1. The status and preliminary results of the LHC forward experiment: LHCf
Hiroaki MENJO
INFN Firenze, Italy
for the LHCf collaboration
DIS2010, Florence, 21 April 2010

2. Outline LHCf = “LHC forward” Introduction.
Detector : calorimeters covering h > 8.4 in IP1.
Measurement : energy spectra and PT distributions of energetic neutral particles.
Preliminary results in 900GeV collisions
Very preliminary results at 7TeV collisions
Operation plan in this year and in future.

3. The LHCf collaboration
Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, K.Noda, T.Sako, 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 3

4. -Neutral particle absorber-
Location
LHCf Detector(Arm#1)
ATLAS
140m
Inside of TAN
-Neutral particle absorber-
LHCf Detector (Arm#2)
96mm
Detectors at zero degree of collisions
In the long straight sections, there are big absorbers call TAN to protect the super conducting magnets.
at IP1 TAN are located 140m far from IP. Inside TAN beam pipe makes transition from one big pipe
to two small pipes. The gaps between the two pipes allow to see collisions at zero degrees.
TAN has an experimental slot to insert forward detectors inside the gap.
LHCf detectors had been installed in the first slot.
In secondary particles produced at collisions, charged particles are bended by dipole magnet installed between TAN and
interaction point. but we can see neutral particles at zero degree.
140m
96mm IP
TAN
Detector
Neutral particles
charged particles
The detector has been installed in 96mm gap of the beam pipes.

5. The LHCf detectors Sampling and Positioning Calorimeters Front Counter
25mm
32mm
W (44 r.l , 1.7λI ) and Scintillator x 16 Layers
4 positioning layers XY-SciFi(Arm1) and XY-Silicon strip(Arm#2)
Each detector has two calorimeter towers, which allow to reconstruct p0
Expected Performance
Energy resolution (> 100GeV)
< 5% for photons
30% for neutrons
Position resolution < 200μm (Arm#1)
40μm (Arm#2)
Schematic view of
the calorimeters in Arm#2
40mm
20mm
Schematic view of the calorimeters in Arm#1
The Arm#1 and Arm#2 , each detector has two sampling and imaging calorimeters.
The each calorimeter are made of 44 r.l. tungsten layer and 16 scintillator layers and 4 position sensitive layers.
The position sensitive layers of Arm#1 are made of XY pair of scintillating fiber bundles.
The position sensitive layers of Arm#2 are made of XY silicon strip detectors.
Two independent calorimeters allow to reconstruct neutral pion from pair photons.
The energy resolution is less than 5% for photons with more than 100GeV and about 30 % for neutrons.
The position resolution of Scintillating fibers in Arm1 is less than 200 um.
And position resolution of silicon detectors in Arm2 is about 40um.
Front Counter
thin scintillators with 80x80mm2
To monitor beam condition.
For background rejection of beam-residual gas collisions by coincidence analysis

6. Arm#1 Arm#2 620mm 620mm 280mm 92mm 90mm 280mm
These are photos of the real LHCf detectors.
The LHCf detectors are really compact to insert to inside of narrow experimental slot of TAN.
There are calorimeter towers inside of light green materials on bottom of the detectors.
280mm
92mm
90mm
280mm

7. Transverse projection of Arm#1
IP1,ATLAS
Arm2 η ∞
8.7
Shadow of beam pipes
between IP and TAN
8.4
This is photos of our detectors installed in the LHC ring.
The red one is the surface of TAN located 140m far from IP1. we can see our electronics boxes on TAN but detector were completely in experimental slots of TAN.
Behind of our detectors, Luminosity monitor BRAN and ATLAS ZDC has been installed. ∞
@ 140mrad crossing angle
neutral beam axis
Transverse projection of Arm#1
@ zero crossing angle

8. LHCf can measure
Energy spectra and Transverse momentum distribution of
Gamma-rays (E>100GeV,dE/E<5%)
Neutral Hadrons (E>a few 100 GeV, dE/E~30%)
Neutral Pions (E>700GeV, dE/E<3%)
at psudo-rapidity range >8.4
The Aim is to calibrate hadron interaction models
for ultra high energy cosmic ray physics.
Next, I present what we can measure.
We can measure energy spectra and transverse momentum distribution of gamma-ray with more than 100GeV
and neutral hadrons it’s mainly neutrons with more than a few hundreds GeV, and neutral pions with more than 700GeV
at rapidity range from 8.4 to infinity.
because we don’t have own central detectors and LHCf trigger is completely independent on ATLAS trigger,
so LHCf can measure only inclusive spectra . However we are recording ATLAS event ID number event by event,
so it is possible to identify coincidence events with ATLAS event and to analyze with ATALS in future.
Energy
High energy flux !!
Low multiplicity !!
simulated by DPMJET3

9. = Operations in 2009 = With stable beams at 900GeV, 06.Dec. – 15.Dec
2.6 hours for commissioning
27.7 hours for physics
~2,800 shower events in Arm1
~3,700 shower events in Arm2
~5x105 collisions at IP1
Expected spectra with each hadron interaction model
Gamma-ray Arm2
Hadron Arm2
with 107 col.

10. Results at 900GeV
shadow
of beam pipes
Hit map of Gamma-rays
Arm1
Background due to beam-residual gas collision is about 10%
Red: colliding bunch = collision + BG
Blue: single bunch
= BG only
I shows preliminary resutls in last year operation.
in last year, in total LHC had about 10 to 6th collisions at all IPs.
We took about 6000 shower events by Arm1 and Arm2 calorimeters.
The left figure show the hit map of gamma-ray events. black open circles show events at colliding bunches and
red marks shows events at non-colliding bunches. beam and residual gas collisions made these non-colliding bunch events.
Black markers have clear cut because of the beam pipe shadow.
Left figure show distribution of energy deposit in Arm1 detectors.
Red dots shows events at colliding beams and Blue shows events at non-colliding beam events.
By subtract with non-colliding beam events, we can see clear collision events.
Arm2

11. Particle Identification
A transition curve for Gamma-ray
A transition curve for Hadron
Thick for E.M. interaction (44X0)
Thin for hadronic interaction(1.7l)
20mm cal. of Arm1
Definition of L90%
MC (QGSJET2)
Data
Preliminary
Criteria for gamma-rays
16 r.l x SdE
Gamma-ray like

12. Comparison of spectra Spatially flat profile in h>8.7 at 900GeV
Comparison between calorimeter towers of Arm2
Comparison of spectra
Gamma-ray like
Hadron like
Spatially flat profile in h>8.7
at 900GeV
Comparison between two Arms
Both detectors give consistent spectra
Preliminary
Preliminary

13. Comparison with MC @ Arm1
MC(QGSJET2)
Data
Sys.+Sta.
Hadron response
under study
Spectra of MC are normalized by the entries of gamma-ray spectra
Data is in good agreement with MC
Checking detector response for hadrons carefully by beam test data with 150GeV, 350GeV protons.
Studying systematic errors. for the moment. Sys. of Energy scale (+11% /-5%)

14. Comparison with MC @ Arm2
Hadron response
under study
More statistics by data taking at 900GeV soon

15. = Operations in 2010 = 1 TeV gamma-ray shower @ Arm2
Data taking at 7TeV collisions is ongoing !!!
Already 7x106 shower events in Arm1 and Arm2 have been collected (30th Mar. - 19th Apr. 2010)
Transition curve in small tower
1 TeV gamma-ray Arm2
X-view of silicon strip
Y-view of silicon strip

16. Very preliminary results
High statistics !!
Only 1.5% of total data are used
Very clean data!!
BKG due to beam-gas
collisions is ~ 1%

17. Operation Plan
We will take data in LHC commissioning phases with low luminosity at every collision energy.
2009
Took data at 900GeV collision. ~6,000 shower events
2010
Take data at 900GeV again.
Operation at 7TeV until 2 pb-1. Then remove detectors and upgrade them.
2013
Install detectors again. Operation at 14TeV
Finally I present our operation plan. We will take data in beginning of LHC commissioning phases with very low luminosity
at every collision energy.
In this year, we will take data at 900GeV and 7TeV collisions until the integral luminosity of 2pb-1, then we will remove the
detectors and upgrade them for next operation. In 2013, LHC will finish to upgrade for 14TeV, we will install the detectors again to take data at 14 TeV collisions.
And also we want to take data at intermediate collision energy and light lions collisions if LHC has.
+ we want to measure at intermediate energy ~3TeV, if LHC has.
+ we want to measure at light Ions collisions in some future.

18. Summary The LHCf experiment is At 900GeV pp collisions,
a forward experiment of LHC with calorimeters at zero degree.
measuring energy spectra and transverse momentum distributions of very energetic neutral secondaries at the very forward region of IP1 (h>8.4).
At 900GeV pp collisions,
We successfully took 6,000 shower events in the last year operations.
Measured gamma-ray energy spectra are in good agreements with MC within statistics and systematic errors.
We are checking hadron response of the detectors and systematic errors.
More statistic data will be taken in operations soon.
At 7TeV pp collisions,
Data taking is ongoing successfully.
We will operate until 2pb-1 Integral luminosity (for a few months)

19. Buck up

20. Sub detectors -Front Counter-
Thin scintillators with 8x8cm2 acceptance, which have been installed in front of each main detector.
Schematic view of
Front counter
We have a sub-detector with thin scintillator layers, we call Front Counter.
Front Counter has much larger acceptance than calorimeters.
It’s useful to monitor collisions and for background rejection of beam and residual gas collisions by coincidence analysis of both size.
To monitor beam condition.
For background rejection of beam-residual gas collisions by coincidence analysis

21. Beam test at SPS p,e-,mu σ=172μm σ=40μm Detector Energy Resolution
for electrons with 20mm cal.
- Electrons 50GeV/c – 200GeV/c
Muons 150GeV/c
Protons 150GeV/c, 350GeV/c
Position Resolution (Silicon)
Position Resolution (Scifi)
The detector performance was checked by beam tests at SPS.
We had exposed the detectors in electron, muon and protons beams with a few hundreds GeV.
This is energy resolution of one of the calorimeters as a function of gamma-ray energy.
It is in a very good agreement with simulation results and good resolution of 5% for more than 100GeV.
And bottom figures show position resolution of scintillating fibers of Arm1 and silicon detectors of Arm2 for 200GeV electrons.
σ=172μm
for 200GeV
electrons
σ=40μm
for 200GeV
electrons

22. p0 reconstruction at the beam test
Fixed Target
Acrylic or Carbon
Arm#1
Detector
p0 mass was reconstructed from
gamma-ray pair measured by the both two calorimeters
Calibration over SPS energy
70,000 MIPs eq.
Light Intensity(MIPs)
ADC counts(0.025pC)
In the beam test, we had a special run to demonstrate pi0 reconstruction capability of our detectors.
we put target material on the beam line of protons to produce neutral pions at 10m far from the detector.
This is reconstructed invariant mass from gamma-ray pairs measured by the Arm1 detector.
we can see clear peak of pi0 mass.
Then calibration over a few hundreds GeV was done by nitrogen laser.
We checked PMT response for light amount equivalent shower maximum of 7TeV gamma-rays.
Response of all PMTs
for large amount of light over SPS energy
upto 70,000 MIPs eq. (7TeV elemag shower) has been calibrated by a fast N2 laser.

23. Pi0 mass at 7TeV Good estimator of systematic errors Preliminary
in Arm2
Preliminary
Mean:
134.5MeV
Sigma :
4.2 MeV
Data taken at 30. March
is used (~1.5% of total)
Good estimator of
systematic errors