1. Latest results from LHCf on very forward particle production at LHC
Oscar Adriani
University of Florence & INFN Firenze
Latest results from the LHC
CERN, July 12th, 2012

2. Physics Motivations Impact on High Energy Cosmic Ray Physics
O. Adriani Latest results from LHCf Cern, July 12, 2012

3. The Cosmic Rays energy spectrum
1 particle/m2/sec
Direct Measurement by Balloon and Satellite
1 particle/m2/year
Air shower technique
1 particle/km2/year
1 particle/km2/century

4. Indirect measurement of cosmic rays
Composition and energy of cosmic rays affect the generation of Extended Air Showers
Precise understanding of high-energy cosmic ray should be achieved with the indirect measurement technique
Comparison between the MC simulation of EAS and observation is necessary to infer the information on the primary CR from the measurement of the shower
Largest systematic uncertainty of indirect measurement is caused by the finite understanding of the hadronic interaction of cosmic ray in atmosphere γ p Fe
Altitude [km]
1. 10^14eV以上ではindirect method以外に方法が無い。
2. 見られるのはair showerの情報のみ→best-matched MCが宇宙線の情報になる。
3. 間にあるhadronic interactionを精密に理解する。
Radius [km]
O. Adriani Latest results from LHCf Cern, July 12, 2012

5. Example I: the VHECR Energy spectrum
Auger and Telescope Array are currently taking data
Auger has
the highest statistics.
Two kinks: the ankle and the GZK cutoff
Both Auger and TA spectra shows two kinks… BUT…
The fluxes are significantly different!
Energy scale problem?  Precise knowledge of the hadronic interaction mechanism at VHE is necessary
O. Adriani Latest results from LHCf Cern, July 12, 2012

6. Example II: Chemical Composition
The Chemical composition can be inferred from the depth of the maximum of the shower (Xmax)
Shower depth [g/cm2]
Proton
Iron
Gamma-ray
Xmax
E=1019eV
BUT….
The results depend on the precise knowledge of the hadronic interaction mechanism!!!!!
Auger
Model uncertainty
PROTON TA
IRON 6
O. Adriani Latest results from LHCf Cern, July 12, 2012

7. Example II: Chemical Composition
The Chemical composition can be inferred from the depth of the maximum of the shower (Xmax)
Shower depth [g/cm2]
Proton
Iron
Gamma-ray
Xmax
E=1019eV
BUT….
The results depend on the precise knowledge of the hadronic interaction mechanism!!!!!
Both in the energy determination and Xmax prediction MC simulations are used, and are one of the greater sources of uncertainty.
Experimental tests of hadron interaction models are necessary!  LHCf
Auger
Model uncertainty
PROTON TA
IRON 7
O. Adriani Latest results from LHCf Cern, July 12, 2012

8. Why LHC?
The experimental set-up

9. The Cosmic Ray spectrum
LHC Energy range is very interesting for Cosmic Ray Physics!
14TeV
0.9TeV
7TeV
Direct
Indirect
O. Adriani Latest results from LHCf Cern, July 12, 2012

10. Air Shower development
Total cross section
Large σ  rapid development
Small σ  deep penetrating
Multiplicity (N)
Large N  rapid development large number of muons
Small N  deep penetrating small number of muons
Inelasticity(k)/Secondary spectra
Large k, Softer spectra  rapid development
Small k, harder spectra  deep penetrating
O. Adriani Latest results from LHCf Cern, July 12, 2012

11. LHC experiments
Whole pseudo-rapidity is covered by the different LHC experiments
Key parameters
for air shower developments
Total cross section ↔ TOTEM, ATLAS, CMS
Multiplicity ↔ Central detectors
Inelasticity/Secondary spectra ↔ Forward calorimeters LHCf, ZDCs
R. Orava, (2005)
O. Adriani Latest results from LHCf Cern, July 12, 2012

12. LHCf: location and detector layout
INTERACTION POINT
IP1 (ATLAS)
Detector II
Tungsten
Scintillator
Silicon mstrips
Detector I
Scintillating fibers
140 m n π0 γ
8 cm
6 cm
Front Counter
44 X0,
1.6 lint
Arm#1 Detector
20mmx20mm+40mmx40mm
4 X-Y SciFi tracking layers
Arm#2 Detector
25mmx25mm+32mmx32mm
4 X-Y Silicon strip layers
Expected Performance
Energy resolution
< 5% for g
~30% for neutrons
Position resolution ~ 100μm
O. Adriani Latest results from LHCf Cern, July 12, 2012

13. What LHCf can measure? Energy Flux @14TeV Low multiplicity !!
Energy spectra and Transverse momentum distribution of photons, neutrons and p0 in the pseudorapidity region h > 8.4
Energy
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.
simulated by DPMJET3
Low multiplicity !!
High energy flux !!
O. Adriani Latest results from LHCf Cern, July 12, 2012

14. What LHCf can measure?
Energy spectra and Transverse momentum distribution of photons, neutrons and p0 in the pseudorapidity region > 8.4
Energy
Very precisely measure the highest energy LHC photons (up to 7 TeV) with the smallest LHC detector (~few cm2)
The experimental challenge:
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.
simulated by DPMJET3
Low multiplicity !!
High energy flux !!
O. Adriani Latest results from LHCf Cern, July 12, 2012

15. LHCf main physics results
“Measurement of zero degree single photon energy spectra for √s = 7 TeV proton-proton collisions at LHC“
PLB 703 (2011) 128
“Measurement of zero degree single photon energy spectra for √s = 900 GeV proton-proton collisions at LHC“
Submitted to PLB
CERN-PH-EP
“Measurement of forward neutral pion transverse momentum spectra for √s = 7TeV proton-proton collisions at LHC“
Submitted to PRD
CERN-PH-EP
O. Adriani Latest results from LHCf Cern, July 12, 2012

16. Inclusive g spectrum at 900 GeV
Data
DPMJET 3.04
SIBYLL 2.1
EPOS 1.99
PYTHIA 8.145
QGSJET II-03
MC/Data
Gray hatch : Systematic Errors
O. Adriani Latest results from LHCf Cern, July 12, 2012

17. Inclusive g spectrum at 7 TeV
Gray hatch : Systematic Errors
Magenta hatch: MC Statistical errors
Data
MC/Data
O. Adriani Latest results from LHCf Cern, July 12, 2012

18. Inclusive g spectrum at 7 TeV
Gray hatch : Systematic Errors
Magenta hatch: MC Statistical errors
Data
None of the Models agrees with the data!
These measurement are important to improve the hadronic interaction models in the high energy region
MC/Data
O. Adriani Latest results from LHCf Cern, July 12, 2012

19. Comparison between 900 GeV and 7 TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
small-η = Large tower
big-η =Small tower
O. Adriani Latest results from LHCf Cern, July 12, 2012

20. Comparison between 900 GeV and 7 TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
small-η = Large tower
big-η =Small tower
900GeV vs. 7TeV with the same PT region
900 GeV
Small+large
tower
O. Adriani Latest results from LHCf Cern, July 12, 2012

21. Comparison between 900 GeV and 7 TeV spectra
Coverage of the photon spectra
in the plane Feynman-X vs PT
Normalized by the number of entries in XF > 0.1
No systematic error is considered in both collision energies.
XF spectra : 900GeV data vs. 7TeV data
Good agreement of XF spectrum shape between 900 GeV and 7 TeV.  weak dependence of <pT> on ECMS
Preliminary
Data 2010 at √s=900GeV
(Normalized by the number of entries in XF > 0.1) Data 2010 at √s=7TeV (η>10.94)
small-η = Large tower
big-η =Small tower
900GeV vs. 7TeV with the same PT region
900 GeV
Small+large
tower
O. Adriani Latest results from LHCf Cern, July 12, 2012

22. 7 TeV π0 analysis
Mass, energy and transverse momentum are reconstructed from the energies and impact positions of photon pairs measured by each calorimeter
I.P.1 
1(E1)
2(E2)
140m R
O. Adriani Latest results from LHCf Cern, July 12, 2012

23. p0 Data vs MC: PT spectra for different rapidity bins
O. Adriani Latest results from LHCf Cern, July 12, 2012

24. p0 Data vs MC
dpmjet 3.04 & pythia 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.
O. Adriani Latest results from LHCf Cern, July 12, 2012

25. <PT> for different y bins
π0 analysis at √s=7 TeV
Submitted to PRD (arXiv: ).
pT spectra vs best-fit function
Average pT vs ylab
<PT> for different y bins
PLB (1990)
YBeam=6.5 for SPS
YBeam=8.92 for7 TeV LHC
ylab = ybeam - y
Systematic uncertainty of LHCf data is 5%.
Comparison with the UA7 data (√s=630GeV) and MC simulations (QGSJET, SIBYLL, EPOS).
Two experimental data mostly appear to lie along a common curve → No evident dependence of <pT> on ECMS.
Smallest dependence on ECMS is found in EPOS and it is consistent with LHCf and UA7.
Large ECMS dependence is found in SIBYLL
O. Adriani Latest results from LHCf Cern, July 12, 2012

26. What’s next and … conclusions …
O. Adriani Latest results from LHCf Cern, July 12, 2012

27. LHCf Future PLANS: Ion run and 14 TeV
2010
2011/2012
2013
2014
LHC
14TeV
7TeV
shutdown
Jul
Detector upgrade
Re-install
Re-install
LHCf I
LHCf-HI
LHCf II
2013: p-Pb runs
Interest in Ion runs
Physics case study well motivated
We will reinstall one ARM on p-remnant side during p-Pb run (beginning of 2013)
2014: 14 TeV p-p runs
Necessary to complete the LHCf physics program
The highest Elab will be reached (1017 eV), to go closer to the VHECR region n
Pb –remnant side 
p –remnant side
O. Adriani Latest results from LHCf Cern, July 12, 2012

28. Conclusions
LHCf represent a very interesting and useful link between accelerator physics and cosmic ray physics
The experiment has been carefully designed to precisely measure the highest energy LHC photons (up to 7 TeV), despite being the smallest LHC detector (few cm2)
Nice physics results have been performed both on g and p0
LHCf results have shown to be very useful for the very high energy cosmic rays models developer to improve their codes
p/Pb run in 2013 and 14 TeV p/p run in 2014 are the next important steps
O. Adriani Latest results from LHCf Cern, July 12, 2012

29. Backup slides

30. What LHCf can measure in the p+Pb run E, pT,  spectra of neutral particles
We are simulating protons with energy Ep = 3.5 TeV
Energy per nucleon for ion is
“Arm2” geometry considered on both sides of IP1 to study both p- remnant side and Pb-remnant side
No detector response introduced yet (only geometrical considerations and energy smearing)
Results are shown for DPMJET and EPOS 1.99, 107 events each
“Pb-remnant side”
“p-remnant side”
140 m
140 m
p-beam
Pb-beam
O. Adriani Latest results from LHCf Cern, July 12, 2012

31. Proton remnant side – Photon spectra
O. Adriani Latest results from LHCf Cern, July 12, 2012

32. Proton remnant side - Neutron spectra
O. Adriani Latest results from LHCf Cern, July 12, 2012

33. Lead-remnant side – multiplicity Please remind that EPOS does not consider Fermi motion and Nuclear Fragmentation
Small tower
Big tower  n
O. Adriani Latest results from LHCf Cern, July 12, 2012

34. 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.
LHCf can extend the measurement at higher energy and for >8.4
Very important for CR Physics
Phys. Rev. Lett. 97 (2006)
O. Adriani Latest results from LHCf Cern, July 12, 2012

35. Muon excess at Pierre Auger Obs.
Auger hybrid analysis
event-by-event MC selection to fit FD data (top-left)
comparison with SD data vs MC (top-right)
muon excess in data even for Fe primary MC
EPOS predicts more muon due to larger baryon production
=> importance of baryon measurement
Pierre Auger Collaboration, ICRC 2011 (arXiv: )
Pierog and Werner, PRL 101 (2008)
O. Adriani Latest results from LHCf Cern, July 12, 2012

36. Neutron at LHCf phase-space
By Tanguy Pierog,
Modelists waiting for LHCf!!
O. Adriani Latest results from LHCf Cern, July 12, 2012

37. Arm1 vs Arm2 comparison
O. Adriani Latest results from LHCf Cern, July 12, 2012

38. π0 spectrum and air showers
π0 spectrum at Elab = 1017eV
DPMJET3 original
Artificial modification
Longitudinal AS development
<Xmax>=718 g/cm2
<Xmax>=689 g/cm2
Vertical Depth (g/cm2)
Artificial modification of meson spectra (in agreement with differences between models)
D<Xmax(p-Fe)> ~ 100 g/cm2
Effect to air shower ~ 30 g/cm2
AUGER, ICRC 2011
O. Adriani Latest results from LHCf Cern, July 12, 2012

39. LHCf operations @900 GeV & 7 TeV
With Stable Beam at 900 GeV Dec 6th – Dec 15th 2009
With Stable Beam at 900 GeV May 2nd – May 27th 2010
With Stable Beam at 7 TeV March 30th - July 19th 2010
We took data with and without 100 μrad crossing angle for different vertical detector positions
Shower
Gamma
Hadron
Arm1
46,800
4,100
11,527
Arm2
66,700
6,158
26,094
Shower
Gamma
Hadron π0
Arm1
172,263,255
56,846,874
111,971,115
344,526
Arm2
160,587,306
52,993,810
104,381,748
676,157
O. Adriani Latest results from LHCf Cern, July 12, 2012

40. p0 reconstruction 1(E1)  An example of p0 events
measured energy Arm2
25mm
32mm
preliminary
Silicon strip-X view
I.P.1 
1(E1)
2(E2)
140m R
Reconstructed Arm2
p0’s are the main source of electromagnetic secondaries in high energy collisions.
The mass peak is very useful to confirm the detector performances and to estimate the systematic error of energy scale.
O. Adriani Latest results from LHCf Cern, July 12, 2012

41. h Mass Arm2 detector, all runs with zero crossing angle
True h Mass: MeV
MC Reconstructed h Mass peak: ± 1.0 MeV
Data Reconstructed h Mass peak: ± 1.8 MeV (2.6% shift)
O. Adriani Latest results from LHCf Cern, July 12, 2012

42. π0 analysis at √s=7TeV Type-I Type-II Small angle Large angle large BG
Submitted to PRD (arXiv: ).
Type-I
Type-II
Large angle
Simple
Clean
High-stat.
Small angle
large BG
Low-stat. , but can cover
High-E
Large-PT
Type-I LHCf-Arm1
Type-II LHCf-Arm1
LHCf-Arm1 Data 2010
Preliminary
Type-II at large tower BG
Type-II at small tower
Signal
O. Adriani Latest results from LHCf Cern, July 12, 2012