LHCf: stato e programmi
Oscar Adriani
CSN1,Torino, 27 settembre 2012
Introduction and contents
 Analyses
 p0 paper accepted by PRD
 900 GeV g paper published on PLB
 Short spot on other analyses
 Arm1 preparation for 14 TeV
 Beam test at SPS (August-September 2012)
 Arm2 preparation for p/Pb 2013 run
LHCf: location and detector layout
Detector I
Tungsten
Scintillator
Scintillating fibers
INTERACTION POINT
IP1 (ATLAS)
Front Counter
140 m
γ
Front Counter
140 m
8 cm
n
π0
Detector II
Tungsten
Scintillator
Silicon mstrips
6 cm
γ
44X0,
1.6 lint
Arm#1 Detector
20mmx20mm+40mmx40mm
4 X-Y SciFi tracking layers
Arm#2 Detector
25mmx25mm+32mmx32mm
4 X-Y Silicon strip tracking layers
π0 analysis: PT spectra for
different rapidity bins
“Measurement of forward neutral pion transverse
momentum spectra for √s = 7TeV proton-proton
collisions at LHC“
‘Accepted’ by PRD
π0 analysis at √s=7TeV
Type-I
Submitted to PRD (arXiv:1205.4578).
Type-II
•Large angle
•Simple
•Clean
•High-stat.
Type-I
LHCf-Arm1
Type-II
LHCf-Arm1
•Small angle
•large BG
•Low-stat.
, but can cover
•High-E
•Large-PT
LHCf-Arm1
Data 2010
Preliminary
Type-II at large
tower
BG
Type-II at small
tower
Signal
Type I π0 analysis procedure
g1(E1)
R
Mass, energy and transverse momentum
are reconstructed from the energies and
impact positions of photon pairs measured
by each calorimeter
R
=
140 m
140m
g2(E2)

I.P.1
Analysis Procedure
•
•
•
•
•
Standard photon reconstruction
Event selection
- one photon in each calorimeter
- reconstructed invariant mass
Background subtraction
by using outer region of mass peak
Unfolding for detector response.
Acceptance correction.
Dedicated part for π0 analysis
Submitted to PRD (arXiv:1205.4578).
Acceptance and unfolding
• Remaining background spectrum is estimated using the
sideband information, then the BG spectrum is
subtracted from the spectrum obtained in the signal
window.
Validity check of unfolding method
True EPOS
Unfolded(by π0+EPOS)
Unfolded(by π0+PYTHIA)
LHCf-Arm1
√s=7TeV
9.0<y<11.0
Measured EPOS
Acceptance for π0 at LHCf-Arm1
• Raw distributions are corrected for
detector responses by an unfolding
process that is based on the iterative
Bayesian method.
(G. D’Agostini NIM A 362 (1995) 487)
• Detector response corrected
spectrum is then corrected for
acceptance
π0 results: Data vs MC
π
0 results: Data/MC
Submitted to PRD (arXiv:1205.4578).
Data/MC
commented

dpmjet 3.04 & pythia 8.145 show
overall agreement with LHCf data for
9.2<y<9.6 and pT <0.25 GeV/c, while
the expected p0 production rates by
both models exceed the LHCf data as
pT becomes large

sibyll 2.1 predicts harder pion
spectra than data, but the expected
p0 yield is generally small

qgsjet II-03 predicts p0 spectra softer
than LHCf data

epos 1.99 shows the best overall
agreement with the LHCf data.


behaves softer in the low pT region,
pT < 0.4GeV/c in 9.0<y<9.4 and pT
<0.3GeV/c in 9.4<y<9.6
behaves harder in the large pT
region.
<pT> distribution
Three different approaches used to derive
the average transverse momentum, ⟨pT⟩
1. by fitting an empirical function to the
pT spectra in each rapidity range
(exponential distribution based on a
thermodynamical approach)
2. By fitting a gaussian distribution
3. by simply numerically integrating the
pT spectra
Results of the three methods are in
agreement and are compared with UA7
data and hadronic model predictions.
Two UA7 and LHCf experimental data
show the same trend
→ no evident dependence of <pT>
on ECMS.
YBeam=6.5 for SPS
YBeam=8.92 for7 TeV LHC
900 GeV inclusive g spectra
“Measurement of zero degree single photon energy
spectra for √s = 900 GeV proton-proton collisions at LHC“
PLB 715 (2012) 298
CERN-PH-EP-2012-048
Comparison wrt MC Models at 900 GeV
g analysis:
Comparison btw 900 GeV and 7 TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
A jump back to g analysis:
Comparison btw 900GeV and 7TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
900GeV vs. 7TeV
with the same PT
region
900 GeV
Small+large
tower
A jump back to g analysis:
Comparison btw 900GeV and 7TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
XF spectra : 900GeV data vs. 7TeV data
Preliminary
900GeV vs. 7TeV
with the same PT
region
Data 2010 at √s=900GeV
(Normalized by the number
of entries in XF > 0.1)
Data 2010 at √s=7TeV (η>10.94)
900 GeV
Small+large
tower


Normalized by the number of entries in XF > 0.1
No systematic error is considered in both collision energies.
Good agreement of XF spectrum shape between 900 GeV and 7 TeV.
 weak dependence of <pT> on ECMS
Neutron and K0
(very preliminary…) analyses
Why neutron measurement is important
for CR physics
Auger hybrid analysis
• event-by-event MC selection to
fit FD data (top plot)
• comparison with SD data vs MC
(bottom plot)
• Clear muon excess in data even
for Fe primary MC
The number of muons increases
with the increase of the number of
baryons!
=> importance of direct baryon
measurement
Neutron Detection Efficiency and energy
linearity
Linear fit
Parabolic fit
%
Efficiency at the offline shower trigger
Flat efficiency >500GeV
Energy and Position Resolution
X
We are trying to improve the
energy resolution by looking at the
‘electromagneticity’ of the event
Y
Neutron incident at (X,Y) = (8.5mm, 11.5mm)
~1mm position resolution
Weak dependence on incident energy
K0 analysis
K0 Acceptance
Status of the LHCf
preparation for 14 TeV
LHCf preparation for the 14 TeV p-p run
 Calorimeter radiation hardening by replacing plastic scintillator with GSO
 Scintillator plates



3 mm  1mm thick scintillators
Acrylic  quartz light guides
 construction and light yield uniformity test carried out in Japan
SciFi



1 mm square fibers  1 mm GSO square bars
No clad-core structure (GSO bar)
 Attenuation and cross talk test carried out
Acrylic light guide fiber  quartz light guide fibers
 Construction and light yield test carried out
 Production and laboratory tests of the new scintillators in Japan is finished
 Beam test at Ion facility (HIMAC) has been done in June 2012
 Arm1 has been re-assembled in Florence starting from end of June
 Same procedure will be followed in 2013 for the Arm2 detector

Upgrade of the silicon positioning measurement system


Rearranging Silicon layers for independent precise energy measurement
Increase the dynamic range to reduce saturation effects
Beam test at the SPS
 Long beam test has been conducted from August 17th to
September 4th in the H2 SPS area
 Muons, 50-250 GeV electrons, 350 GeV protons
 More than 1 TB of data
 Main goals:
 Energy scale of upgraded Arm1 detector
 Check of energy scale of not upgraded Arm2 for the p/Pb run
 Test of the solution to improve the silicon saturation for 14 TeV
run
 Check of the temperature dependence of the absolute energy
scale both for Arm1 and Arm2
 Very successful beam test!
Test of new silicon pattern bonding
 Problem: saturation of the silicon electronics for Eg > 1.5 TeV
 Pace3 dynamic range is not enough to sustain such a huge
energy release
 Not a problem for 3.5+3.5 TeV runs
 Software corrections based on the different PACE3 samples allow
to increase saturation up to 2.5/3 TeV
 Become an issue for 7+7 TeV run
 We will change the silicon sensors position to improve the silicon
only energy resolution….
 We developed a new idea to hardware improve the saturation
level
Different silicon bonding scheme
80 mm implant pitch
160 mm readout pitch
Not used
Silicon sensor
Normal configuration
New configuration
Arm2 detector
New silicon
Pb (40mm)
The beam test setup
e-, 200 GeV/c
Readout
Floating
Readout
Readout
Ground
Readout
New Silicon Module results (Quick analysis)
 Clearly the pulse height in the region of new configuration were reduced by a
factor of 1.5 ~ 1.7 (we could naively expect 2)
 The modification works fine
to enlarge the silicon dynamic range
Silicon Lateral distribution
Normal
New
#Strip
Histogram of peak values
Arm2 Pi0 Mass v.s. Temperature at LHC
15-Mar.-2012 /
31-Mar-2012
Remember the 3.8% Mass Shift
that was longly discussed….
Temperature test and control at SPS
During the beam test,
we carefully controlled the
temperature of the
detector with a chiller
Water
We waited for some hours
until the temperature was
very stable (< 0.1 degree /
hour)
Temperature test (Arm2)
 Check the temperature dependency of the energy scale by
changing the chiller temperature to 18, 23, 28, 33 degrees.
Thermometer in Arm2
33
28
23
Chiller temperature
18
Energy scale temperature
dependence(Arm2)
The temperature coefficient
is consistent with the R7400U
catalog value (-0.20% /C)
We could confirm that there is
a dependence of energy scale
on the temperature.
Compatible with 3.8% mass
shift???? To be checked
Re-installation for the p/Pb run
 Arm2 will be re-installed in the TAN during the technical stop
foreseen at the end of the p/p run
 We have modified the LHCf support structure and cabling to
significantly reduce the installation required time
 The procedure for reinstallation has been carefully discussed in the
LTEX meetings and is ready
 Checked with RP  RP gave green light
 We are continuing discussions with ATLAS for trigger and data
exchange, to get the maximum physics outcome for the data,
following the LHCC recommendation
 Arm2 will be brought back to Florence after the p/Pb run
completion (special transport will be necessary because of the
slight radioactivity)
Miscellanea…. I
 Possibility to use LIGHT IONS in LHC from 2016/2017?
 Light Ion source setup is ongoing because of SPS interest
 RHIC run in 2015/2016 was under discussion…
 Please stand by a little bit to see how things are evolving!!!!
 We have a new Japanese expert post doc that will stay in Italy
for 2 years paid by Japan
Miscellanea II:
Working together with MC model developers
 Since the first paper we are in strict connection with model
developers (EPOS,QGSJET, SYBILL etc.)
 We have taken part to several meetings/workshops
 We are contributing to the tuning of the model to LHCf data
 We are also involved in the MCPLOTS/RIVET project
(http://mcplots.cern.ch)
 a simple browsable repository of MC (Monte Carlo) plots comparing
High Energy Physics event generators to a wide variety of available
experimental data, for tuning and reference purposes
Miscellanea III:
Working together with other LHC MC contacts
 Since last year we are involved in one of the WG of the
MC4LHC project
 A new WG is now starting to focus on astroparticle physics
connection with contact persons from each LHC experiments
 A. Tricomi, T. Sako
 Set up and organize a workshop
Miscellanea IV: LHCf computing
 Lo scorso anno abbiamo presentato un piccolo modello di calcolo per far fronte alle esigenze di
simulazione e ricostruzione di LHCf per il run p-Pb di cui siamo responsabili
 I referee ci hanno finanziato una parte di quello richiesto rimandando a quest’anno la seconda
parte a fronte di stime più precise per consentirci la produzione dei plot per la LOI
 Il data set per la LOI è stato prodotto interamente in Italia e le tre macchine acquistate sono
state fondamentali
 Abbiamo fatto i primi test di simulazione completa con p-Pb

500 KB per evento e 570 sec/evento con la simulazione completa

20 KB per evento e 22 sec/evento se applichiamo dei tagli cinematici abbastanza duri (eccessivi per
quello che vorremmo fare)

Una via di mezzo tra queste due, dell'ordine dei 100 KB e 100 sec/evento e' quella piu' realistica senza
perdere informazioni di fisica rilevanti.
 Noi abbiamo bisogno di produrre come minimo 107 eventi per ciascuno dei modelli studiati
(finora 5)
 Poichè le stime dello scorso anno, basate sulla sola generazione erano ben più ottimistiche di
quello che abbiamo ottenuto ora, chiediamo il completamento delle risorse. Per il disco
cercheremo di utilizzare risorse presenti in sezione ma abbiamo bisogno di CPU dedicate

15 Keuro per l’acquisto delle CPU
Miscellanea V: Missioni estere
 Ad Aprile 2012 la CSN1 ci aveva sbloccato 35 kE di Missioni
Estere che erano SJ al run p/Pb
 Dato che il run p/Pb è stato spostato al 2013, restituiamo alla
CSN1 27 kE di ME (21 kE da Firenze e 6 kE da Catania)
 Cerchiamo di effettuare più lavori possibile nel 2012
 Setup di control room e DAQ
 Test di interfaccia con la macchina
 Installazione meccanica nel tunnel
 Con la ragionevole speranza che ci vengano riassegnati per il
2013!!!!!!
Conclusions
 The analysis work is nicely going on
 Very important and tight contacts with the theorists and the model

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


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developers to maximize the outcome of the LHCf results
Arm1 upgrade has been completed
Arm2 is ready to be installed for the 2013 p/Pb run
Very successful test beam has been completed in summer 2012
Arm2 upgrade will be completed in 2013
Ready to take data at 14 TeV
And…. Possible Light Ions runs at RHIC/LHC are under investigation
Spares slides
Temperature dependency (Arm1)
The temperature dependency has been also checked for Arm1.
The coefficient of GSO may be bigger than PMT, about - 0.5% / degree.
Compared the histograms of dE in each layer at 18, 23, 28, 33 chiller temperatures.
18
23 28 33
T_Chiller
Layer 03
Layer 05
Layer 04
Layer 06
The coefficient is between 0.17% degree and 0.45% / degree.
Slightly bigger than Arm2, but not so serious.
Fast install/uninstall
Now 35 BNC
connections in
the tunnel
To be packed in 23 Harting
multipoles
connectors
Silicon strip FE
Calorimeters
LHCf main
electronics
amplifier
detector
Now 3 main structures installed separately
To be assembled in
a single structure
Radiation hardness of GSO
Dose rate=2 kGy/hour
(≈1032cm-2s-1)
Irradiated sample
１kGy
Not irradiated
ref. sample
K. Kawade et al., JINST, 6, T09004, 2011
τ~4.2h recovery
 No decrease up to 1 MGy
 +20% increase over 1 kGy (τ=4.2h recovery)
 2 kGy is expected for 350nb-1 @ 14TeV pp)
Global LHCf physics program
LHCf measurement for p-Pb interactions at 3.5TeV proton energy
could be easily and finely integrated in the LHCf global campaign.
Period
Type
Beam
energy
LAB proton
Energy (eV)
Detector
2009
p-p
450+450 GeV
4.3 1014
Arm1+Arm2
2009/2010
p-p
3.5+3.5 TeV
2.6 1016
Arm1+Arm2
2013
p – Pb
3.5 TeV
proton E
1016
Arm2
2014
p-p
7+7 TeV
1017
Arm1+Arm2
upgraded
Proton-remnant side – photon spectrum
Small tower
Big tower
Proton-remnant side – neutron spectrum
Small tower
35% ENERGY
RESOLUTION IS
CONSIDERED IN
THESE PLOTS
Big tower
Proton remnant side –
Invariant cross section for isolated g-rays
What LHCf can measure in the p+Pb run (2)
Study of the Nuclear Modification Factor
Nuclear
Modification
Factor
measured at RHIC (production of
p0): strong suppression for small pt
at <>=4.
Phys. Rev. Lett. 97 (2006) 152302
LHCf can extend the measurement
at higher energy and for >8.4
Very important for CR Physics
Lead-remnant side – multiplicity
Please remind that EPOS does not consider Fermi motion and Nuclear Fragmentation
Small tower
g
n
Big tower
… and required statistics to complete the
p/Pb physics run
 Minimum required number of collision: Ncoll = 108
(factor 10 more statistics wrt shown plots)
 Integrated luminosity Lint = 50 mb-1
 2106 single photons expected on p-remnant side
 35000 p0 expected on same side
 Assuming a pessimistic scenario with luminosity
L = 1026 cm-2s-1 :
 Minimum running time for physics
t = 140 h (6 days)