The First Results from the LHCf experiment
and Cosmic-Ray Physics
Yasushi Muraki
Department of physics, Konan University, Kobe, Japan
On behalf of the LHCf collaboration
Contents
1. Experimental purposes
2. Experiment details
3. The first result of the highest energy photon spectrum
obtained by the highest energy accelerator
4. Impact on the cosmic-ray physics
Presentation @ CRIS2010, September 17th, 2010
The LHCf Collaboration
K.Fukatsu, Y.Itow, K.Kawade, T.Mase, K.Masuda,
Y.Matsubara, G.Mitsuka, K.Noda, T.Sako, K.Suzuki, K.Taki
Solar-Terrestrial Environment Laboratory, Nagoya University, Japan
K.Yoshida
Shibaura Institute of Technology, Japan
K.Kasahara, M.Nakai, Y.Shimizu, T.Suzuki, S.Torii
Waseda University, Japan
T.Tamura
Kanagawa University, Japan
Y.Muraki
Konan University, Japan
M.Haguenauer
Ecole Polytechnique, France
W.C.Turner
LBNL, Berkeley, USA
O.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi,
H.Menjo, P.Papini, S.Ricciarini, G.Castellini
INFN, Univ. di Firenze, Italy
A.Tricomi
INFN, Univ. di Catania, Italy
J.Velasco, A.Faus
IFIC, Centro Mixto CSIC-UVEG, Spain
D.Macina, A-L.Perrot CERN, Switzerland
preface
One of the main problems of cosmic-ray study is the energy determination.
Castagnoli method
Calorimeter method
Shower method
We have developed many techniques like
Transition radiation detector, NKG function, etc
Still it is a problem of the balloon flight to use a shallow depth
calorimeter, e.x., RUN-job, JACEE etc, fluctuation is sooo large.
Chudakov proposed to launch a satellite for fixing the mass composition
Problem at Moscow cosmic ray conference in 1987 to fix the problems
around the knee region. We have been called by Chdakov and assembled
in a room in the together with VIPS of Academician like Ginzburg.
But Soviet Union collapsed and this idea have never been realized.
1. The experimental Purpose
The main purpose of this experiment is to establish the production crosssection of pions at the very forward region in proton-proton interactions at
the highest energy region, using the highest energy accelerator in the world.
It has been dream of cosmic ray physicists for a long time.
To realize above purpose, we propose to install a compact calorimeter in
front of the beam intersection at 140m away.
It would be the smallest experiment using the largest accelerator in the world.
We require a rather low luminosity operation, say 1028 -1029 and rather small
bunches in a ring, say ~23 in a circle. ( In fact it was a few bunches)
By this experiment, we will be able to establish a very important data point,
which will be very useful to understand for not only the highest energy
cosmic ray problems, but also for establishing the forward code of the
GEANT 4 program.
@ 17th Rencontre de Blois, 5/16/2005 and LHCC
Experimental Purpose
Prepared by TOKO san in 2006
Present status : TA results appeared
Very good talks have been given in this conference
by B. Dawson and J. Matthews
The position of shower maximum
Knapp et al, Astroparticle Physics, 19(2003) 77
LHCf
UA7
Fe incidence
Why Very Forward?
The right side curve shows
when we measure only the
particles emitted into the
Feynman XF <0.05, we
only measure half of the
energy flow into the
showers. So the
measurement of the very
forward direction will be
very important.
xF<0.05
xF<0.1
Why forward? Why near the beam pipe?
To understand cosmic ray problems,
it is necessary to measure the differential cross-section
of the particles emitted into the very forward cone,
While accelerator people love to measure
heavy particles emitted at the central region θ≈ 90o
To realize this idea, we have proposed to install
a small calorimeters inside the small gap at 140m away
from the interaction point. In the region heavy iron
material, TAN is located in order to absorb strong
high-energy neutron beam produced by the pp collisions.
Technical Report on the CERN LHCf experiment
12 Oct. 2005
Measurement of Photons and Neutral Pions in the
Very Forward Region of LHC
O. Adriani(1), L. Bonechi(1), M. Bongi(1), R. D’Alessandro(1), D.A. Faus(2), M.
Haguenauer(3), Y. Itow (4), K. Kasahara(5), K. Masuda(4), Y. Matsubara(4), H.
Menjo(4), Y. Muraki(4), P. Papini(1), T. Sako(4), T. Tamura(6), S. Torii(7), A.
Tricomi(8), W.C. Turner(9), J. Velasco(2) , K. Yoshida(6)
1. Review of experimental purpose
2. The results of the test experiment
3. Trigger, Beam condition, Schedule, Concluding remarks
Y Chamber
Detector location
2. Experimental Details
Arm1 and Arm2 detectors
The calorimeters are composed of the tungsten material
with the total 44 radiation length , and 1.6 interaction mean free path.
4 layers are prepared for the identification of the shower center
by using either the scintillation fiber (Arm1) or the silicon strip detector (Arm2).
This guarantees not only the cross-check of the measurement but also
it makes possible the single diffractive events and double diffractive events.
To obtain the large acceptance ( PT range) to the photons , the calorimeter
can be lifted up and down by the remote manipulator.
Examples of simulated events for g and n
Configuration of the two calorimeters in the beam pipe
44 radiation length or 1.6 interaction mean free path
Detector vertical position and acceptance
Remotely changed by a manipulator( with accuracy
of 50 mm)
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 g from IP
7TeV collisions
L
Collisions with a crossing angle
lower the neutral flux center to
enlarge PT acceptance
N
Actual setup in IP1-TAN (side view)
BRAN-Sci
ZDC
type1
BRAN-IC
ZDC
type2
LHCf Front
Counter
Beam
pipe
Side view
TAN
Neutral
particles
IP1
Performance of the LHCf calorimeters
Energy resolution
≈ 2.8% @ 1TeV
Position resolution 160μm for Arm1 and 49 μm for Arm2
PMT response to the showers from 1 particle (muon) to
105 particles (induced by 1 TeV photon) (no saturation)
Particle Identification (PID) ( γ/n, quite well separated )
Leakage correction from the edge of the calorimeter tower
( confirmed by the SPS experiment). We only use the
showers that hit 2mm inside from the edge.
Actual data-taking
108 events =100Mevents
(1nb-1 ~ 108 collisions ~ 107 showers)
7TeV, without crossing angle, normal HV
Total number of events collected
Trigger pattern
Shower trigger
Two cal.@center
Showers in both
calorimeters
Arm1
50M
30M
20M
Arm2
55M
42M
25M
154M
138M
with crossing angle
shower trigger
Measured Spectra at 7TeV
Gamma-ray like
preliminary
Arm1Hadron like
preliminary
Gamma-ray like
preliminary
Arm2
Hadron like
preliminary
Very high statistics !! only 2% of all data
Comparisons with MC are on-going.
The energy spectrum of photons by
Arm1 and Arm2 detectors
Red : Arm1 Blue : Arm2: the same rapidity region has been chosen
only adjusted by the detection time
Energy scale is preliminary about±2%
7TeV results: Reconstruction of h
p0 Candidate
Preliminary
η Candidate
Another good energy calibration point.
Production yield of h much differs among the models.
p0 reconstruction
An example of
p0 events
25mm
measured energy spectrum @ Arm2
32mm
preliminary
Silicon strip-X view
Reconstructed mass @ Arm2
M/M=2.3%
• Pi0’s are a main source of electromagnetic
secondaries in high energy collisions.
• The mass peak is very useful to confirm the
detector performances and to estimate the
systematic error of energy scale.
preliminary
Examples of simulated events for g and n
The particle identification (PID)
between photons and neutrons
by Nakai
When we insist the efficiency to squeeze photons as constant,
hadrons will be involved at the highest energy region
When we make a criterion that the 90% energy of photons must be involved in
the 18 layers from the beginning, the rate of gamma-rays increases but the
catching efficiency of photons will go down. Neutrons will be involved.
The energy spectrum of photons at √s=7TeV
by different criterion of PID @ L=5.5×1028/cm2sec
However if we can make appropriate correction to
each criterion, we can reduce the photon spectrum.
Matters to be checked before publication
Linearity of photo-tubes (PMT) 
Leakage from the corner 
Energy resolution ( ~2%@1TeV) 
Particle identification 
Multi-hit correction
Beam-gas contamination(<0.1%?)
pile-up effect ( <0.7% depends on the luminosity)
Energy flow from the other calorimeter in multi-hit (5-7%)
Absolute energy calibration ( ±2%)
So still results are preliminary but things go to good direction.
The next target of the LHCf
The differential cross-section of photons at 7TeV
A promise from the LHCf
Until the time that we must submit our paper for the
proceeding, we will be able to fix several problems.
Details should be asked to Oscar Adriani (Firentze) or
Alessia Tricomi (Catania) a few weeks later.
The effect of our results to cosmic-ray physics
(a personal view 1)
Tibet AS array with Water (prospect)
The Ne-Nμ spectrum
Gamma/hadron separation
The effect of our results to cosmic-ray physics
(a personal view 2)
New data of TA and relation between Auger, Hi-Res and AGASA
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Acknowledgements We thank to the organizers
for a beautiful conference!
A brief history of the LHCf experiment
May. 2004
Oct. 2005
Feb. 2006
Jun. 2006
July 2007
Aug. 2007
Jan. 2008
Sep. 2008
Dec. 2009
Mar. 2010
July 2010
Letter of Intent
Technical report
Technical Design Report
LHCC approved
construction starts
SPS beam test
SPS installation
First beam at LHC
900 GeV run
7TeV run
Removal of the LHCf detector from IP1