The LHCf experimentThe LHCf experiment

Hiroaki MENJO INFN Firenze

on behalf for the LHCf collaboration

at 29 March 2010, MC4LHC

Outline

What is the LHCf experiment ? - LHCf is one of forward experiments at LHC, with calorimeters covering Why does LHCf look at the very forward region ?

- To measure the most energetic secondaries which make an important role in air shower developments of cosmic rays.What can LHCf measure ? - Energy spectra and PT distribution of neutral particles,

gamma-rays, neutrons and .

LHCf = “LHC forward”

ATLASLHCb

CMS/TOTEM

ALICE

- LHCf collaboration - 6 countries12 institutes31 members

LHCf

Location

ATLAS

140m

LHCf Detector(Arm#1)

LHCf Detector (Arm#2)

96mm140m

96mm IP

TAN Detector

Inside of TAN-Neutral particle absorber-

The detector has been installed in 96mm gap of the beam pipes.

Neutral particles

charged particles

Detectors at zero degree of collisions

The Main Calorimeters

40mm

20mm Schematic view of the calorimeters in Arm#1

Sampling Calorimeter• W 44 r.l , 1.7λI • Scintilator x 16 LayersPosition Detector• Scifi x 4 (Arm#1)• Silicon strip detector x 4 (Arm#2)

Expected Performance: Energy resolution (> 100GeV) < 5% for photons 30% for neutrons Position resolution < 200μm (Arm#1) 40μm (Arm#2)

25mm

32mmSchematic view of the calorimeters in Arm#2

Two independent calorimeters allow to reconstruct π0

Arm#1Arm#1 Arm#2Arm#2

280mm280mm

92mm 90mm

620mm 620mm

Beam test at SPS Energy Resolution for electrons with 20mm cal.

Position Resolution (Scifi)

Position Resolution (Silicon)

Detector

p,e-,mu

σ=172μmfor 200GeVelectrons σ=40μm

for 200GeVelectrons

- Electrons 50GeV/c – 200GeV/c- Muons 150GeV/c- Protons 150GeV/c, 350GeV/c

10m

Fixed TargetAcrylic or Carbon

Arm#1 Detector

reconstruction at a beam test

mass was reconstructed from gamma-ray pair measured by the both two calorimeters

Calibration over SPS energy

Light Intensity(MIPs)

AD

C c

ount

s(0.

025p

C) 70,000 MIPs eq.

Response of all PMTs for large amount of light over SPS energyupto 70,000 MIPs eq. (7TeV elemag shower)has been calibrated by a fast N2 laser.

Sub detectors -Front Counter-

Thin scintillators with 8x8cm2 acceptance, which have been installed in front of each main detector.

• To monitor beam condition. • For background rejection of beam-residual gas collisions by coincidence analysis

Schematic view of Front counter

http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHCF

Movable detectors

Shadow of beam pipesbetween IP and TAN

neutral beam axis

Transverse projection of Arm#1 calorimeters

Transverse projection of Arm#1 calorimeters at zero-crossing angle.

neutral beam axis

η

∞

8.7

Shadow of beam pipesbetween IP and TAN

Transverse projection of Arm#1 calorimeters

at crossing angle of 140urad. η

∞

8.4

Shadow of beam pipesbetween IP and TAN

neutral beam axis

Detectors in LHC

Detectors in slots of TANlocated 140m far from IP1

IP1,ATLAS

= Why the very forward region =The motivation comes from observations

of Ultra High Energy Cosmic-Rays (UHECRs).

AGN etc.

~1020eVDepth[g/cm2]

ProtonFe

Photons

E=1019eVXMAX

AGASAHiRes

AUGERTA

-Experiments-

<X

MA

X>

[g/c

m2] Proton

Iron

1019eV1018eV

<Xmax> : one of indicators for cosmic-ray composition

Phys. Rev. Lett., 2010, 104, 091101

EPOS

QGSJET2

= Why the very forward region =Uncertainty of hadron interaction models induces effective

systematic error, especially for composition study of UHECRs.

But now we have LHC to calibrate interaction models at 7+7TeV pp, equivalent to 1017eV in lab. !!

Key parameters Total cross section ↔ TOTEM, ATLAS(ALFA) Multiplicity ↔ Central detectors Inelasticity/Secondary spectra ↔ Forward calorimeters LHCf, ZDCs

Rapidity distributions at 7+7TeV pp

In forward region (),

Quite Low multiplicity, but

Covering > 50% of total energy flux.

= Multiplicity = = Energy Flux =

Calculated with DPMJET3, dashed line: neutral particles

η> 8.4

XF 0.1 1.0

η> 8.7

Spectra of Secondary gamma-rays

Ratio Detectable/All

Most of all energetic neutral particle (XF>0.1)are detectable by LHCf

What LHCf can measure

Energy spectra and Transverse momentum distribution of

Gamma-rays (E>100GeV,E/E<5%)Neutral Hadrons (E>a few 100 GeV, E/E~30%)

Neutral Pion (E>700GeV, E/E<3%)

at psudo-rapidity range >8.4

LHCf can measure only inclusive spectra !!LHCf trigger is completely independent on ATLAS trigger.

However it is possible to identify coincidence events with ATLAS event by offline, and to analyze with center region (ATLAS) in future.

= What can LHCf measure ? =

MC model discrimination at 14TeV

n

at 7TeV + 7TeV pp106 collisions

↔ 2min. exposure @ 1029cm-2s-1

n w/o resolution

　 Reconstruction of

MC model discrimination at 14TeVExpected Measurement spectrum by Arm1

= PT distribution =

107 collisions

↔ 20min. exposure @ 1029cm-2s-1

MC model discrimination at 7TeV

at 3.5TeV + 3.5TeV pp

n

Energy spectra

with 30% energy resolution

1.5 x 106 collisions

↔ 3min. exposure @ 1029cm-2s-1

with 5% energy resolution

We will see 7TeV collisions tomorrow !!

MC model discrimination at 900GeV

at 450GeV + 450GeV pp

n

w/o resolution

DPMJET3QGSJET2QGSJET1SYBILL

Expected energy spectra with the 20x20mm calorimeter

at 107 collisions

We took data in 2009 Backgrounds

w/o resolution

Preliminary resaults at 900GeVIn last year, LHCf took 6,000 shower events

at 900GeV collisions. ↔ > 106collisions at all IPs.

Shadowof beam pipes

Red: colliding bunch = collision + BGBlue: single bunch = BG only

Presented at 18-Dec-2009

Preliminary resaults at 900GeV

MC with DPMJET3Data in 2009

preliminarycan say nothing about hadron results

for the moment !Checking detector response for hadrons

carefully by beam test data.

Analysis is ongoing, and we will get more statistic soon !!

Presented at LHCC 17-Feb-2009

Not ca

libra

ted

yet

Operation Plan

2009 Took data at 900GeV collision. ~6,000 shower events

2010 Take data at 900GeV again.

Operation at 3.5+3.5TeV till 2 pb-1.Then remove detectors and upgrade them.

2013 Install detectors again. Operation at 7+7TeV

+ we want to measure at intermediate energy ~1.5+1.5TeV, if LHC has. + we want to measure at light Ions+Ions collisions.

We will take data in LHC commissioning phases with low luminosity at every collision energy.

Summary

The LHCf experiment is one of forward experiments at LHC, with calorimeters covering LHCf looks at very forward region to measure the most energetic secondaries which play an important role in air shower developments of cosmic rays.

LHCf can measure energy spectra and PT distribution of neutral particles,

gamma-rays, neutrons and .

Backup

Arm1 event

Arm2 event

Arm2 neutron event

Transition curve in the calorimetric towers is used to discriminate between and n

: L90%<20 X0

n: L90%>20 X0