Transcript Slide 1

CSN1
22 September 2011, Bari
LHCf: status and perspectives
Lorenzo Bonechi (INFN – Firenze)
on behalf of the LHCf Collaboration
Outline
• Overview of LHCf
– Cosmic rays in the atmosphere and hadronic interaction models
– Detection of neutral particles at low angle at LHC
– Description of detectors
• Data analysis
– Published results for single  in 7 TeV pp interactions
– On-going analysis for  at 7 TeV and single  at 900 GeV
• Simulation of p-Pb interactions
• Upgrade of detectors for new measurements
• Summary
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Purpose of the experiment
• Experimental measurement:
– Precise measurement of neutral particle (, 0 and n) spectra in the very
forward region at LHC
• 7 TeV + 7 TeV in the c.m. frame  1017 eV in the laboratory frame:
– We are simulating in the biggest’s world laboratory what happens in nature
when a Very High Energy Cosmic Ray interacts in the atmosphere
• Why in the very forward region?
– Because the dominant contribution to the energy flux in the atmospheric
shower development is carried on by the very forward produced particles
LHC
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The LHCf location
Recombination
Chamber
Detectors are
located Inside the
TANs (absorbers for
neutral particles)
Detectors measure energy and
impact point of  from 0 decays
e.m. calo tracking layers
Protons
Two independent detectors on both
sides of IP1
96mm
 Redundancy
 Background rejection (esp. beam-gas)
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Charged particles
Neutral
particles
Beam pipe
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Details of the detectors
Arm1
Sampling and imaging E.M. calorimeters
 Absorber: W (44 r.l , 1.55λI )
 Energy measurement: plastic scintillator tiles
 4 tracking layers for imaging:
XY-SciFi(Arm#1) and XY-Silicon strip(Arm#2)
 Each detector has two calorimeter towers,
which allow to reconstruct 0
Performances
Energy resolution (> 100GeV):
< 5% for photons and  30% for neutrons
Position resolution for photons:
< 200μm (Arm#1) and  40μm (Arm#2)
40mm
20mm
Arm2
32mm
Front Counters
• thin scintillators 80x80 mm
• monitoring of beam condition
•Van der Meer scan
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25mm
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Arm#2 Detector
Arm#1 Detector
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Summary of data taking 2009-2010
Data taking with Stable Beams at (450 + 450) GeV
•
•
Dec 6th – Dec 15th 2009 and May 2nd – May 27th 2010
42 hours for physics
Shower
Gamma
Hadron
Arm1
46,800
4,100
11,527
Arm2
66,700
6,158
26,094
Data taking with Stable Beams at (3.5 + 3.5) TeV
•
•
Mar 30th – Jul 19th 2010
150 hours for physics with different setups
•
Different vertical positions to increase the accessible kinematical range
•
Runs with or without 100 rad beam crossing angle
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Shower
Gamma
Hadron
Arm1
172,263,255
56,846,874
111,971,115
344,526
Arm2
160,587,306
52,993,810
104,381,748
676,157
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Analysis of (3.5+3.5) TeV data
• Clean sub-set of data (nominal config., no
beam crossing angle, low luminosity)


Distribution of L90%
Nominal config., no beam crossing angle
Low luminosity (measured by front counters)
• Particle IDentification

Study of longitudinal energy deposit (L90% is the
depth in calorimeter for containment of 90% of
the total released energy)
• Selection of single gamma events

Study of transverse energy deposit
• Energy reconstruction

Multiple hit event (seen
on one silicon layer)
Arm1
Arm2
Based on total energy deposit in scintillator tiles
• Common pseudo-rapidity region for Arm1/2

η>10.94 and 8.81<η<8.9
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Published results for single  at 7 TeV
Adriani et al., Physics Letters B 703 (2011) 128–134
(small tower)
(large tower)
DPMJET 3.04
SIBYLL 2.1
EPOS 1.99
PYTHIA 8.145
QGSJET II-03
Magenta
hatch: MC
Statistical
errors
Gray
hatch :
Systemati
c Errors
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Further analysis
s  7 TeV
- :
- Single  :
energy and pt (or ) distribution (in progress)
pt (or ) distribution
s  900 GeV
- :
no
- Single : energy and pt (or ) distribution (in progress)
Lower priority: hadrons (n)
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Neutral pions at 7 TeV
1(E1)
R
R
=
140 m
140m
2(E2)

I.P.1
M   E1E2
• 0’s are the main source of electromagnetic
secondaries in high energy collisions
• The mass peak is very useful to check the
detector performances and to estimate the
systematic error on the energy scale
Selected data (2010 May 15, 17:45-21:23, Fill# 1104)
No crossing angle, pile up is negligible (~0.2%)
Low luminosity : (6.3-6.5)x1028cm-2s-1
DAQ Live Time : 85.7% (Arm1), 67.0% (Arm2)
Integrated lumi : 0.68 nb-1 / 0.53nb-1 (Arm1/2)
MC simulations
DPMJET 3.04, QGSJET II-03, SYBILL 2.1, EPOS
1.99 and PYTHIA8.145
Propagation in beam pipe and detector response
are considered.
In each model 107 collisions are generated.
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25 mm tower
32 mm tower
Silicon -strip
X-view
Silicon -strip
Y-view
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Neutral pions at 7 TeV (Arm1) (2)
Type-I event
Type-II event
1
1
Large tower
Small tower
Large tower
2
2
Small tower
This has been dealt with so far.
It can cover wide opening angle.
Thus this type dominates in low
energy region.
While due to unavoidable gap
between each tower, sensitivity in
high energy is rather worse.
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Now it is possible to analyze this
type of events thanks to the
improvement of multi-hit
reconstruction.
Tight opening angle(~high E) can be
detected by this type of π0.
Mass peak is still wide.
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Neutral pions at 7 TeV (Arm1) (3)
LHCf-Arm1
Data 2010
(Large tower)
LHCf-Arm1
Data 2010
Blue solid : Total
Blue dashed : Signal
Cyan : BackGround
Yellow : Fitting error
No acceptance correction
No acceptance correction
For ref, values in DPMJET3
<Mγγ> = 135.2MeV
σ = 4.9MeV
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(Data-MC)/MC~7.8% (due mainly to energy scale)
Type-II has a peak around 135MeV, but BG reduction is
biggest homework
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Single photons at 900 GeV
This analysis is in a raw preliminary status for Arm1:
– Under development
– Energy reconstruction function is new
• special one for low energy region:
– PID threshold
• PID criteria is same as 7TeV
• Threshold is updated
– Multi-hit cut
– Not yet included (future plan)
– Systematic error
– Luminosity normalization
– All other corrections
For Arm2 we are generating Monte Carlo events (one month needed to
complete the generation for all models)
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Future measurements: proton – lead ion
The study of proton interactions with nuclei in the forward
region is important for cosmic ray physics, because strictly
related to the interactions of primary cosmic rays with the
atmosphere.
Ideally we would like to measure the interaction of protons
with Nitrogen ions (to reproduce real atmospheric showers)
or at least with light ions.
Anyway the study of proton – heavy ion interaction in the
forward region can be important to study the scaling
properties of cross sections with respect to the pp case ( nuclear
modification factors and parton density saturation)
Interaction  p-Pb @ LHC in 2012 (3.5 TeV protons).
We are studying the impact of our measurement.
LPCC @ CERN on 17 October 2011
(Hopefully in the near future also proton-light ion run will be
feasible, for example at RHIC!!!)
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proton – lead ion simulation
This simulation is based on the EPOS (version 1.99) interaction model
DPMJET III simulation is also under development
• Simulating protons with energy Ep = 3.5 TeV
– Energy per nucleon for ion is given by
EN 
Z
Ep
A
and results 1.38
TeV/nucl (at LHC the momentum must be the same for both beams)
• Arm2 geometry considered on both sides in this simulation
• Detector response not included yet
Right-side or
“p-remnant side”
Left-side or
“Pb-remnant side”
140 m
140 m
p-beam
Pb-beam
Beam line
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proton – lead ion: -ray hit map
Pb-remnant side
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p-remnant side
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proton – lead ion: neutron hit map
p-remnant side, E > 100 GeV
Only the proton remnant side is considered in
these plots, because on the ion-remnant side
a huge peak due to the neutron fragment is
found just coming along the beam line.
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p-remnant side, E > 500 GeV
E>100GeV
E>500GeV
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p – Pb: multiplicities on small tower
Pb –remnant side
p –remnant side
n
Too many neutron
fragments!!!

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p – Pb: multiplicities on big tower
Pb –remnant side
p –remnant side
n

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p – Pb: -ray pseudo rapidity distribution
Pseudo rapidity distribution
All energies
E>10GeV
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p – Pb: neutron pseudo rapidity distribution
All energies
E>10GeV
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p – Pb: energy vs pseudo-rapidity
PHOTONS
NEUTRONS
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p – Pb: energy spectra in p-remnant side
PHOTONS
SMALL TOWER
NEUTRONS
BIG TOWER
NEUTRONS
SMALL TOWER
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PHOTONS
BIG TOWER
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Upgrade of detectors
Rad-hard detectors are needed for operations at √s=14TeV
√s=7TeV operation in 2010
Dose ~ 200Gy
√s=14TeV operations
 10
Exp. Dose ~2000Gy
We replaces some parts to radiation harder hard ones
(no change to detector design)
Upgraded Detector
Current Detector
Plastic Scintillators（Eljen Technology EJ260）
Scintillating Fibers（KURARAY SCSF- 38）
Silicon Strip Detectors
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GSO scintillators
GSO scintillator bars
(use current ones)
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Radiation hardness: scintillators
Specification of both EJ-260(current detector)
and GSO(upgraded detector)
EJ-260
GSO
Radiation hardness (Gy)
100
106
Density (g/cm3)
1.02
6.71
X0 (cm)
14.2
1.38
Decay time (ns)
9.6
30-60
Light yield （NaI=100）
19.6
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GSO Scintillators
Test of GSO bar belts
1mmx1mm×20mmx5
*HIMAC : Heavy Ion Medical Accelerator in Chiba
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Relative Light Yield as a
function of dose.
The results have been
taken by irradiation of
carbon beam at HIMAC*
(290MeV/n)
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Upgrade of silicon detectors
SOME IMPORTANT POINTS UNDER INVESTIGATION :
1. Remove pedestal fluctuation (1nd level upgrade)
2. Reduce the saturation effect at E > 1 TeV (2nd level upgrade)
– Very important improvement for higher energy LHC runs
– It requires production of completely new silicon modules
3. Improve the energy resolution for the silicon system (2nd
level upgrade)
– Useful cross check for scintillators
1st level upgrade  before proton-lead run
2nd level upgrade  before pp at 14 TeV run
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Upgrade: pedestal fluctuation
1st level upgrade (minor intervention!)
To avoid pedestal fluctuation (observed also for low energy
photons) we will test soon some simple circuits to be installed
on the LV power lines to the front-end. Then we want to
decouple the powering of the two half-boards of each front-end.
Silicon modules are the
black ones in the picture.
This modification requires
opening the detector ,
cutting the power lines
and fixing some new
simple electric circuit.
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Upgrade: saturation effect
2nd level upgrade
To reduce the saturation effect for high energy releases in silicon
layers there are several possibilities that are under discussion
and investigation. Decision are not yet fixed. Main points are:
•
•
No possibility to change the Pace3 chips with higher dynamic range
preamplifiers
We should operate directly on the silicon side
1. Reducing the silicon depleted thickness to produce less charge
a. Decreasing the bias voltage (not safe)
b. Producing new thin silicon detectors (safer, but we loose the
possobility to detect MIPs)
2. Reducing the charge collected by the readout strips
a. Connecting the floating strips to ground (we save the sensitivity
to MIPs, but we loose probably in spatial resolution)
We are setting up a LASER system in laboratory for detailed tests
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Upgrade: saturation effect
2nd level upgrade
To reduce the saturation effect for high energy releases in silicon
layers there are several possibilities that are under discussion
and investigation. Decision are not yet fixed. Main points are:
•
•
No possibility to change the Pace3 chips with higher dynamic range
preamplifiers
We should operate directly on the silicon side
1. Reducing the silicon depleted thickness to produce less charge
a. Decreasing the bias voltage (not safe)
b. Producing new thin silicon detectors (safer but we loose the
possibility to detect MIPs)
2. Reducing the charge collected by the readout strips
a. Connecting the floating strips to ground (we save the sensitivity
to MIPs, but we have to study how much we loose in spatial
resolution)
We are setting up a LASER system in laboratory for detailed tests
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Upgrade: saturation effect (2)
The existing situation
Floating
Floating
Floating
Floating
Under investigation
GND
GND
GND
GND
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The charge collected on
the floating strip is
collected by capacitive
coupling on the read out
strip
The charge collected on
the grounded strip is
definitely lost!
We reduce the collected
charge.
We can also do more
complex geometries:
Readout-Gnd-Gnd
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Upgrade: saturation effect (3)
Silicon sensor
Fan-out circuits
Basic detection unit
Modifications:
New fan-out circuits
New bonding scheme
New thin silicon layers
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Upgrade: energy resolution
Our main idea:
• Do not increase the number of silicon layers
• Re-arrange the position of the existing 8 silicon layers inside
the calorimeter, to make better use of the 4 silicon sensors
currently located very deep in the calorimeter and not useful
for  energy measurement
• Keep anyway few ‘double layers’ to have a good matching
between x and y coordinates
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Upgrade: energy resolution (2)
Optimization of silicon layer positions for energy reconstruction
Silicon layer positions in the current Arm2 detector.
X,Y
X,Y
X,Y
X,Y
Distribute 8 silicon layers
X
Y
X
Y
X
Geometrical configuration of this simulation study
Y
X
Y
Silicon layers are inserted at the front of all scintillator layers.
For energy reconstruction, Summation of dE of all scintillator layers,
2, 8 and 16 of the 16 silicon layers.
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Upgrade: energy resolution (3)
Simulation implemented with the FLUKA simulation tool
Hit Position
Selection
8 Silicon Layers 6 6 12 12 18 26 34 42 X0
4<x<16,
4<y<16
Good energy resolution of the silicon layers !!
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2
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W
Scint
W
Silicon-X
W
Scint
W
W
Scint
W
Silicon-Y
W
22
21
20
19
18
17
16
15
W
Scint
14
13
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10
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8
7
6
5
4
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2
1
W
Scint
W
Silicon-X
W
Scint
W
Scint
W
Scint
Silicon-Y
W
Scint
W
Scint
W
Scint
Silicon-X
Silicon-Y
W
Scint
W
Scint
W
Scint
Slicon-X
Silicon-Y
W
Scint
W
Scint
W
Config 2: now no mechanical conflict, but different modularity starting from m
13
Config 1: now X-side silicon are correctly rotated, but modules 13 and 15 are
probably in conflict
Config 0: maybe better 2 silicon also after 12 R.L.; then not feasible because
layers must have G10 on the opposite side as IP
Upgrade: energy resolution (4)
Original configuration
(2X0 thick tiles)
double layers
Updated configuration
Summary
LHCf has published the single photon spectrum in two different pseudorapidity intervals in the very forward region of the LHC for 7 TeV total
energy pp interactions. New analysis are under development for the study
of neutrons and neutral pions and for the transverse momentum
distributions.
Plan for the future measurements:
1. Proton-lead run at LHC in 2012



Requires correction of pedestal fluctuation (test in lab with laser system)
Simulation under development (3.5 TeV proton energy)
Presentation of LOI at beginning of 2012
2. Proton-proton interactions at 14 TeV


It is the main purpose of this experiment
Reduction of saturation effect (test of possible solutions and production of
new silicon modules)
3. Study of a possible proton-light ion run at RHIC


Simulations under development
Visit at RHIC within end of 2011
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Backup slides
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The LHCf international collaboration
O.Adriania,b, L.Bonechia, M.Bongia, G.Castellinia,b, R. D’Alessandroa,b, A.Fausn,
K.Fukatsuc, M.Haguenauere, Y.Itowc,d, K.Kasaharaf, K. Kawadec, D.Macinag,
T.Masec, K.Masudac, Y. Matsubarac, H.Menjoa,d, G.Mitsukac, Y.Murakic,
M.Nakaif, K.Nodai, P.Papinia, A.-L.Perrotg, S.Ricciarinia, T.Sakoc,d, Y.Shimitsuf,
K.Suzukic, T.Suzukif, K.Takic, T.Tamurah, S.Toriif, A.Tricomii,j, W.C.Turnerk,
J.Velascom, A.Viciania, K.Yoshidal
a)
b)
c)
d)
INFN Section of Florence, Italy
University of Florence, Italy
Solar-Terrestrial Environment Laboratory, Nagoya University, Japan
Kobayashi Maskawa Institute for the Origin of Particles and the Universe, Nagoya University,
Nagoya, Japan
e) Ecole Polytechnique, Palaiseau, France
f) RISE, Waseda University, Japan
g) CERN, Switzerland
h) Kanagawa University, Japan
i) INFN Section of Catania, Italy
j) University of Catania, Italy
k) LBNL, Berkeley, California, USA
l) Shibaura Institute of Technology, Japan
m) IFIC, Centro Mixto CSIC-UVEG, Spain
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Open Issues on HECR spectrum
M Nagano
New Journal of Physics 11 (2009) 065012
Difference in the energy
scale between different
experiments???
40
Data set for photon analysis ([email protected]+3.5TeV)
• Data
– Date : 15 May 2010 17:45-21:23 (Fill Number : 1104)
except runs during the VdM luminosity scan.
– Luminosity : (6.3-6.5)1028cm-2s-1,
– DAQ Live Time : 85.7% for Arm1, 67.0% for Arm2
– Integrated Luminosity : 0.68 nb-1 for Arm1, 0.53nb-1 for
Arm2
– Number of triggers : 2,916,496 events for Arm1
3,072,691 events for Arm2
– Detectors in nominal positions and normal gain
• Monte Carlo
– QGSJET II-03, DPMJET 3.04, SYBILL 2.1, EPOS 1.99 and
PYTHIA 8.145: about 107 pp inelastic collisions each
41
Luminosity
• Luminosity for the analysis is calculated from Front Counter
rates:
FC
L  CF  R
• The conversion factor CF is estimated from luminosity measured
during VdM scan
LVDM = n b f rev
I1I2
2ps xs y
VDM scan
Beam sizes sx and sy measured
directly by LHCf
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Particle Identification (PID)
PID criteria based on transition curve
L90% variable is the depth at which 90% of
the signal has been released
MC/Data comparison done in
many energy bins
•QGSJET2-gamma and -hadron are normalized
to data(/collision) independently
• LPM effects are switched on
43
0 mass and energy scale issue (II)
Peak at
145.8 ± 0.1 MeV
Arm1
Data
7.8 % shift
• Disagreement in the peak position
 Peak at 145.8  0.1 MeV for ARM1 (7.8% shift)
 Peak at 140.0  0.1 MeV for ARM2 (3.8% shift)
• No ‘hand made correction’ is applied for safety
• Main source of systematic error  see later
Many systematic checks have been done to
understand the energy scale difference
Peak at
140.0 ± 0.1 MeV
Arm2
Data
Arm2 MC
(QGSJET2)
3.8 % shift
Peak at
135.0 ± 0.2 MeV
3.8 % shift
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Multiple hit (MHIT) event rejection (I)
•Rejection of MHIT events is mandatory especially at high energy (> 2.5 TeV)
One event with two hits in Arm2
One event with three hits in Arm2
MHIT events are identified thanks to
position sensitive layers in Arm1
(SciFi) and Arm2 (Si-strip)
45
Multiple hit (MHIT) event rejection (II)
Single  detection
efficiency for
various MC models
Multi  detection
efficiency for
various MC models
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Acceptance cut for combined Arm1/Arm2 analysis
For a comparison of the Arm1 and Arm2 reconstructed spectra we
define in each tower a region of pseudo-rapidity and interval of
azimuth angle that is common both to Arm1 and Arm2.
As first result we present two spectra, one for each acceptance region,
obtained by properly weighting the Arm1 and Arm2 spectra
R1 = 5mm
R2-1 = 35mm
R2-2 = 42mm
 = 20o
For Small Tower
 > 10.94
For Large Tower
8.81 <  < 8.99
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Comparison Arm1/Arm2
(small tower)
Multi-hit rejection and PID correction applied.
Energy scale systematic (correlated between
Arm1 and Arm2) has not been plotted to verify
the agreement between the two detectors within
the non correlated uncertainties.
(large tower)
Deviation in small tower is
still not clear. Anyway it is
within systematic errors.
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Summary of systematics (I)
• Uncorrelated uncertainties between ARM1 and ARM2
- Energy scale (except 0 shift) : 3.5%
- Beam center position : 1 mm
- PID : 5% for E<1.7TeV, 20% for E>1.7TeV
- Multi-hit selection :
•
Arm1 small tower: 1% for E<1TeV, 1%20% for E>1TeV
•
Arm1 large tower: 1% for E<2TeV, 1%30% for E>2TeV
•
Arm2 small tower: 0.2% for E<1.2TeV, 0.2%2.5% for E>1.2TeV
•
Arm2 large tower: 0.2% for E<1.2TeV, 0.2%4.8% for E>1.2TeV
Estimated for
Arm1 and Arm2
by same methods
but independently
• Correlated uncertainties
- Energy scale (0 shift): 7.8% for Arm1 and 3.8% for Arm2 (asymmetric)
- Luminosity : 6.1%
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Summary of systematics (II)
Beam center position
Multiple hit cut
`
`
Particle ID
`
More details in paper
Measurement of zero degree
single photon energy spectra for
√S=7TeV proton-proton
collisions at LHC
Submitted to Physics Letters B
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What do we expect from LHCf?
γ
π0
Energy spectra and transverse momentum
distribution of
•  (E>100GeV, DE/E<5%)
• Neutrons (E> few 100 GeV, DE/E30%)
• 0 (E>500GeV, DE/E<3%)
in the pseudo-rapidity range >8.4
n
51
Detector vertical position and acceptance
• Remotely changed by a manipulator( with accuracy
of 50 m)
Data taking mode
Viewed from IP
with different position
to cover PT gap
G
Distance from
neutral center
Beam pipe aperture
N
Neutral flux center
L
All  from IP
7TeV collisions
L
Collisions with a crossing angle
lower the neutral flux center thus
enlarging PT acceptance
N
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Linearity of PMTs (Hamamatsu R7400)
• PMTs R7400 are used in current LHCf system coupled to the
scintillator tiles
• Test of linarity was held at HIMAC using Xe beam
• PMT R7400 showed good linearity within 1% up to signal level
corresponding to 6TeV showerMAX in LHCf.
53
Accumulated events in 2010
108 events!
LHCf removal
54
Pile-up events
When the configuration of beams is 1x1 interacting bunches, the
probability of N collisions per crossing is
l exp[-l]
P(N) =
N!
N
The ratio of the pile up event is
L× s
l=
f rev
P(N ³ 2) 1- (1+ l )e- l
Rpileup =
=
P(N ³1)
1- e- l
The maximum luminosity per bunch during runs used for the analysis
is 2.3x1028cm-2s-1
So the probability of pile up is estimated to be 7.2% with σ of 71.5mb
Taking into account the calorimeter acceptance (~0.03) only 0.2% of
events have multi-hit due to pile-up. It does not affect our results
55
0 mass versus 0 energy
Arm2 Data
No strong energy dependence
of reconstructed mass
56
2 invariant mass and  mass
Arm2 detector: all runs with zero crossing angle
True  Mass:
547.9 MeV
MC Reconstructed  Mass peak:
548.5 ± 1.0 MeV
Data Reconstructed  Mass peak:
562.2 ± 1.8 MeV (2.6% shift)
0 candidate
 candidate
(50 events)
57
Analysis of events @ 900 GeV
Event sample
@ Arm1
Event sample
@ Arm2
58
Beam-gas backgroud @ 900 GeV
2009
2010
Very big reduction in the Beam Gas contribution!!!!
Beam gas  I, while interactions  I2
59
Beam test @ SPS
Detector
Energy Resolution
for electrons with 20mm cal.
- Electrons 50GeV/c – 200GeV/c
- Muons 150GeV/c
- Protons 150GeV/c, 350GeV/c
Position Resolution (Silicon)
Position Resolution (Scifi)
σ=172μm
for 200GeV
electrons
σ=40μm
for 200GeV
electrons
60
Energy reconstruction @ SPS
Difference of energy reconstruction at SPS between data and MC is < 1%.
Systematic error for gain calibration factor layer by layer is 2%
61
Particle and energy flow vs rapidity
Multiplicity@14TeV
Low multiplicity !!
Energy Flux @14TeV
High energy flux !!
simulated by DPMJET3
62
Radiation damage
Scintillating fibers and scintillators
• Expected dose: 100 Gy/day at 1030 cm-2s-1
• Fewmonths @ 1030 cm-2s-1: 10 kGy
• 50% light output
• Continous monitor and calibrationwith
Laser system!!!
1 kGy
30 kGy
63
Uncertainty on the energy scale
• Two components:
- Relatively well known: Detector response, SPS => 3.5%
- Unknown: 0 mass => 7.8%, 3.8% for Arm1 and Arm2.
• Please note:
•
- 3.5% is symmetric around measured energy
•
- 7.8% (3.8%) are asymmetric, because of the 0 mass shift
•
- No ‘hand made’ correction is applied up to now for safety
• Total uncertainty is
-9.8% / +1.8% for Arm1
-6.6% / +2.2% for Arm2
Systematic Uncertainty on Spectra is estimated from difference
between normal spectra and energy shifted spectra.
64
Uncertainty on the beam center
• Error of beam center position is estimated to be 1 mm from
comparison between our results and the BPM results
• The systematic errors on spectra were estimated from the difference
between spectra with 1 mm shift of acceptance cut area.
Arm1 Results - true single gamma events
100 GeV<E<3.5 TeV : 5%
5% to 20% linear rise from
100 GeV to 3.6 TeV
65
Uncertainty from PID
Efficiency and purity are estimated with two different approaches
Hatched : data
Red : true-gamma
Blue : true-hadron
Green : Red+Blue
Template fitting A:
Template fitting B:
1 degree of freedom:
3 degrees of freedom:
- Absolute normalization - Absolute normalization
- Shift of L90% distribution
- Width of L90% distribution
Hatched : data
Red : true-gamma
Blue : true-hadron
Green : Red+Blue
Arm1
Systematic error from PID are
assumed:
5% for 100GeV < E < 1.7TeV
20% for E > 1.7TeV
Both on small and large tower
66
Uncertainty from Multiple Hit corrections
ARM1
ARM2
67