1. LHCf Measurements of Very Forward Particles at LHC
Takashi SAKO
(Solar-Terrestrial Environment Laboratory,
Nagoya University, Japan)
For the LHCf Collaboration
XVI International Symposium on Very High Energy Interactions, 28 Jun-3 Jul 2010, Fermilab

2. Air shower experiments2
Astrophysical parameters
- source type
- source distribution
- source spectrum
- source composition
- propagation
Image from “The Daily Galaxy”
Air shower development
- interaction
- atmosphere
Observations
- lateral distribution
- longitudinal distribution
- particle type
- arrival direction

3. Uncertainty in Hadron Interaction
Auger, PRL (2010)
Experimental data at highest energy hadron collider is indispensible => LHC

4. The Ｌarge Ｈadron Ｃollider
Collider of 7TeV proton + 7TeV proton
labo. System
Heavy ion collisions
ATLAS / LHCf
LHCb
CMS / TOTEM
ALICE

5. What to be measured at colliders multiplicity at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2))
Multiplicity
All particles
neutral
Most of the collision products are emitted in the central region

6. What to be measured at colliders multiplicity and energy flux at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2))
Multiplicity
Energy Flux
All particles
neutral
Most of the energy flows into very forward

7. LHCf Experiment
To measure very forward (η>8.4; including 0 degree) neutral particles at LHC p-p (ion-ion) collisions
International collaboration of Japan-Europe-USA (36 members)
ATLAS / LHCf
LHCb
CMS / TOTEM
ALICE
LHCf
LHCf

8. The LHCf experiment
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
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
G.Sinatra, A.Tricomi INFN, Univ. di Catania, Italy
J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain
D.Macina, A-L.Perrot CERN, Switzerland

9. Detector Location ATLAS 96mm LHCf Detector(Arm#1)
Two independent detectors at either side of IP1 ( Arm#1, Arm#2 )
96mm
140m
96mm
LHC IP
TAN
Detector
TAN -Neutral Particle Absorber-
transition from one common beam pipe to two pipes
　　Slot : 100mm(w) x 607mm(H) x 1000mm(T)

10. ATLAS & LHCf

11. LHCf Detectors ＊Imaging sampling shower calorimeters
＊Two independent calorimeters in each detector (Tangsten 44r.l., 1.7λ, sample with plastic scintillators)
Arm#1 Detector
20mmx20mm+40mmx40mm
4 XY SciFi+MAPMT
Arm#2 Detector
25mmx25mm+32mmx32mm
4 XY Silicon strip detectors

12. Double Arm Detectors
Arm#1 Detector
Arm#2 Detector
290mm
90mm

13. 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

14. Expected Results at 14 TeV collisions (assuming 0.1nb-1 statistics)
Detector response not considered

15. Original Plan 34 32 Log(Luminosity [cm-2s-1]) 30 28 26
Beam energy (TeV)
Log(Luminosity [cm-2s-1])
LHCf ideal
LHCf removal
LHC
nominal

16. Real Life Original target >=2013 May-2010 Mar-2010 Dec-200934 32 30 28 26
Original target
LHCf Removal
End of June-2010
Log(Luminosity [cm-2s-1])
LHCf Ideal
>=2013
May-2010
Mar-2010
Dec-2009
Beam energy (TeV)

17. Results at LHC

18. 2009 Operation at 900GeV Collisions
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.

19. First Events at 900GeV collisions
Longitudinal development
Lateral (X)
Distribution
Lateral (Y)
Arm1
(SciFi)

20. First Events at 900GeV collisions
Arm2
(Silicon)
Longitudinal development
Lateral (X)
Distribution
Lateral (Y)
Distribution
Energy scale is calibrated at SPS below 200GeV

21. 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

22. Both detectors give same spectra
Comparison between calorimeter towers of Arm2
Gamma-ray like
Hadron like
Blue: including 0 degree
Red: off axis
No angular dependence
Comparison between two Arms
Blue: Arm2
Red: Arm1
Preliminary
Preliminary
Both detectors give same spectra

23. Spectra Comparison with MC (QGSJET2) prediction
Conservative systematic error is assigned
x15 statistics was obtained in the 2010 operation

24. 7 TeV (3.5TeV+3.5TeV) Operation
First collision on 31-March 2010
Already accumulated about 14 nb-1

25. Have you ever seen TeV showers? (except CRs)
Gamma pair from TeV pi0
TeV gamma

26. Pi-zero (10% of full data)
Arm1
Arm2

27. Energy spectra from first 1% data
Hit map
Very low BKG
Angular dependence is seen
Stronger 0 degree concentration in hadron candidates

28. What’s next Operation Analysis
LHC started crossing angle run last week
LHCf can enlarge the PT coverage
Due to radiation damage LHCf removes the detectors in this summer
Detector will be upgrated to rad-hard by 14TeV collisions (2013 earliest)
Analysis
15 times more statistics in 900GeV data
>100 time statistics in 7TeV data
Systematics study rather than statistics
Conversion to production spectra (cross section)
Comparison with MC

29. Not only highest energy, but energy dependence…
7 TeV
10 TeV
14 TeV
QGSJET2
7 TeV
10 TeV 14
SIBYLL
Note: LHCf detector taken into account (biased)
Secondary gamma-ray spectra in p-p collisions at different collision energies (normalized to the maximum energy)
SIBYLL predicts perfect scaling while QGSJET2 predicts softening at higher energy
Qualitatively consistent with Xmax prediction

30. Summary
LHCf is a dedicated experiment to measure very forward neutral particles at LHC
LHCf successfully started (and almost finished) data taking at 900GeV and 7TeV collisions
We have sufficient statistics and started careful study in systematics to test hadron interaction models
We will remove the detectors soon and come back at 14TeV collisions with upgraded detectors

31. Backup

32. Light Nuclei collisions (Note: Not planned in LHC!!)
Energy flux in Nitrogen collisions
Still strong concentration in the forward region

33. Expected spectra in N-N collisions
Assuming to measure at the LHCf installation location
Gamma spectra at <1cm from 0 degree
clear difference in QGSJET2 and DPMJET3
Neutron spectra at <1cm from 0 degree
dominated by fragmentation neutron
Neutron spectra at 1-2cm (off center)
clear difference in high energy part

34. 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