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