LHCf Status
Oscar Adriani
CSN1,MIlano, 26 Marzo 2013
Summary of operations in end 2012beginning 2013 (after the Torino meeting)
 Arm2 has been re-installed in the TAN region in December
2012
 January-February 2013: p/Pb run
 Arm2 will be removed from the TAN in April 2013
 The Arm2 upgrade for the 13 TeV run will be done in Florence
in 2013 in strict collaboration with Japanese colleagues
 Some more details will be given in the next slides
Re-Installation issues
 Arm2 has been successfully re-installed in the TAN during the
technical stop foreseen at the end of the p/p run 
December 18th
 We have modified the LHCf support structure and cabling to
significantly reduce the installation required time
 Mechanical survey has been done in 2 steps:
 Internal LHCf survey on ground
 LHCf survey wrt to LHC: done on December 18th in the TAN area
 No big problem of radiation, the installation was completely
safe (Thanks to Raffaello and Sako!!!)
Discussions and agreements with ATLAS (I)
 ATLAS trigger can not be sent to LHCf due to timing problem
 LHCf Level1 Trigger signal has been sent to ATLAS for the
whole p/Pb running period
 ATLAS has properly prescaled the LHCf trigger signal
 Prescaling factor depend on the running conditions
 LHCf has recorded in the data stream all the counters and has
used all the signals necessary to off-line identify the common
events
 Event Counter Reset
 Atlas L1ID
 Bunch ID
Discussions and agreements with ATLAS (II)
Proton remnant side –
Invariant cross section for isolated g-rays
Using only the LHCf informations
What happens if know the Impact Parameter?
Ideal case, assuming that we can
precisely know the Impact
Parameter b (in fm) on event by
event basis
What happens if know the Impact Parameter?
What happens if know the Impact Parameter?
What happens if know the Impact Parameter?
What happens if know the Impact Parameter?
Combination of different impact parameter bins
What happens with LHCf on Pb remnant
side?
Nominal vertical position (Dy=0 cm)
Shifting up by Dy= +2.5 cm
The small calorimeter tower
remain in the region not
screened by the narrow elliptical
shape of the beam pipe at D1
magnet  We can take good
data with reasonable number of
hits!
LHCf operation in p – Pb runs at √sNN= 5
TeV
Proton remnant side
IP2
Pb
IP1
Arm2
p
IP8
Lead remnant side
IP2
p
IP1
Arm2
Pb
IP8
LHCf operation in p – Pb runs at √sNN= 5
TeV
200 Millions triggered events!!!!
p-remnant
side
#Events (Millions)
Pb-remnant
side
Beam reversal
20 Jan
27 Jan.
01 Feb.
Summary of LHCf p-Pb runs
 L = 0.5x1029 – 1x1029cm-2s-1
 b* =0.8m, 145mrad crossing angle
 Not good for LHCf….
 We didn’t succeed to get a dedicated high b* run due to the lack of
time
 338p+338Pb bunches (min.DT=200ns), 296 colliding at IP1
 10-20kHz trig rate downscaled to ~700Hz
 20-40Hz ATLAS common trig
 Coincidence operation was successful!!!
 Data both at p-side (20Jan-1Feb) and Pb-side (1fill, 4Feb)
Operation at Pb-remnant side
IP2
p
IP1
Arm2
Pb
IP8
+4.0MC
cm(Pb-remnant)
shift from beam spo
3.5cm,
4.0cm
A high multiplicity event (Pb-side)
Proton-Proton Collision at √s = 2.76 TeV
 We also profited of the ‘calibration’ run at √s
= 2.76 TeV that has been done following the
ATLAS and CMS requests
 4 hours operation on 14 Feb. 2013 successfully
done.
These data will allow a better study of the
energy Scaling by comparing different c.m.
energy (0.9 TeV, 2.76 TeV, 7 TeV, 13 TeV)
Data list of LHCf
With ATLAS
γ, n
π0
p-p, √s=900GeV, 2010
✔
(event flags)
p-p, √s=2.76TeV, 2013
✔
LHCf triggers 
p-p, √s=7TeV, 2010
✔
✔
(event flags)
p-p, √s=13 TeV, (2015)
✔
✔
LHCf triggers 
p-N,O, (>2019)
✔
✔
LHCf triggers 
p-Pb, √sNN=5TeV, 2013
✔
✔
LHCf triggers 
p-p 400GeV, p-A
at RHICH (???)
✔
✔
 PHENIX,
STAR
Black:
completed
operations
Orange:
Future
operations
Playing a game with air shower development:
effect of forward meson spectra
• DPMJET3 always overpredicts production
• Filtering DPMJET3 mesons
• according to an empirical probability function,
divide mesons into two with keeping pT
• Fraction of mesons escape out of LHCf acceptance
• This process
• Holds cross section
• Holds elasticity/inelasticity
• Holds energy conservation
• Changes multiplicity
• Does not conserve charge event-by-event
pT
E
E
2
1
E=E1+E2
xF = E/E0
xF = E/E0
An example of filtering
photon spectrum
π0 spectrum
Apart from this ‘game’ we are in
strict contacts with model developers
to help them improving their codes.
Few dedicated workshops have been
organized to put theorists and
experimentalists in contact
DPMJET3+filter
2.5x1016 eV proton
~30g/cm2
π0 spectrum and air shower
100 g/cm2
30 g/cm2
Vertical Depth (g/cm2)
AUGER, ICRC 2011
Other analyses and future activities….
 Joint analysis with ATLAS … data ready
 14 TeV p-p in 2015 … detector upgrade on going
 Neutron spectra in 7TeV p-p … analysis on going
 Light nuclei at LHC, RHIC???
… possibility in discussion
LHCf preparation for the 14 TeV p-p run
 Calorimeter radiation hardening by replacing plastic scintillator with GSO
 Production and laboratory tests of the new scintillators in Japan is
finished for Arm1 and in progress for Arm2
 Beam test at Ion facility (HIMAC) for Arm1 has been done in June 2012
 Arm1 has been re-assembled in Florence starting from end of
June 2012
 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
 Test Beam at LNS for the absolute energy calibration of the silicon system
is being requested
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 Spectra at 7 TeV pp (models)
Model predictions
Model predictions
smeared taking into
account the LHCf energy
resolution
Life is not easy…..
1 TeV neutrons
simulated with 2
different hadronic
interaction models
used in the
detector
simulation
Other possibile future runs?
 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 is under discussion…
 Please stand by a little bit to see how things are evolving!!!!
Il calcolo per LHCf
 A settembre la CSN1 ci ha ‘suggerito’ di muoversi nella direzione di utilizzare
le risorse di calcolo del CNAF (nonostante le richieste estremamente
limitate di 15 kEuro)
 In questi mesi, con l’aiuto di Vincenzo Vagnoni e con il supporto di Luca
Dell’Agnello, abbiamo sistemato le infrastrutture tecniche necessarie per:
 Generazione (per almeno 4 modelli di interazione adronica)
 End2End (trasporto beam-pipe)
 DoubleArm (simulazione del rivelatore)
 Compilatori, spazio di storage, creazione degli account e delle code per I
jobs, etc.
 Il sistema ora e’ ‘pronto per partire’
Necessita’
 Almeno 4x107 eventi
 Generazione:
 35 kB/event
 0.1 sec/event
 Trasporto:
 100-500 kB/event
 100-500 sec/event
 Simulazione:
 20 kB/event
 10 sec/event
 CPU:
 Almeno 4x109 secondi estendibili a 1.3x1010 sec se ci fosse la
necessità di avere 108 eventi per un modello
 Storage:
 20-30 TB
Come sta andando
 Siamo in contatto con CNAF per finire di risolvere i problemi
tecnici rimasti
 La procedura e’ stata faticosa, ma alla fine siamo (quasi)
arrivati….
 Non mi e’ chiaro come ora sia necessario procedere con la
commissione per pagare le risorse CNAF….
Conclusions
 Re-installation in the tunnel and p/Pb run went very smooth
 p/Pb and neutron analyses are on-going
 Atlas joint analysis is ready to start
 Arm2 upgrade will be completed in 2013
 Computing system at CNAF is available
 Ready to take data at 14 TeV
 And…. Possible Light Ions runs at RHIC/LHC are under investigation
 Next week we will have the LHCf meeting in Nagoya
Spares slides
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
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)
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
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
π0 results: Data vs MC
π
0 results: Data/MC
Submitted to PRD (arXiv:1205.4578).
<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
Comparison wrt MC Models at 900 GeV
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 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