Forward particle production measured by LHCf;

testing hadronic interaction models for CR physics

Takashi SAKO(Solar-Terrestrial environment Laboratory/Kobayashi-

Maskawa Institute, Nagoya University, Japan)On behalf of the LHCf Collaboration

11-Feb-2013 IV Workshop on Air Shower Detection at High Altitude@Napoli

Forward particle production measured by LHCf;

testing hadronic interaction models for CR physics

Takashi SAKO(Solar-Terrestrial environment Laboratory/Kobayashi-

Maskawa Institute, Nagoya University, Japan)On behalf of the LHCf Collaboration

21-Feb-2013 IV Workshop on Air Shower Detection at High Altitude@Napoli

Outline

• Quick reminder for the CR and interaction• Important collider observables• The LHCf experiment

– Experimental setup and status– Results from 900GeV and 7TeV p-p collisions– Impact on air shower– Future

• Summary

3

CR and Interaction

4

5

Uncertainty in hadronic interaction

PROTON

IRON

10191018

0g/cm2

Xmax

Proton shower and nuclear shower of same total energy

Pierre Auger Observatory

Deep in the atmosphere

Players: EPOS, QGSJET, SIBYLL, DPMJET models

6(Kampert and Unger, Astropart. Phys., 2012)

Lower energy also… QGS1 QGSII

SIBYLL EPOS

Collider observables

7

8

Leading baryons Multi meson production

What to be measured at accelerators?

proton / neutron

π0

π+

π-

γ

1. Inelastic cross section（ interaction mean free path）

3. Nuclear effect

elasticity (Ebaryon/E0)baryon spectrum

inelasticity (Emeson/E0= 1-elasticity)multiplicitymeson spectrum

2. Particle production

Note: √s=14TeV <=> Elab=1017eV

Where 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 particles produced into central,Most of the energy flows into forward 9

10

result @ 7TeV

The TOTEM Collaboration, CERN-PH-EP-2012-353

R.Ulrich et al., PRD, 83 (2011) 054026

Before LHC

After LHC

multiplicity@central

11

D.D’Enterria et al., Astropart. Phys., 35 (2011) 98-113

Forward Energy Flow (Hadronic Forward Calorimeter)

12The CMS Collaboration, JHEP, 11 (2011) 148

LHCf

13

T.Iso, Y.Itow, K.Kawade, Y.Makino, K.Masuda, Y.Matsubara, E.Matsubayashi, G.Mitsuka, Y.Muraki, T.Sako

Solar-Terrestrial Environment Laboratory, Nagoya University, Japan

H.Menjo Kobayashi-Maskawa Institute, Nagoya University, Japan K.Yoshida Shibaura Institute of Technology, JapanK.Kasahara, Y.Shimizu, T.Suzuki, S.Torii Waseda University, JapanT.Tamura Kanagawa University, JapanM.Haguenauer Ecole Polytechnique, FranceW.C.Turner LBNL, Berkeley, USAO.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi, P.Papini, S.Ricciarini, G.Castellini INFN, Univ. di Firenze, ItalyA.Tricomi INFN, Univ. di Catania, Italy J.Velasco, A.Faus IFIC, Centro Mixto CSIC-UVEG, SpainA-L.Perrot, D.Pfeiffer CERN, Switzerland

The LHCf collaboration

The LHC forward experiment

15

ATLAS

140m

LHCf Arm#1

LHCf Arm#2

Two independent detectors at either side of IP1 (Arm#1, Arm#2 )

Charged particles (+)Beam

Charged particles (-)

Neutral particles

Beam pipe

96mm

• All charged particles are swept by dipole magnet• Neutral particles (photons and neutrons) arrive at LHCf• 0 degree is covered

LHCf Detectors

Arm#1 Detector20mmx20mm+40mmx40mm4 XY SciFi+MAPMT

Arm#2 Detector25mmx25mm+32mmx32mm4 XY Silicon strip detectors

Imaging sampling shower calorimeters Two calorimeter towers in each of Arm1 and Arm2 Each tower has 44 r.l. of Tungsten,16 sampling scintillator and 4

position sensitive layers

16

17

Which E-pT range LHCf sees ?

pp 7TeV, EPOS

photons p0 (Arm1)

Summary of 2009-2010 run and current status　With Stable Beams at √s = 900 GeV

Total of 42 hours for physics About 105 shower events in Arm1+Arm2

With Stable Beams at √s = 7 TeV (Elab = 2.5x1016 eV) Total of 150 hours for physics with different setups

Different vertical position to increase the accessible kinematical range Runs with or without beam crossing angle

~ 4x108 shower events in Arm1+Arm2 ~ 106 π0 events in Arm1 and Arm2

Status Photon spectra at 900 GeV and 7 TeV, π0 spectra at 7TeV are

published Taking data at 4TeV/Z p-Pb collision NOW Upgrade to more rad-hard detectors for 14TeV in 2015 18

Observed event

Energy & PID

Position & multihit ID

Longitudinal development

Lateral development

Silicon X

Silicon Y

Particle Identification

20

(L90% indicates the depth of shower)

Photon event Hadron event

(Adriani et al., PLB, 2011)

+ ; dataHistograms; MC

90%

21

Photon spectra @ 7TeV (Data vs. Models)

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

Adriani et al., PLB, 703 (2011) 128-134Around 0 degree (On axis) Off axis

Photon spectra @ 900GeV

22

Adriani et al., PLB, 715 (2012) 298-303

small-η

= Large tower

big-η =Small tower

900GeV vs. 7TeV

Normalized by # of evnetsXF > 0.1 Statistical error only

XF spectra : 900GeV data vs. 7TeV data

Good agreement of XF spectrum shape between 900 GeV and 7 TeV.

Preliminary

Data 2010 at √s=900GeV(Normalized by the number of entries in XF > 0.1)Data 2010 at √s=7TeV (η>10.94)

LHCf coverage in XF-pT plane (XF = E/Ebeam)

900GeV vs. 7TeVwith the same PT region

900 GeV Small+large tower

23

π0 analysis • π0 candidate• 599GeV & 419GeV photons in 25mm

and 32mm tower, respectively• M = θ√(E1xE2)

24

Longitudinal development

Lateral development

Silicon X

Silicon Y

Small Cal.

LargeCal.

m 140= R

I.P.1θ

γ1(E1)

γ2(E2)

140mR

25

Adriani et al., PRD, 86, 092001 (2012)

π0 pT distribution in different rapidity (y) ranges

π0 <PT>

26<pT> comparison with UA7 at 630GeV (Pare et al., PLB, 242, 531 (1990))

ybeam - y

xF = E/E0

Playing a game with air shower (effect of forward meson spectra)

27

• 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

E=E1+E2

E1

E2

xF = E/E0

pT

An example of filtering

28

π0 spectrum

photon spectrum

DPMJET3+filter

2.5x1016 eV proton

~30g/cm2

Future

• Neutron spectra in 7TeV p-p … analysis on going• 4TeV/Z p-Pb … data taking on going• Joint analysis with ATLAS … data ready• 14 TeV p-p in 2015 … detector upgrade on going• Light nuclei at LHC, RHIC??? … possibility in discussion

29

Neutron Spectra at 7TeV pp(models)

30

Model predictions

Model predictions smeared by the LHCf energy resolution

31

p-Pb collisionsPhoton spectrum at the p remnant

Neutron spectrum at the p remnant(energy resolution taken into account)

• 1st collider experiment pA (dA done at RHIC)• LHCf triggers ATLAS to take common events with central

32

Leading baryons Multi meson production

What to be measured at accelerators?

proton / neutron

π0

π+

π-

γ

1. Inelastic cross section（ interaction mean free path）

3. Nuclear effect

elasticity (Ebaryon/E0)baryon spectrum

inelasticity (Emeson/E0= 1-elasticity)multiplicitymeson spectrum

2. Particle production

Note: √s=14TeV <=> Elab=1017eV

Summary

33

Experiments at LHC provide useful data to calibrate CR interaction models

LHCf is a dedicated experiment to measure forward particles effective to the air shower development

LHCf completed operation at 900GeV and 7TeV p-p collisions and published photon and π0 spectra

None of the models perfectly describe the LHCf results, but models well bracket the experiment (this is generally true for the other LHC results).

No sizable collision energy dependence is so far found Forward meson spectra is effective in <Xmax> LHCf is proceeding more analysis, takes more data with

p-Pb collisions and 14TeV p-p collisions, and more…

34

Cosmic-ray spectrum & Colliders

LHC

14T

eV

Teva

tron

LHC

0.9

TeV

LHC

7 Te

V

SppS

RHIC

ISR

1010 1020 eV

Knee: end of galactic proton CR

End of galactic CR and transition to extra-gal CR

Ankle (GZK) cutoff: end of CR spectrum

Perfect (or best at least) understanding up to 1017eV helps CR physics

Backup

35

LHCｆカロリーメータ構造n, gamma

• 全発光量からエネルギーを、形状から粒子を判定• <7TeVの入射粒子に対して、（特に電磁）シャワーは理解されている

37

38

Rapidity vs Forward energy spectra

η=8.40

η=8.77 η=8.40

η=8.77

η

∞8.7

θ[μrad]

0

310

Projected edge of beam pipe

Viewed from IP1(red:Arm1, blue:Arm2)