Forward photon spectrum in 7 TeV pp collisions measured by the LHCf - - PowerPoint PPT Presentation

Forward photon spectrum in 7 TeV pp collisions measured by the LHCf experiment

Koji Noda (INFN Catania)

• n behalf of the LHCf collaboration

Workshop on Multi-Parton Interactions at the LHC 25 Nov. 2011, DESY, Hamburg

Contents

• “A collider experiment for cosmic ray physics”
• LHCf detector and operation
• Analysis for single photon spectra at 7 TeV
• Discussions & prospects
• Summary

M Nagano

New Journal of Physics 11 (2009) 065012

LHC SPS

AUGER

Cosmic ray spectrum LHC SPS

(UA7)

cm energy at LHC (7+7TeV) <=> 10^17eV CR (fixed target) >10^15eV: detected with air-showers, but many unknowns

Tevatron Tevatron

Very-high-energy cosmic ray spectrum

4

• 1. Inelastic cross section
• 2. Forward energy spectrum

If large k rapid development If small k deep penetrating If large σ rapid development If small σ deep penetrating

• 4. 2ndary interactions
• 3. Inelasticity k

(1-Eleading)/E0

If softer rapid development If harder deep penetrating

Air-shower development

5

Impact of air-shower development uncertainty on E-scale & composition

• Atm. depth

#of particles

AUGER alt.

SD E-scale error

J.Knapp Astropart. Phys.19 (2003) 77

• E-scale uncertainty
• Surface detector: large

(AGASA claims 20%)

• Florescence: OK (a few %),

but FD  SD problem

• Composition uncertainty

AUGER ICRC09 Composition error

Model dependence must be decreased by measurements!

What should be measured?

6

Multiplicity Energy Flux All particles neutral

Most of the energy flows into very forward

sqrt(s)=14TeV Elab=1017eV multiplicity and energy flux at LHC 14TeV collisions pseudo-rapidity; η= -ln(tan(θ/2))

7

Recent input from LHC data

Charged hadron multiplicity Inelastic cross section Missing part: spectra of forward neutral particles

8

K.Fukatsu, T.Iso, Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, Y.Muraki, T.Sako, K.Suzuki, K.Taki Solar-Terrestrial Environment Laboratory, Nagoya University, Japan H.Menjo Kobayashi-Maskawa Institute, Nagoya University, Japan K.Yoshida Shibaura Institute of Technology, Japan K.Kasahara, Y.Shimizu, T.Suzuki, S.Torii Waseda University, Japan T.Tamura Kanagawa University, Japan M.Haguenauer Ecole Polytechnique, France W.C.Turner LBNL, Berkeley, USA O.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, P.Papini, S.Ricciarini, G.Castellini INFN, Univ. di Firenze, Italy K.Noda, A.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, Spain A-L.Perrot CERN, Switzerland

The LHCf Collaboration

Detector Location

9

140m

LHCf Detectors

10

Arm#1 Detector 20mmx20mm+40mmx40mm 4 XY SciFi+MAPMT Arm#2 Detector 25mmx25mm+32mmx32mm 4 XY Silicon strip detectors

Imaging sampling shower calorimeters  Two independent calorimeters in each detector (Tungsten 44r.l., 1.6λ, sampling with plastic scintillators)  4 position sensitive layers distributed in the calorimeters

Detector photos

Arm#1 Detector Arm#1 Detector Arm#2 Detector Arm#2 Detector 90mm 90mm 2 9 m m 2 9 m m

12

ATLAS & LHCf

12

13

ATLAS & LHCf

13

Event category of LHCf

14

Single hadron event Pi-zero event (photon pair) Single photon event

Expected Results at 14 TeV Collisions

(MC assuming 0.1nb-1 statistics)

Detector response not considered

15 Single photon π0 Single photon at different η Single neutron

16

Brief history of LHCf

• May 2004 LOI
• Feb 2006 TDR
• June 2006 LHCC

approved

Jan 2008 Installation Aug 2007 SPS beam test Sep 2008 1st LHC beam Jul 2006 Assembling Mar 2010 1st 7TeV run Dec 2009 1st 900GeV run Jul 2010 Detector removal

Summary of Operations in 2009 and 2010

With Stable Beam at 900 GeV

Total of 42 hours for physics About 100 k shower events in Arm1+Arm2

With Stable Beam at 7 TeV

Total of 150 hours for physics with different setups

Different vertical position & with beam crossing angle for a wide kinematical range

~ 400 M shower events in Arm1+2 ~ 1 M π0 events in Arm1+2

17

Arm1 π0 stat.

Arm1 π0 events

Status

Completed program for 900 GeV and 7 TeV Removed detectors from tunnel in July 2010 Post-calibration beam test in October 2010 Upgrade on-going to more rad-hard detectors for 14TeV in 2014

EM shower and π0 example

• neutral pion candidate
• 599GeV & 419GeV photons in 25mm

and 32mm tower, respectively

• M = θ x sqrt(E1xE2)

18

Event sample by Arm2

Longitudinal development Lateral development

Silicon X Silicon Y Small Cal. Large Cal. Invariant mass of photon pairs

Publication (w/ MC) coming soon

‘new’ neutral pion analysis

Original Idea New Analysis!

Type-II BG reduction still to be optimized

20

• DATA

▫ 15 May 2010 17:45-21:23 (#Fill 1104), Low Luminosity (6.5-6.3)x1028cm-2s-1, no beam crossing angle ▫ 0.68 nb-1 for Arm1, 0.53nb-1 for Arm2

• MC

▫ DPMJET3.04, QGSJETII03, SYBILL2.1, EPOS1.99, PYTHIA 8.145 ▫ 107 inelastic p-p collisions by each model

• Analysis

▫ Particle identification using longitudinal shower development ▫ multi-hit rejection ▫ Acceptance cut: two common η ranges (small tower: η>10.94, large: 8.81<η<8.9) = No correction for geometrical acceptance ▫ systematic errors

Single photon energy spectra

• O. Adriani et al., PLB703 (2011) 128-134

Arm1 Arm2

Particle ID

EM and hadronic showers are separated with a method based on a difference of the longitudinal shower development

21 # Response of detectors to hadrons is in study. Nphoton/Nhadron ratio will give a good information for model discrimination For other details in the photon analysis, please refer to the publication:

• O. Adriani et al., PLB703 (2011) 128-134

beam direction

Obtained photon spectra

 Normalized by number of inelastic collisions Nine = σine * ∫Ldt  σine = 71.5mb assumed; consistent with recent ATLAS result (c.f. 73.5±0.6. mb by TOTEM )

22

=> Combined & compared with MC models

+1.8

• 1.3

Comparison between Models

DPMJET 3.04 SIBYLL 2.1 EPOS 1.99 PYTHIA 8.145 QGSJET II-03

Gray hatch : Systematic Errors Magenta hatch: MC Statistical errors

• None of the models nicely describe the LHCf data in the

whole energy range (100 GeV – 3.5 TeV).

• Very big discrepancy in the high energy region
• Significant improvement of the models is possible by model developers

23

Impact on CR physics

Artificial modification of meson spectra -> How does it affect? ∆ Xmax (p-Fe) ~ 100 g/cm2 The effect ~30 g/cm2

24

Discussions & prospects

• LHCf for multi-parton physics?

▫ very forward = low-x parton scattered by high-x parton ▫ In small-x, gluon is dominant, but its density begins to saturate with increasing energy

soft hard semi-hard reality

How much is the non-linear saturation effect?

Discussions & prospects

• LHCf for multi-parton physics?

▫ very forward = low-x parton scattered by high-x parton ▫ In small-x, gluon is dominant, but its density begins to saturate with increasing energy

soft hard semi-hard reality

How much is the non-linear saturation effect?

• What’s next to be analyzed or measured?

▫ neutral pion: already mentioned ▫ 900GeV photon: E-scale of the non-linear effect? ▫ 7 TeV photon Pt: support for the photon spectrum result ▫ 7 TeV hadron spectra: inelasticity for CR physics ▫ pA run (in 2012): larger effect? ▫ 14 TeV run (in 2014): larger effect, but upgrade needed

Model dependence would be larger than in 7 TeV pp run We hope LHCf will come back to CERN in 2012

Studies for pA run (foreseen in 2012)

photon spectra by Arm2 in p-Pb run (p-remnant side)

Upgrade for 14TeV

for rad-hardness for improvement of energy reconstruction

Silicon layer positions in Arm2 detector

X,Y X,Y X,Y X,Y

X,Y X,Y X X Y Y

Energy reconstruction with the Si layers is also useful

higher luminosity is expected in the 14TeV runs

28

Kawade+ (2011)

MC

E rec. only with Si

Method for the obtained data:

▫ Correction esp. for high-E events (fitting with a peak shape) ▫ ADC count -> energy deposit gain (by test beam)

• > incident energy reconstruction func. (by MC)

E reconstruction

• nly with Si data:

mean ~5%, E reso. ~15%

(~10% will be achieved with the upgrade)

E only by Si vs. E by scinti. (w/ corr.)

• scinti. energy (GeV)

E resolution 0.9~1.1TeV

# This is a good news for separation of multi-hit events (type-II neutral pions)

Si data

Summary

• LHCf: a collider experiment for cosmic ray physics
• DAQ for 900GeV & 7 TeV pp collision completed
• Single photon spectra show a discrepancy from

the MC simulation models

• It will be a guideline for improvement of the non-

linear effect implementation in the models

• Now following analyses for pi-zero & 900GeV

photon spectra etc. are underway

• Studies for pA run in 2012 and upgrade works for

14 TeV pp run are also on-going

backup

33 By Ostapchenko

Physics of MC Physics of MCs s (

(K. Werner, EDS09, CERN)

Nonlinear effects in MCs Nonlinear effects in MCs

all slides are by

• K. Werner, EDS09, CERN

Non-linear effects are implemented in a phenomenological manner

FrontCounter

• 2 fixed Front Counters

installed in front of Arm1 and Arm2

• They will not move with

Arm1 and Arm2

• segmented in 2 x- and 2 y-

slices

• Very useful to check the

beam quality

Alessia Tricomi University and INFN Catania EPS 09, Krakow 16-22 July 2009

Acceptance

38

π0

Photon at √s =14TeV pp collision

39

900GeV spectra

• Eff. uncorrected, stat. error only

Normalized by total # of events.

Gamma-ray like Gamma-ray like Hadron like Hadron like Gamma-ray like Gamma-ray like Hadron like Hadron like

Arm1 Arm1 Arm2 Arm2

Preliminary Preliminary Now refined analysis for publication is ongoing

Q^2 1/x

Very forward

semi-hard hard soft

increasing E (w/ fixed η)