CERN, 23 MARCH 2011
HECR OPEN ISSUES
M Nagano
New Journal of Physics 11 (2009) 065012
AGASA x 0.9
AUGER x 1.3
Difference in the energy
scale between different
experiments???
Different hadronic
interaction models give
different answers about
the composition of
HECR
The depth of the maximum
of the shower Xmax depends
on energy and type of the
primary particle
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
LHCF EXPERIMENTAL SET-UP
Detectors installed in the TAN region, 140 m away from ATLAS Interaction Point (IP1)
 Here the beam pipe splits in
2 separate tubes.
 Charged particle are swept
away by magnets
 We will cover |h|>8
Protons
Charged particles
Neutral particles
Front Counters: thin scintillators with 8x8cm2
acceptance installed in front of each main
detector
OSCAR ADRIANI
Beam pipe
LHCC MEET ING, CERN 23 MA RCH 2011
4 pairs of scintillating fiber
ARM1 & ARM2 DETECTORS
layers for tracking purpose
(6, 10, 32, 38 r.l.)
Impact point (h)
Arm#2
4 pairs of silicon microstrip layers
(6, 12, 30, 42 r.l.) for tracking
purpose (X and Y directions)
Absorber
22 tungsten layers 7– 14 mm
thick (2-4 r.l.) (W: X0 = 3.5mm,
RM = 9mm)
Arm#1
Energy
OSCAR ADRIANI
16 scintillator layers
(3 mm thick)
Trigger and energy
profile measurements
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
LHCF OPERATIONS @900 GEV & 7
TEV
th
th
With Stable Beam at 900 GeV Dec 6 – Dec 15 2009
With Stable Beam at 900 GeV May 2nd – May 27th 2010
Shower
Gamma
Hadron
Arm1
46,800
4,100
11,527
Arm2
66,700
6,158
26,094
With Stable Beam at 7 TeV March 30th - July 19th
We took data with and without 100 μrad crossing angle for
different vertical detector positions
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
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
DATA SET FOR INCLUSIVE PHOTON
SPECTRUM ANALYSIS
• Data
–Date : 15 May 2010 17:45-21:23 (Fill Number : 1104)
except runs during the luminosity scan.
–Luminosity : (6.5-6.3)x1028cm-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
PYTHIA8.145: about 107 pp inelastic collisions each
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
1 TEV p0 CANDIDATE EVENT
Longitudinal profile
A p0 candidate event
599GeV gamma-ray and
419GeV gamma-ray in
25mm and 32mm tower
respectively.
Transverse profile
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
LUMINOSITY ESTIMATION
Luminosity for the analysis is calculated from Front Counter
rates:
L = CF ´ RFC
The conversion factor CF is estimated from luminosity measured
during Van der Meer scan I1I2
LVDM = n b f rev
2ps xs y
VDM scan
Beam sizes sx and sy measured
directly by LHCf
BCNWG paper
https://lpc-afs.web.cern.ch/lpcafs/tmp/note1_v4_lines.pdf
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
Particle Identification
PID criteria based on transition curve
500 GeV <EREC<1 TeV
MC/Data comparison done
in many energy bins
•QGSJET2-gamma and -hadron are normalized to
data(/collision) independently
• LPM effects are switched on
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
PID CORRECTION
Efficiency and purity for gamma-ray estimated from L90%
fitting with MC template (QGSJET2).
Hatched : data
Red : true-gamma
Blue : true-hadron
Green : Red+Blue
Bin by bin (energy) correction
applied to take into account shape
disagreement between Data/MC
(see systematic error section)
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
p0 MASS
Arm1
Data
• Disagreement in the peak position
• No ‘hand made correction’ is applied for safety
• Main source of systematic error  see later
Peak at
145.8 ± 0.1 MeV
7.8 % shift
Many systematic checks have been done to
understand the energy scale difference
Arm2
Data
Peak at
140.0 ± 0.1 MeV
OSCAR ADRIANI
Arm2 MC
(QGSJET2)
Peak at
135.0 ± 0.2 MeV
3.8 % shift
LHCC MEET ING, CERN 23 MA RCH 2011
p0 MASS VS p0 ENERGY
Arm2 Data
No strong energy dependence
of reconstructed mass
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
h MASS
Arm2 detector, all runs with zero crossing angle
True h Mass:
547.9 MeV
MC Reconstructed h Mass peak: 548.5 ± 1.0 MeV
Data Reconstructed h Mass peak: 562.2 ± 1.8 MeV (2.6% shift)
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
MULTI-HIT REJECTION
In order to extract inclusive single gamma spectra, rejection of
multi-hit events is mandatory especially at high energy (> 2.5 TeV)
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
MULTI-HIT REJECTION
Multi-hit events are identified thanks to position sensitive layers
in ARM1 (SciFi) and Arm2 (Si-mstrip)
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
MULTI-HIT REJECTION
Single gamma
detection
efficiency for
various MC
models
Multi gamma
detection
efficiency for
various MC
models
Please have
a look to
systematic
error
section!
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
ACCEPTANCE CUT
We define in each tower a region common both to Arm1 and Arm2,
to compare the Arm1 and Arm2 reconstructed spectra.
Our final results will be two spectra, one for each acceptance region,
obtained by properly weighting the Arm1 and Arm2 spectra
R1 = 5mm
R2-1 = 35mm
R2-2 = 42mm
q = 20o
For Small Tower
h > 10.94
For Large Tower
8.81 < h < 8.99
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
ARM1 AND ARM2 COMPARISON
Multi-hit rejection and PID correction applied
Energy scale systematic not considered due to
strong correlation between Arm1 and Arm2
OSCAR ADRIANI
Deviation in small tower:
still unclear, but within
systematic errors
LHCC MEET ING, CERN 23 MA RCH 2011
COMBINED SPECTRA AND
COMPARISON WITH MODELS
Gray hatched:
stat.+syst. error
Blue hatched:
QGSJET2 stat.
error
Arm1 and Arm2
combined
spectra including
syst. errors
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
SYSTEMATIC UNCERTAINTIES
Uncorrelated uncertainties between ARM1 and ARM2
- Energy scale (except p0 error)
Estimated for Arm1 and Arm2
- Beam center position
by same methods but independently
- PID
Estimated by Arm2, and apply it to the both Arm
- Multi-hit selection
Correlated uncertainty
- Energy scale (p0 error)
- Luminosity error
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
SYSTEMATIC ERROR FROM ENERGY
SCALE
Two components:
- Relatively well known: Detector response, SPS => 3.5%
- Unknown: p0 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 p0 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.
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
BEAM CENTER POSITION
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
(Small tower, true single-gamma)
(Large tower, true single-gamma)
Fluctuation in HE is
probably statistical
100 GeV<E<3.5 TeV : 5%
OSCAR ADRIANI
100 GeV<E<2.5 TeV : 10%
E>2.5 TeV : 20%
LHCC MEET ING, CERN 23 MA RCH 2011
SYSTEMATIC ERROR FROM PID
Efficiency and purity are estimated with two different approaches
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:
100GeV<E<1.7TeV : 5%
1.7TeV<E : 20%
Both on small and large tower
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
SYSTEMATIC ERROR FROM MH
True/Reconstructed
True/Reconstructed
Systematic error is estimated from the deformation factor of original
MC spectrum wrt reconstructed MC spectrum for various models
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
CONCLUSIONS
• LHCf Inclusive photon analysis has been completed
• Many detailed systematic checks were necessary!
• ‘Very safe’ estimation of systematics
• First comparison of variuos hadronic interaction models with
experimental data in the most challenging phase space region
(8.81 < h < 8.99, h > 10.94)
• Other analysis are in progress (hadrons, PT distributions,
different h coverage etc.)
• We are upgrading the detectors to improve their radiation
hardness (GSO scintillators)
• Discussion are under way to come back in the TAN for the
possible p-Pb run in 2013 (LHCC, Alice, LHC, Atlas etc.)
• We will anyway come back for the 14 TeV run with upgraded
detector!!!!
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
A SPECIAL THOUGHT FOR JAPAN
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
OSCAR ADRIANI
LHCC MEET ING, CERN 2 3 MA RCH 2 011
IMPACT OF LHCF ON CR PHYSICS
Transition curve for 1017eV proton
π0 reconstructed spectrum
Xmax = 696.6g/cm2 ± 2.3 +15.9, -7.8 g/cm2
statistical systematic
⇔ΔXmax (DPMJETⅢ-QGSJETⅡ) = 36g/cm2
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
LUMINOSITY DURING THE VDM SCANS
26th April 2010
9th May 2010
Luminosity
(/cm2s)
FC1
5.90E+27
FC2
6.04E+27
FC1&2
5.99E+27
Luminosity
(/cm2s)
FC1
2.01E+28
FC2
2.00E+28
FC1&2
2.09E+28
Intensity information
Fill 1059 (26th April)
Fill 1089 (09th May)
beam1
8.98±0.34 N(1)
10.20±0.38
N(17851)
18.99±0.54 N(1)
19.08±0.54
N(17851)
beam2
10.35±0.37 N(1)
10.35±0.37 N(8911)
22.18±0.61 N(1)
21.21±0.59 N(8911)
beam1*2
92.94 N(1)
421.20 N(1)
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
LUMINOSITY ERRORS
contents
Intensity2
Difference between April scan & May scan
error
5.0%
2.1%
Difference between arm1&2
Total
2.7%
6.1%
Total systematic uncertainty due to luminosity was
estimated to be 6.1%
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
ESTIMATION OF PILE UP
When the circulated bunch is 1x1, the probability of N collisions per
Xing is
N
l exp[-l]
P(N) =
N!
L× s
l=
f rev
The ratio of the pile up event is
P(N ³ 2) 1- (1+ l )e- l
Rpileup =
=
-l
P(N ³1)
1- e
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
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
ENERGY RECONSTRUCTION AT SPS
Difference of energy reconstruction at SPS between data and MC is < 1%.
Systematic error for gain calibration factor layer by layer is 2%
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
COMPARISON OF EJ260 AND GSO
-PULSE SHAPE• Response for the N2 (Nitrogen) LASER
• pulse width is ~300ps （fast enough）
• EJ260 : ~12ns decay time
GSO
• GSO : 30~40ns decay time
• Roughly similar decay time
EJ260
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
COMPARISON OF EJ260 AND GSO
-RADIATION HARDNESS• EJ260 (HIMAC* Carbon beam)
10% decrease of light yield after
exposure of 100Gy
• GSO (HIMAC Carbon beam)
No decrease of light yield even after
7*10^5Gy exposure,
BUT increase of light yield is
confirmed
• The increase depend on irradiation
rate (~2.5%/[100Gy/hour])
*HIMAC : Heavy Ion Medical Accelerator in Chiba
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011
LINEARITY OF PMT R7400
• PMTs R7400 are used in current LHCf system
•
The test was held in HIMAC using Xe beam
• PMT R7400 showed good linearity within 1% up to signal
level corresponding to 6TeV showerMAX in LHCf.
OSCAR ADRIANI
LHCC MEET ING, CERN 23 MA RCH 2011