Commissione Nazionale Scientifica I
Pisa, 15-19 Settembre 2008
Status report
of the LHCf experiment:
preparation for data taking
Oscar Adriani
INFN Sezione di Firenze - Dipartimento di Fisica
dell’Università degli Studi di Firenze
LHCf: location and detector layout
Detector I
Tungsten
Scintillator
Scintillating fibers
Detector II
Tungsten
Scintillator
Silicon mstrips
INTERACTION POINT
IP1 (ATLAS)
140 m
140 m
Beam line
Detectors should measure energy and position of g
from p0 decays
e.m. calorimeters with
position sensitive layers
Two independent detectors on both side of IP1
 Redundancy
 Background rejection (especially beam-gas)
18 Settembre 2008
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O. Adriani
LHCf location
Detectors installed in the TAN region, 140 m
away from the Interaction Point, in front of
luminosity monitors
Here the beam pipe splits in 2
separate tubes.
Charged particle are swept
away by magnets!!!
We will cover up to y
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O. Adriani
Detector #1
2 towers 24 cm long
stacked vertically with 5
mm gap
Lower: 2 cm x 2 cm area
Upper: 4 cm x 4 cm area
Impact point (h)
4 pairs of scintillating
fiber layers for tracking
purpose (6, 10, 32, 38
r.l.)
Absorber
22 tungsten layers
7mm – 14 mm thick
(W: X0 = 3.5mm, RM = 9mm)
16 scintillator layers
(3 mm thick)
Energy
Trigger and energy
profile measurements
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Detector # 2
We used LHC style
electronics and readout
Impact point (h) 2 towers 24 cm long stacked
on their edges and offset
from one another
4 pairs of silicon microstrip layers
(6, 12, 30, 42 r.l.) for tracking
purpose (X and Y directions)
Lower: 2.5 cm x 2.5 cm
Upper: 3.2 cm x 3.2 cm
16 scintillator layers
(3 mm thick)
Trigger and energy
profile measurements
Energy
18 Settembre 2008
Absorber
22 tungsten layers
7mm – 14 mm thick (2-4 r.l.)
(W: X0 = 3.5mm, RM = 9mm)
CSN1 – Pisa
O. Adriani
Double ARM Detectors
Arm#2 Detector
Arm#1 Detector
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Installation
Final installation was completed in January 2008
No major problems have been found
Both Arm1 and Arm2 are working fine
No additional noise is found in the detectors, despite 200
m long power lines and signal cables (for the
scintillators)
 The only problem: quartz optical fiber for laser
calibration (yet another fiber problem…..)




– The quartz fiber for N2 laser calibration was broken last year
during installation
– The new fiber was installed in January … but….
– Problems in the connectors installation…. After this…..
– Unfortunately we discovered the fiber was the wrong one!!!!!!!!!!!!
– New and final installation in the last week free for access (May)
– Now is finally OK!
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CSN1 – Pisa
O. Adriani
Detectors in place
Installation performed in two phases:
1. Pre-Installation (2007)
Baking out of the beam pipe (200 °C)
2. Final Installation (Jan 2008)
LHCf
Luminosity
Monitor (BRAN)
ATLAS ZDC
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O. Adriani
Some problems of grounding have been solved….
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Counting room cables clean-up
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Front Counter
 2 fixed Front Counters
were installed in front
of Arm1 and Arm2
 They will not move with
Arm1 and Arm2
 They are segmented in
2 x and 2 y slices
 Very useful to check the
beam quality and
hence decide to move
Arm1 and Arm2 in the
operating position from
the ‘garage’ position
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O. Adriani
After the installation….
 After the installation was completed, a lot of work on:
– DAQ
• New VME board to increase DAQ rate up to > 1 KHz
• Integration of all the subsystem (Using MIDAS frame)
• Analyzer to check the data quality and online monitor
– Slow control software to control and monitor:
• Power supplies
• Manipulator
• Temperature monitor
– LHC interface
• New NIM style board (CIBU) to send ‘PERMIT’ to LHC (KILL the
beam in case of high rate)
• Handhshaking software signals (DIP standard) for Injection, Adjust
and Beam Dump
• LHCf Physics information (beam position, rate, background etc.)
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An Update on the 2007 SPS Beam Test
Test was very successful!!!!
 CERN : SPS T2 H4
Energy calibration of the
 August/September 2007
calorimeters
 Incident Particles
Spatial resolution of the
– Proton 150,350 GeV/c
tracking systems
– Electron 50, 100, 150, 200 GeV/c
Results were partially
– Muon 150 GeV/c
published on JINST:
2008 JINST 3 S08006
Setup
LHCf
Detector
Moving Table
18 Settembre 2008
Silicon
Tracker
Trigger
Scintillator
CSN1 – Pisa
O. Adriani
Monte Carlo
Energy Resolution
N Particles
Test Beam
Distance from Edge
Energy distribution is
corrected for leakage
MC predicts that the
leakage is energy independent!
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Energy Resolution
2 x 2 cm2 tower
2.5 x 2.5 cm2 tower
Energy resolution < 3% even
for the smallest tower!
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Simulation vs
Data
150 GeV m
Energy released in the
4° scintillation layer
100 GeV e-
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Simulation is very
well understood!
CSN1 – Pisa
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350 GeV Proton beam
p0 reconstruction
g
Not in scale!
g
Carbon target (3 cm)
in the slot used for beam monitor
9.15 m
Arm1
>107 proton on target (special setting from the SPS people)
Dedicated trigger on both towers of the calorimeter has been used
Calorimeters
Shower Profile @ First SciFi Layer
40mm
X
Egamma=18GeV
Y
20mm
Egamma=46GeV
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X
CSN1 – Pisa
Y
O. Adriani
p0 mass reconstruction
 250 p0 events triggered (in a quite big background) and on disk
(MeV)
 Main problems:
– low photon energy (≥ 20
GeV)
– Direct protons in the towers
18 Settembre 2008
Dm ~ 8 MeV
Dm/m ~ 6%
CSN1 – Pisa
O. Adriani
ARM1 Position resolution
sx=172 mm
σx[mm]
Number of event
200 GeV electrons
x-pos[mm]
sy=159 mm
σy[mm]
Number of event
E[GeV]
y-pos[mm]
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E[GeV]
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O. Adriani
ARM2 Position
Resolution
Position Resolution X Side
120
Data
100
Resolution (microns)
200 GeV electrons
sx=40 mm
Simulation Spread Out
80
60
40
20
0
0
50
100
150
200
250
Energy (GeV)
x-pos[mm]
Position Resolution Y Side
160
140
Data
Simulation Spread Out
Resolution (microns)
120
sy=64 mm
100
80
60
40
20
y-pos[mm]
Alignment has been taken into account
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0
0
CSN1 – Pisa
50
100
150
Energy (GeV)
200
250
O. Adriani
ARM2-Silicon Energy Resolution
200 GeV electrons
SPS beam test data
DE/E ~ 12%
Total energy measured in silicon (ADC)
By looking only at the silicon energy measured, we have an energy resolution ~ 10%!!!!!
We can use it as a check for the radiation damage of the scintillators
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Linearity in the Silicon Energy
Energy Linearity with Silicon Sensors
5,00E+03
4,50E+03
Data
Lineare (Data)
Energy Measured (a.u.)
4,00E+03
y = 24,927x - 596,44
R2 = 0,994
3,50E+03
3,00E+03
2,50E+03
2,00E+03
1,50E+03
1,00E+03
Correction for energy
leakage is not applied
5,00E+02
0,00E+00
0
50
100
150
200
250
Energy (GeV)
At least in the 50-200 GeV energy range the
silicon energy measurement is linear
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Preparation for data taking
 A ‘control room’ …. has been prepared since there was no
space for us in the Atlas buildings ….
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But our Control Room is fully equipped!
Furnitures
Telephones
Air conditioner
Network
Computers
Printers
……
And also with Japanese students!!!!!
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Dummy event
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Communications with LHC
LHCf sends signals to LHC through the DIP system.
forand
machine
tuning!
Link Important
have been tested
it works fine!
We are in strict contact with them.
 Experimental status (On/Off, Gain, etc.)
 Detector position (Garage/Operating, position in mm, etc.)
 Luminosity rate (Single and Double Arm)
–
–
–
–
Front Counter rate (single Arm, double Arm coincidence)
Small tower rate (single Arm)
Big tower rate (single Arm)
Double Arm coincidence rate (FC.AND.Towers in opposite sides)
 Horizontal and Vertical position of the Beam (every 10000 events or in
the whole RUN)
 Injection Inhibit
 Handshaking signals (Injection, Adjust, Beam Dump)
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We are ready for data taking
 On September 10 we observed some signals on Front
Counters, with Arm1 and Arm2 in garage position for
safety reasons
– That day the Atlas BPTX signal was still not available
(no info on the real bunches in the Atlas zone)
 On September 11 Atlas gave us the synchronized BPTX
signals, and we could take Front Counter data by using
this signal (still in garage position)
 We are measuring Beam-Gas from the Beam2 on Arm1
side
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‘Analysis’ of Beam Gas events
We got 116 FC triggers in 8.275.034 BPTX: Nt=116
2.109 protons/bunch
Total # of protons: Np=1.7 x 1016
We try to estimate the gas density r from this rate:
Nt=Np* L * s * r
L=effective lenght ~ 100 m
s=Cross section ~ 80 mbarn = 80 x 10-31 m2
We find: r = 8.5 x 1012 H/m3 = 4.2 x 1012 H2/m3
From the LHC Project Report #783: r = 1012 H2/m3
From the pressure measurement in April 2008: r ~ 1012 H2/m3
~ CONSISTENT!!!!!!!!!!!!!
18 Settembre 2008
CSN1 – Pisa
O. Adriani
While waiting for collisions….
Proton
A short comment on new
models:
PICCO, EPOS
Very big interest in LHCf data
and in this physics field
Drescher, Physical Review D77,
056003 (2008)
p0
Neutron
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LHCf : Monte Carlo discrimination
106 generated LHC interactions 
1 Minute exposure@1029 cm-2s-1 luminosity
Discrimination between various models
is feasible in a very short time
Quantitative
discrimination with
the help of a properly
defined c2
discriminating
variable based on the
spectrum shape
(see TDR for details)
5% Energy resolution
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O. Adriani
Conclusions
 A lot of work has been done in 2008
 Installation completed
 Preparation for running completed
 First beam gas events acquired
 Will we get collisions today???
 We are ready to send our info to LHC for beam
tuning
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Spare slides
Radiation Damage Studies
Scintillating fibers and scintillators
• Expected dose: 100 Gy/day at 1030 cm-2s-1
• Few months @ 1030 cm-2s-1: 10 kGy
• 50% light output
• Continous monitor and calibration with
Laser system!!!
30 kGy
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CSN1 – Pisa
O. Adriani
Estimate of the background
 beam-beam pipe
 E γ(signal) > 200 GeV, OK
background < 1%
 beam-gas
 It depends on the beam condition
background < 1% (under 10-10 Torr)
 beam halo-beam pipe
 It has been newly estimated from the beam loss rate
Background < 10% (conservative value)
18 Settembre 2008
CSN1 – Pisa
O. Adriani
Effect of LHCf on BRAN measurement
LUMI monitor (BRAN) inside TAN is beyond LHCf (replacing 4th copper bar)
IP1
Cu Bar / ZDC LHCf
LHCf Cu Bar / ZDC
Lumi
Lumi
The effect of LHCf on BRAN measurements
has been studied in the last months by
simulation
– Reduction of shower particles at BRAN
– Position dependence on beam displacement
(question from machine peoples: if we shift by 1
mm the real beam, does the center of the
measured neutral energy shifts by 1 mm?)
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O. Adriani
LHCf performances: p0 geometrical
acceptance
Arm #1
Arm #2
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LHCf performances: energy spectrum of p0
Typical energy resolution of g is 3 % at 1 TeV
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Transverse projection in TAN slot
ARM1: Maximization of the
acceptance for vertical beam
displacement (crossing
angle>0)
ARM2: Maximization of the
acceptance in R (distance
from beam center)
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LHCf: model dependence of
neutron energy distribution
Original n energy
18 Settembre 2008
30% energy resolution
CSN1 – Pisa
O. Adriani