The LHCf experiment at LHC

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The LHCf experiment at LHC
ISVHECRI08 - XV International Symposium on Very
High Energy Cosmic Ray Interactions Paris 1 6
September, 2008

• Alessia Tricomi
• University and INFN Catania
• on behalf of the LHCf Collaboration

• Experiment goals
• The LHCf detector
• Physics performance
• Running plan

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The LHCf Collaboration
CERN D.Macina, A.L. Perrot
USA LBNL Berkeley W. Turner
FRANCE Ecole Politechnique Paris M. Haguenauer
SPAIN IFIC Valencia A.Fauss, J.Velasco
JAPAN STE Laboratory Nagoya University K.Fukui,Y
.Itow, T.Mase, K.Masuda,Y.Matsubara,
H.Menjo,T.Sako, K.Taki, H. Watanabe Waseda
University K. Kasahara, M. Mizuishi, Y.Shimizu,
S.Torii Konan University Y.Muraki Kanagawa
University Yokohama T.Tamura Shibaura Institute
of Technology K. Yoshida
ITALY Firenze University and INFN O.Adriani,,
L.Bonechi, M.Bongi, G.Castellini, R.DAlessandro,
P.Papini, S. Ricciarini, A. Viciani Catania
University and INFN A.Tricomi
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LHCf modelling Cosmic Rays at LHC
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The Cosmic Ray Spectra
super GZK events?!?
Different results between different experiments
Based on data presented at the 30th ICRC Merida
(Mexico) Figure prepared by Y. Tokanatsu
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The Cosmic Ray Spectra
Difference in the energy scale between different
experiments???
AGASA x 0.9 HiRes x1.2 Yakutsk x 0.75 Auger x1.2
(not enough)
Berezinsky 2007
AGASA Systematics Total
18 Hadron interaction
(QGSJET, SIBYLL) 10
(Takeda et al., 2003)
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Cosmic Ray Composition
Not only GZK Different interaction models lead
to different conclusions about the composition of
the primary cosmic rays.
Xmax(g/cm2)
Energy (eV)
Knapp et al., 2003
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Cosmic Ray Composition
Xmax favors heavy primary
Anisotropy favors light primary (if accept AGN
correlation)
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Cosmic Ray Composition
Kascade Results
QGSJET01
SIBYLL 2.1
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Need for calibration
Composition inferred from Xmax Spectrum Energy
is measured by counting the secondaries Simulat
ion plays a crucial role
LHCf is a tool to calibrate the simulation
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Development of atmospheric showers
Simulation of an atmospheric shower due to a 1019
eV proton.
The dominant contribution to the energy flux is
in the very forward region (? ? 0)
XFE/E0
No cut g XFlt0.05 p, K XFlt0.1
In this forward region the highest energy
available measurements of p0 cross section were
done by UA7 (E1014 eV, y 57)
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Forward Physics at LHC
LHCf firstly proposed to use LHC, the highest
energy accelerator 14 TeV in the center of mass
Elab1017 eV (Elab E2cm/2 mP) to calibrate MC
simulation code
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But
General purpose detectors (ATLAS, CMS,) cover
only the central region
Special detectors to access forward particles are
necessary
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How to access Very Forward Physics at LHC?
Surrounding the beam pipe with detectors Simple
way, but still miss very very forward particles
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How to access Very Forward Physics at LHC?
Install detectors inside the beam
pipe Challenging but ideal for charged particle
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How to access Very Forward Physics at LHC?
Charged particles
LHCf
Neutral particles
Beam pipe
Y shape chamber enables us neutral
measurements Zero Degree Calorimeters
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Pseudo rapidity in LHC
Energy flow
Transverse energy flow
The CMS and TOTEM diffractive and forward physics
working group
pseudorapidity ? - ln (tan ?/2)
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The LHC ring
27 km ring
ATLAS LHCf
IP1
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LHCf location and detector layout
Detector II Tungsten Scintillator Silicon mstrips
Detector I Tungsten Scintillator Scintillating
fibers
INTERACTION POINT IP1 (ATLAS)
140 m
140 m
Beam line

• Two independent detectors on both side of IP1
• Redundancy
• Background rejection (especially beam-gas)

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LHCf location
Detectors installed in the TAN region, 140 m away
from the Interaction Point, in front of
luminosity monitors

• Here the beam pipe splits in 2 separate tubes.
• Charged particle are swept away by magnets!!!
• We will cover up to y??

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Detector 1
Impact point (h)
2 towers 24 cm long stacked vertically with 5 mm
gap Lower 2 cm x 2 cm area Upper 4 cm x 4 cm
area
4 pairs of scintillating fiber layers for
tracking purpose (6, 10, 32, 38 r.l.)
Absorber 22 tungsten layers 7mm
14 mm thick (W X0 3.5mm, RM 9mm)
16 scintillator layers (3 mm thick) Trigger
and energy profile measurements
Energy
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Detector 2
We used LHC style electronics and readout
Impact point (h)
2 towers 24 cm long stacked on their edges and
offset from one another Lower 2.5 cm x 2.5
cm Upper 3.2 cm x 3.2 cm
4 pairs of silicon microstrip layers (6, 10, 30,
42 r.l.) for tracking purpose (X and Y directions)
16 scintillator layers (3 mm thick) Trigger
and energy profile measurements
Absorber 22 tungsten layers 7mm
14 mm thick (2-4 r.l.) (W X0 3.5mm, RM
9mm)
Energy
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Double ARM Detectors
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Detectors in place

• Installation performed in two phases
• Pre-Installation (Jan/Apr 2007)
• Baking out of the beam pipe (200 C)
• Final Installation (Jan 2008)

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LHCf Physics performance

• Single photon spectrum
• p0 fully reconstructed (1 g in each tower)
• p0 reconstruction is an important tool for
  energy calibration (p0 mass constraint)
• Basic detector requirements
• minimum 2 towers (p0 reconstruction)
• Smallest tower on the beam (multiple hits)
• Dimension of the tower ? Moliere radius
• Maximum acceptance (given the LHC constraints)

Results for the moment based on
Unfortunately no LHC data still available
Simulation
Beam Test
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LHCf acceptance on PTg-Eg plane
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Beam crossing angle
Detectable events
A vertical beam crossing angle gt 0 will increase
the acceptance of LHCf
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LHCf single g geometrical acceptance
Some runs with LHCf vertically shifted few cm
will allow to cover the whole kinematical range
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Transverse projection in TAN slot
ARM1 Maximization of the acceptance for vertical
beam displacement (crossing anglegt0)
ARM2 Maximization of the acceptance in R
(distance from beam center)
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LHCf Monte Carlo discrimination
106 generated LHC interactions ? 1 Minute
exposure_at_1029 cm-2s-1 luminosity
Discrimination between various models is
feasible
Quantitative discrimination with the help of a
properly defined c2 discriminating variable based
on the spectrum shape (see TDR for details)
5 Energy resolution
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LHCf model dependence of neutron energy
distribution
Original n energy
30 energy resolution
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New Models
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Proton
PICCOEPOS
Drescher, Physical Review D77,
056003 (2008)
p0
Neutron
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p0 spectra
p0 produced at collision can be extracted by
using gamma pair events Powerful tool to
calibrate the energy scale and also to eliminate
beam-gas BG
QGSJETII ? DPMJET3?2 106 (C.L. lt10-6) ? SIBYLL
?2 83 (C.L. lt10-6) DPMJET3 ? SIBYLL ?2 28
(C.L. 0.024) 107events DOF 17-215
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LHCf performances p0 mass resolution
Arm 1 DE/E5 200 mm spatial resolution
Dm/m 5
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SPS Beam Test

• Test was successful
• Analysis is under way for
• Energy calibration of the calorimeters
• Spatial resolution of the tracking systems

• CERN SPS T2 H4
• 2006 Aug. 28 Sep. 4
• Incident Particles
• Proton 150,350 GeV/c
• Electron 50,100, 50,200 GeV/c
• Muon 150 GeV/c

Setup
Trigger Scintillator
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Energy Resolution
Monte Carlo
N Particles
MC predicts that the leakage is energy
independent!
Distance from Edge
SPS bean test
Energy distribution is corrected for leakage
correction
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p0 reconstruction
g
350 GeV Proton beam
Not in scale!
g
Carbon target (6 cm) in the slot used for beam
monitor
9.15 m
Arm1

• gt107 proton on target (special setting from the
  SPS people)
• Dedicated trigger on both towers of the
  calorimeter has been used

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p0 mass reconstruction
? 250 p0 events triggered (in a quite big
background) and on disk
Preliminary!!!!
(MeV)

• Main problems
• low photon energy ( 20 GeV)
• Direct protons in the towers
• Multi hits in the same tower

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ARM1 Position resolution
200 GeV electrons
Number of event
sxmm
sx172 mm
x-posmm
EGeV
symm
sy159 mm
Number of event
y-posmm
EGeV
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ARM2 Position Resolution
200 GeV electrons
Number of event
sx40 mm
x-posmm
Number of event
sy64 mm
y-posmm
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ARM2-Silicon Energy Resolution
200 GeV electrons SPS beam test data
No correction/calibration applied
DE/E 12
ADC
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LHC schedule
Beam commissiong parameters are good for LHCf!
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LHCf possible running scenario

• Phase-I
• 900 GeV collision before ramping in 2008 (hope
  in a week from now!)
• 10 TeV run in 2008 during the LHC commissioning
  (low luminosity)
• 14 TeV run in 2009 during commissioning
• Remove LHCf when luminosity reaches 1030 cm-2s-1
  for radiation damage reasons
• Phase-II
• Re-install the detector at the next opportunity
  of low luminosity run
• Dedicated runs (crossing angle, etc.)
• Phase-III
• Future extension for p-A, A-A run with upgraded
  detectors are under study

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LHCf conclusions and plans

• Compilation of the EAS data is affected by the
  uncertainty of hadron interaction.
• LHCf experiment will provide crucial data of
  hadron interaction for CR study.
• LHCf can clearly discriminate the existing and
  new models by measurements of p0,? and n thanks
  to its excellent performances
• Energy Resolution 5
• Spatial resolution 40-200 mm
• Beam crossing angle ?0 and/or vertical shifts of
  LHCf by few cm will allow more complete physics
  measurements
• Both Detectors ready to fulfil the run program
• So now

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LHCf conclusions and plans
We need only to wait for LHC beams, which indeed
are just arriving! Hoping to answer all our
questions and to help EAS experiments to
interpret their data
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Back-up slides
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The TAN and LHCf
manipulator
marble shielding
boxes for DAQ electronic
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Lateral view of ARM 2
Front scintillator
Front scintillator Fixed position wrt to TAN
Silicon Tungsten Scintillator /- 5 cm
vertical excursion
Si Tracker Hybrid
PMTR7400
Beam axis
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g rate
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p0 rate
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g ray energy spectrum for different positions
QGSJETII used model QGSJET c2/DOF107/125 DPMJET
3 c2/DOF224/125 SYBILL c2/DOF816/125
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Estimate of the background

• beam-beam pipe
• ? E ?(signal) gt 200 GeV, OK
• background lt 1
• beam-gas
• ? It depends on the beam condition
• background lt 1 (under 10-10 Torr)
• beam halo-beam pipe
• ? It has been newly estimated from the beam
  loss rate
• Background lt 10 (conservative
  value)

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Effect of LHCf on BRAN measurement
LUMI monitor (BRAN) inside TAN is beyond LHCf
(replacing 4th copper bar)
IP1
Cu Bar / ZDC
Cu Bar / ZDC
LHCf
LHCf
Lumi
Lumi

• The effect of LHCf on BRAN measurements has been
  studied in the last months by simulation
• Reduction of shower particles at BRAN
• Position dependence on beam displacement
• (question from machine peoples if we shift by 1
  mm the real beam, does the center of the measured
  neutral energy shifts by 1 mm?)

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BRAN response vs beam position
Relative change of the reduction factors for BRAN
with respect to the nominal value (center of the
beam nominal one)
Arm 1
Arm 2
H.Menjo
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LHCf performances p0 geometrical acceptance
Arm 1
Arm 2
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LHCf performances energy spectrum of p0
Typical energy resolution of g is 3 at 1TeV
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Optimal LHCf run conditions

• Beam parameters used for commissioning are good
  for LHCf!!!

( No radiation problem for 10kGy by a year
operation with this luminosity )
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The LPM effect
Transition curve of a1 TeV photon w/ and w/o LPM
to be measured by LHCf
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Radiation Damage Studies
Scintillating fibers and scintillators

• Expected dose 100 Gy/day at 1030 cm-2s-1
• Few months _at_ 1030 cm-2s-1 10 kGy
• 50 light output
• Continous monitor and calibration with Laser
  system!!!

30 kGy
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Scintillating fibers readout (Arm1)
Hamamatsu 64 ch (8x8) 8 dynode
MAPMT

• VA32HDR14 chip from IDEAS
• 1 ms shaping time
• Huge dynamic range (30 pC)
• 32 channels

MAPMTFEC
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Silicon mstrip redout
Pace3 chips (many thanks to CMS preshower!!!!)

• 32 channels
• 25 ns peaking time
• High dynamic range (gt 400 MIP)
• 192x32 analog pipeline

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LHCf can measure (and provide to LHC) the center
of neutral flux from the collisions
particles
Position sensitive layers
If the center of the neutral flux hits LHCf ?
ltlt 1 mm resolution
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The problem of the Energy Scale
AGASA reports 18 systematic uncertainty in
energy determination 10 of systematic is due to
interaction model
20 correction on the absolute energy scale!!!
Agasa HiRes Data
Different interaction models give different
answers for the primary cosmic ray energy
estimate Accelerator calibration is mandatory