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
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
The LHCf Collaboration
preface
One of the main problems of cosmic-ray study is the energy determination.Castagnoli methodCalorimeter methodShower methodWe have developed many techniques like
Transition radiation detector, NKG function, etcStill 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 cross-section 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 maximumKnapp et al, Astroparticle Physics, 19(2003) 77
UA7
LHCf
Fe incidence
xF<0.05
xF<0.1The 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.
Why Very Forward?
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
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 purpose2. The results of the test experiment3. Trigger, Beam condition, Schedule, Concluding remarks
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.
Detector location
Y Chamber
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 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 m)
Distance from neutral center Beam pipe aperture
Data taking modewith different positionto cover PT gap
N
L
G
All from IP
Viewed from IP
Neutral flux center
N
L
7TeV collisions
Collisions with a crossing angle lower the neutral flux center to enlarge PT acceptance
Actual setup in IP1-TAN (side view)
LHCf Front Counter
LHCf Calorimeter
BRAN-IC
ZDC type1
IP1
ZDC type2
Beam pipe
TANNeutral particles
Side view
BRAN-Sci
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
Total number of events collected
Trigger pattern Arm1 Arm2
Shower trigger 50M 55M
Two cal.@center 30M 42M
Showers in both calorimeters
20M 25M
with crossing angle
7TeV, without crossing angle, normal HV
shower trigger 154M 138M
(1nb-1 ~ 108 collisions ~ 107 showers)
Measured Spectra at 7TeV
preliminary preliminary
Gamma-ray likeGamma-ray likeHadron likeHadron like
Arm2Arm2
preliminarypreliminaryGamma-ray likeGamma-ray like Hadron likeHadron likeArm1Arm1
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
0 Candidate
η Candidate
Another good energy calibration point.Production yield of much differs among the models.
Preliminary
0 reconstruction
ΔM/M=2.3%
Reconstructed mass @ Arm2
measured energy spectrum @ Arm2
preliminary
preliminary
An example of 0 events
• 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.
25mm 32mm
Silicon strip-X view
Examples of simulated events for 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 correctionBeam-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
PreliminaryPreliminary
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Acknowledgements We thank to the organizers for a beautiful conference!
A brief history of the LHCf experiment
May. 2004 Letter of Intent
Oct. 2005 Technical report
Feb. 2006 Technical Design Report
Jun. 2006 LHCC approved
July 2007 construction starts
Aug. 2007 SPS beam test
Jan. 2008 SPS installation
Sep. 2008 First beam at LHC
Dec. 2009 900 GeV run
Mar. 2010 7TeV run
July 2010 Removal of the LHCf detector from IP1
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