrel trigger is one of the main elements of the online event selection
of the ATLAS experiment⊛ It exploits the Resistive Plate Chambers (RPC) detectors to generate the trigger signals⊛ The RPCs are placed in the barrel region of the ATLAS experiment: arranged in three
concentric doublet layers at radius 7 m, 8 m and 10 m, operating in a toroidal magneticfield of 0.5 ∼ 1 Tesla
⊛ The Level-1 Muon Barrel trigger allows to select muon candidates according to theirtransverse momentum → 3 low pT thresholds and 3 high pT thresholds
Heng (USTC) ATLAS Level-1 Muon Barrel trigger February 10, 2020 3 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
ATLAS Resistive Plate Chambers⊛ Parallel resistive (bakelite) plates are separated by 2 mm gas gap with insulating spacers⊛ Gas mixture of C2H2F4(94.7%, ionization gas), C4H10(5.0%, quencher gas) and
SF6(0.3%, electronegative gas) operated in safe avalanche mode applying a nominal HVof 9.6 kV
⊛ Orthogonal η and ϕ readout strips with 23-35 mm pitch⊛ ∼ 1 ns intrinsic time resolution → designed to identify proton bunches separated by 25 ns⊛ RPC detector chamber consists of 2 detector layers with 2 η and 2 ϕ readout panels⊛ RPC detectors cover the pseudo-rapidity range |η|<1.05 (θ < 38°) for a total surface of
about 4000 m2 and ∼ 3600 gas volumes (with 380k readout channels)
RPC detector single layer RPC detector doublet layer
Heng (USTC) ATLAS Resistive Plate Chambers February 10, 2020 4 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
RPC detector performance
Heng (USTC) Detector performance February 10, 2020 5 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
RPC detector response⊛ Measure RPC detector response with muons produced in pp collisions
− Muon candidates are reconstructed primarily withMDT detector and RPC ϕ coordinate readout
− Extrapolate muon tracks from MDT through magneticfield and material to RPC surface
− Muon induced ionization and avalanche → inducedsignal in RPC readout strips → hit is signal abovereadout threshold in one strip
Schematic view of the muon extrapolation to RPC surface
⊛ Measure hit position, time and multiplicityExpected muon η position minus
the closest η hit position
strips hits [mm]ηthe closest distance between muon track and 50− 40− 30− 20− 10− 0 10 20 30 40 50
muo
ns
100
200
300
400
500 PreliminaryATLAS
-1= 13 TeV, Run 358395, 0.72 fbsInclusive muons
side viewηOne RPC detector,
Online calibrated time of strip hitfor one example panel
reconstructed readout hit time T [ns]
100− 80− 60− 40− 20− 0 20 40 60 80 100
str
ips/
3.12
5ns
ηhi
ts fr
om
1000
2000
3000
4000
5000
6000
7000
8000
all hits
on track hits
fraction(|T| > 12.5 ns) = 0.021
fraction(|T| > 12.5 ns) = 0.003
PreliminaryATLAS -1= 13 TeV, Run 358395, 0.72 fbs
Inclusive muons side viewηOne RPC detector,
Hit multiplicity in response to muonpassage for one example panel
strips hit multiplicityη0 1 2 3 4 5 6 7 8 9 10
muo
ns
0
1000
2000
3000
4000
5000
6000
7000
8000
9000 all hits
inTime hits
signal hits
0.002± = 0.970all∈
0.002± = 0.967inTime∈
0.002± = 0.965signal∈
PreliminaryATLAS -1= 13 TeV, Run 358395, 0.72 fbs
Inclusive muons side viewηOne RPC detector,
⊛ Most of the panels perform properly with uniform position residual distribution in thewidth of a strip, negligible fraction of hits with time out of 1 BC and getting 1 or 2 hits inresponse to muon passage
Heng (USTC) Detector performance February 10, 2020 6 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
RPC detector efficiency - single chamber⊛ RPC detector efficiency is computed as the fraction of muons which are with hits
associated to the extrapolated muon track in RPC surface within a distance of 30 mmfrom the centre of the strip and within 12.5 ns from the triggered bunch crossing (BC0)
Detector efficiency measured with the hit multiplicityfor one example panel in one ATLAS run in 2018
strips hit multiplicityη0 1 2 3 4 5 6 7 8 9 10
muo
ns
0
1000
2000
3000
4000
5000
6000
7000
8000
9000 all hits
inTime hits
signal hits
0.002± = 0.970all∈
0.002± = 0.967inTime∈
0.002± = 0.965signal∈
PreliminaryATLAS -1= 13 TeV, Run 358395, 0.72 fbs
Inclusive muons side viewηOne RPC detector,
Detector efficiency for η and ϕ views, for each ATLAS runrecorded in 2018 → stable performance during the year
day/month in 2018
0.8
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
dete
ctor
effi
cien
cy07/05 28/05 18/06 09/07 30/07 20/08 10/09 01/10 22/10
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
One RPC detector|T| < 12.5 ns, |d| < 30 mm
viewη viewφ
⊛ The efficiency is over 96% in this panel with quite stable performance during the year
Heng (USTC) Detector performance February 10, 2020 7 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
RPC detector efficiency - overall system⊛ Most of chambers work with high efficiency⊛ Gap efficiency, defined by hits registered for at least one of η and ϕ coordinates overall is
∼ 94% on average⊛ The detector efficiency is stable around 90% during data taking in 2018 monitored using
60.8 fb−1 data
Distribution of the panel and gap efficienciesfor all alive panels in one ATLAS run in 2018
Efficiency0.5 0.6 0.7 0.8 0.9 1
Gap
s, D
etec
tors
/0.0
1
200
400
600
800
1000
1200
side viewηdetector
side viewφdetector
gap efficiency
PreliminaryATLAS = 13 TeV, Run 358395s
, Inclusive muons-10.72 fb
Mean 0.897
Mean 0.901
Mean 0.942
|T| < 12.5 ns, |d| < 30 mm
Mean detector efficiency for all alive RPC panels in each runrecorded in 2018 → stable overall performance during the year
day/month in 2018
0.82
0.83
0.84
0.85
0.86
0.87
0.88
0.89
0.9
0.91
0.92
mea
n de
tect
or e
ffici
ency
07/05 28/05 18/06 09/07 30/07 20/08 10/09 01/10 22/10
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
All live RPC detectors|T| < 12.5 ns, |d| < 30 mm
viewη viewφ
Heng (USTC) Detector performance February 10, 2020 8 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
L1 Muon Barrel trigger performance
Heng (USTC) Trigger performance February 10, 2020 9 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Trigger timing performance⊛ The RPC hits (muon signals) ”online” calibration is performed using programmable delays
in steps of 3.125 ns (1/8 BC)⊛ 99.6% - 99.7% of the Level-1 Muon barrel trigger hits are associated to the correct bunch
crossing with good stability during data taking period except a few outliers due to a triggertower losing synchronization during a run
⊛ Correct bunch crossing (BC) association is one of the main requirements of the Level-1Muon Barrel trigger and the RPC trigger is capable of satisfying the requirement
Global fraction of trigger hits per BC
L1 RPC trigger BC - Collision BC
2− 1.5− 1− 0.5− 0 0.5 1 1.5 2
Frac
tion
of e
vent
s / b
in
5−10
4−10
3−10
2−10
1−10
1
99.7
%
ATLAS Preliminary
Data 2015-1=13 TeV, 0.28 fbs
Fraction of trigger hits in correct BC for each run
day/month in 2018
0.988
0.989
0.99
0.991
0.992
0.993
0.994
0.995
0.996
0.997
0.998
0.999
Fra
ctio
n of
trig
ger
hits
in c
orre
ct B
C
07/05 28/05 18/06 09/07 30/07 20/08 10/09 01/10 22/10
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
thresholdsT
High p
Heng (USTC) Trigger performance February 10, 2020 10 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Trigger efficiency⊛ Trigger efficiency is one of the key parameters of the Level-1 Muon Barrel trigger⊛ It is measured using unbiased muons from Z→ µ±µ∓ candidates in each run⊛ Efficiency is limited in the barrel region by acceptance due to toroid support structures and
ATLAS ”feet” supports;
Trigger efficiency for offline muons as a functionof their transverse momentum
0 20 40 60 80 [GeV]
Toffline muon p
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
L1 m
uon
barr
el tr
igge
r ef
ficie
ncy
L1 MU4L1 MU6L1 MU10L1 MU11L1 MU20L1 MU21
ATLAS PreliminaryData 2018
-1 = 13 TeV, 60.8 fbsµµ→Z
|<1.05µη0.1<|
Plateau value of the trigger efficiency in each runrecorded in 2018
day/month in 2018
0.4
0.5
0.6
0.7
0.8
L1 m
uon
barr
el tr
igge
r ef
ficie
ncy
07/05 28/05 18/06 09/07 30/07 20/08 10/09 01/10 22/10
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
µµ→Z| < 1.05µη > 27 GeV, 0.1 < |
T
µp
L1 MU4L1 MU6L1 MU10L1 MU11L1 MU20L1 MU21
⊛ Efficiency × acceptance to detect muon candidates with pT > 20 GeV is ∼ 76.5% for lowpT thresholds and ∼ 70.0% for high pT thresholds with very good stability during the year
Heng (USTC) Trigger performance February 10, 2020 11 / 14
Plateau values:MU10 → 76.5%MU20 → 70.0%
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Upgrade studies for High-Luminosity LHC
Heng (USTC) Upgrade studies February 10, 2020 12 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Front End discriminator thresholds scan⊛ ATLAS RPC detectors are planned to operate until ∼ 2040⊛ At HL-LHC (L ∼ 7.5× 1034cm−2s−1) the integrated charge collected in the avalanche
will be enough high to limit the detector lifetime⊛ It is proposed to lower the HV in the RPC gas-gaps (9.6 kV → 9.2 kV). At the same time,
new RPCs will be installed in the innermost layer of the Muon Barrel Spectrometer toincrease the redundancy of the trigger system and the trigger efficiency
⊛ Study response of few RPC detectors at nominal and lower HV with different FE thresholds
high gain → efficiency increasing by ∼ 20%at HV = 9.2 kV from VFE = 1.0 V to 1.2 V
[V]FE
Front-End discriminator setting V
1 1.1 1.2
RP
C d
etec
tor
effic
ienc
y
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4HV = 9.6 kV
HV = 9.2 kV
ATLAS Preliminary
= 13 TeVs
side view, high gainηOne RPC detector,
FEThreshold decreases for increasing V
average gain → efficiency increasing by ∼ 10%at HV = 9.2 kV from VFE = 1.0 V to 1.2 V
[V]FE
Front-End discriminator setting V
1 1.1 1.2
RP
C d
etec
tor
effic
ienc
y
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4HV = 9.6 kV
HV = 9.2 kV
ATLAS Preliminary
= 13 TeVs
side view, average gainηOne RPC detector,
FEThreshold decreases for increasing V
⊛ Part of the efficiency lost by reducing the HV on RPC gas-gaps can be recovered bylowering the thresholds of the FE discriminator (10% on average)
Heng (USTC) Upgrade studies February 10, 2020 13 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Summary and conclusions
⊛ Muon barrel RPC triggers selecting muon candidates at 40 MHz collision rate are of crucialimportance for the ATLAS experiment
⊛ Many studies has been done to monitor the RPC performance continuously during the year⊛ ATLAS RPCs have been working with excellent performance (both detector and trigger)
since the completion of the system in 2008 even working at a instantaneous luminosity of afactor of 2 larger than the designed
⊛ Preliminary studies indicate that existing ATLAS RPCs will perform well at higherinstantaneous luminosity
⊛ Extra RPC chambers (BIS7/8) to install for Run 3 → See talk from Lorenzo Massa andextensive detector upgrades to prepare for High Luminosity LHC including new RPC innertriplet layer and new readout electronics → See talk from Yongjie Sun
Heng (USTC) Summary and conclusions February 10, 2020 14 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
back up
Heng (USTC) February 10, 2020 15 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
ATLAS Muon spectrometer⊛ 3D scheme of ATLAS Muon spectrometer⊛ R-Z view of the present (Run 1/2) ATLAS muon spectrometer layout. The green (blue)
chambers labelled BIS/BIL, BMS/BML, BOS/BOL, BEE (EIS/EIL, EES/EEL, EMS/EML,EOS/EOL) are MDT chambers in the barrel (endcap) regions of the spectrometer. TheTGCs, RPCs, and CSCs are shown in red, white, and yellow, respectively. Top: One of theazimuthal sectors that contain the barrel toroid coils (small sector)
TGCs
TGCs
Heng (USTC) February 10, 2020 16 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
ATLAS RPC parameters and performance
Heng (USTC) February 10, 2020 17 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
ATLAS data-taking performance during 2018
Heng (USTC) February 10, 2020 18 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
RPC detector response in one example ϕ panel
⊛ peak in the hit position plot is due to the bias from muon track ϕ coordinates measuredfrom RPC
Expected muon ϕ position minusthe closest ϕ hit position
strips hits [mm]φthe closest distance between muon track and 50− 40− 30− 20− 10− 0 10 20 30 40 50
muo
ns
100
200
300
400
500
600
700 PreliminaryATLAS
-1= 13 TeV, Run 358395, 0.72 fbsInclusive muons
side viewφOne RPC detector,
Online calibrated time of strip hitfor one example panel
reconstructed readout hit time T [ns]
100− 80− 60− 40− 20− 0 20 40 60 80 100
str
ips/
3.12
5ns
φhi
ts fr
om
1000
2000
3000
4000
5000
6000
7000
8000 all hits
on track hits
fraction(|T| > 12.5 ns) = 0.046
fraction(|T| > 12.5 ns) = 0.003
PreliminaryATLAS -1= 13 TeV, Run 358395, 0.72 fbs
Inclusive muons side viewφOne RPC detector,
Hit multiplicity in response to muonpassage for one example panel
strips hit multiplicityφ0 1 2 3 4 5 6 7 8 9 10
muo
ns
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
all hits
inTime hits
signal hits
0.002± = 0.972all∈
0.002± = 0.969inTime∈
0.002± = 0.960signal∈
PreliminaryATLAS -1= 13 TeV, Run 358395, 0.72 fbs
Inclusive muons side viewφOne RPC detector,
⊛ Most of the panels perform properly with uniform position residual distribution in thewidth of a strip, negligible fraction of hits with time out of 1 BC and getting 1 or 2 hits inresponse to muon passage
Heng (USTC) February 10, 2020 19 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Hit position reconstruction
⊛ Detector alignment and correct cabling are investigated using the correlation between theexpected and measured muon positions
strip impacted by extrapolated muon trackηIndex of 5 10 15 20 25 30 35 40
str
ip w
ith r
eado
ut s
igna
lη
Inde
x of
5
10
15
20
25
30
35
40
Muo
ns
1
10
210
-1= 13 TeV, 0.72 fbs Preliminary, Run 358395, ATLAS side viewη Inclusive muons, One RPC detector,
strip impacted by extrapolated muon trackφIndex of 5 10 15 20 25 30 35 40 45
str
ip w
ith r
eado
ut s
igna
lφ
Inde
x of
5
10
15
20
25
30
35
40
45
Muo
ns
1
10
210
-1= 13 TeV, 0.72 fbs Preliminary, Run 358395, ATLAS side viewφ Inclusive muons, One RPC detector,
Heng (USTC) February 10, 2020 20 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Trigger efficiency⊛ Trigger efficiency is measured using unbiased muons from Z boson decays(Z→ µµ
Tag&Probe)⊛ Efficiency limited in the barrel region by toroid support structures and ATLAS ”feet”
supports⊛ Further reduction due to gas-gaps disconnected from HV (gas leaks) → mostly located on
the external layer (BO chambers)
1− 0.5− 0 0.5 1ηoffline muon
0
0.2
0.4
0.6
0.8
1
L1 m
uon
barr
el tr
igge
r ef
ficie
ncy
L1 MU10
L1 MU20
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
> 25 GeVT
µ, pµµ→Z
2− 0 2 [rad]φoffline muon
0
0.2
0.4
0.6
0.8
1
L1 m
uon
barr
el tr
igge
r ef
ficie
ncy
L1 MU10
L1 MU20
ATLAS Preliminary-1 = 13 TeV, 60.8 fbsData 2018,
> 25 GeVT
µ, pµµ→Z
Heng (USTC) February 10, 2020 21 / 14
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
Gas gap current measurement⊛ RPC upper limit on gap current density is 30µA ·m−2 for HL-LHC⊛ Gas gap current (normalized to the gap area) as a function of instantaneous luminosity⊛ Aim to predict safe operating HV settings for each gas gap for HL-LHC⊛ Current proportional to the luminosity → this shows that the present RPC system is in a
very good status
]-1 s-2 cm30Instantaneous luminosity [10
10000 15000 20000
]-2
A m
µG
ap c
urre
nt d
ensi
ty [
0
2
4
6
8
10
12
14ATLAS Preliminary
=13 TeVsData 2018,
BML1A01
BML3A01
BML6A01
]-1 s-2 cm30Instantaneous luminosity [10
0 5000 10000 15000 20000
]-2
A m
µM
ean
gap
curr
ent d
ensi
ty [
0
2
4
6
8
10
12
14ATLAS Preliminary
=13 TeVsData 2018, BML1A01*DZ1
BML1A01*DZ2
BML3A01*DZ1
BML3A01*DZ2
BML6A01*DZ1
BML6A01*DZ2
Heng (USTC) February 10, 2020 22 / 14
