the first results of the lhcf experiment and...

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Y.Itow, The first results of the LHCf experiment and future LHCf Catania@ 6 Jul 2011

The First Results of the LHCf experimentand future

Yoshitaka ItowSolar-Terrestrial Environment

LaboratoryNagoya University

for the LHCf collaboration

Catania Mini-WSJul 6, 2011, U.of Catania

Y.Itow, The first results of the the LHCf experiment and future LHCf Catania@ 6 Jul 2011

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Menu

Introduction to the LHCf experiment1st results from 7TeV collisionsOn-going activityLong term planDiscussion

Impact on air shower developmentImpact on very forward interaction


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① Inelastic cross section

② Forward energy spectrum

If large krapid development

If small k deep penetrating

If large σrapid development

If small σdeep penetrating④ 2ndary interactions

③ Inelasticity k

If softershallow development

If harderdeep penetrating


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K.Fukatsu, Y.Itow, K.Kawade, T.Mase, K.Masuda, Y.Matsubara, G.Mitsuka, K.Noda, T.Sako, K.Suzuki, K.Taki

Solar-Terrestrial Environment Laboratory, Nagoya University, JapanK.Yoshida Shibaura Institute of Technology, JapanK.Kasahara, M.Nakai, Y.Shimizu, T.Suzuki, S.Torii

Waseda University, JapanT.Tamura Kanagawa University, JapanY.Muraki Konan University, JapanM.Haguenauer Ecole Polytechnique, FranceW.C.Turner LBNL, Berkeley, USAO.Adriani, L.Bonechi, M.Bongi, R.D’Alessandro, M.Grandi, H.Menjo, 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, SpainD.Macina, A-L.Perrot CERN, Switzerland

The LHCf Collaboration


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140 m 140 m

n π0

γ

γ

8 cm 6 cm

The LHCf experimentNeutral particle measurement at 0 degree of LHC IP1

IP1 (ATLAS)IP1 (ATLAS)

ArmArm 22Arm 1Arm 1 Front Counter Front Counter

ATLAS

140m

140m

ＬＨＣf (Arm1)

ＬＨＣf (Arm2)

44X0, 1.6 λint

20mmx20mm+40mmx40mm4 SciFi tracking layers

25mmx25mm+32mmx32mm4 Silicon strip tracking layers

44X0, 1.6 λint


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LHCf calorimeters

Arm#2 DetectorArm#1 Detector 90mm290mm


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Setup in IP1-TAN (side view)

LHCf Front Counter

LHCfCalorimeter

BRAN-IC

ZDC type1

IP1

ZDC type2

Beam pipe

TAN Neutral particles

Side view

BRAN-Sci


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LHCf detector characteristicsSingle incident per tower with the small aperture as possible (comparable to tungsten Moliere radius)Shower leakage can be corrected by shower incident position.A pair of tower for π0 reconstructionMovable to cover PT gapCovered |η| > 8.4

Gamma-rays (E>100GeV,dE/E<5%)Neutral Hadrons (E>a few 100 GeV,

dE/E~30%)Neutral Pions (E>700GeV, dE/E<3%)

Shower incident position (170µm / 40µm for Arm1/Arm2

σ=40μmfor 200GeVelectrons

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Y.Itow, The first results of the LHCf experiment and future LHCf Catania@ 6 Jul 2011Calorimeter acceptance (viewed from IP)

θ[μrad]

0

310

0 crossing angle

100urad crossing angle

Projected edge of beam pipe

beam1 beam2

Neutral fluxcenter

Neutral flux

center

crossing angle


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Forward E spectra by LHCf @ 14TeV (MC for ~0.1nb-1)

π0

single γ

Neutrons (w/ 30% resolution)

Neutrons (true energy)


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Brief history of LHCfMay 2004 LOI

Feb 2006 TDR

June 2006 LHCC approved

Jan 2008 Installation

Aug 2007SPS beam test

Sep 20081st LHC beam

Jul 2006construction

Mar 20101st 7TeV run

Dec 20091st 900GeV run Jul 2010

Detector removal


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2009-2010 run summary (7TeV)

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107

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Integrated showers at 7TeV

# of

sho

wer

s

Dete

ctor

rem

oved

High luminosity (L=3~20e29cm2s-1)(1e11ppb, b*=3.5m,Nb=1~8)100µrad crossing

Arm1 π0 stat.

Low luminosity (L=2~10e28cm2s-1)(1~2.5e10ppb, β∗=2m,Nb=1~4) No crossing angle

500K

1000K

# of

π0

900GeV

4/1 5/27 7/22

4/4 5/30 7/25


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The first paper

• Limited Data :o 15 May 2010 17:45‐21:23, Low Luminosity 6x1028o 0.68 nb‐1 for Arm1, 0.53nb‐1 for Arm2

• “Single” γ energy spectra for two Psudo-rapidity bins,o eta > 10.94, 8.81 < eta < 8.99

" Measurement of zero degree single photon energyspectra for√s = 7 TeV proton-proton collisions at LHC “

(submitted to PLB, arXiv:1104.5294, CERN-PH-EP-2011-061 )Video available for seminar by Sako at CERN

http://indico.cern.ch/conferenceDisplay.py?confId=137111


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Typical event display (7TeV π0 )TeV π0 !


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Energy reconstructionEphoton = f(Σ(dEi)) (i=2,3,…,13)

( dEi = AQi determined at SPS. f() determined by MC. E : EM equivalent energy)Shower incident positions by position sensitive layers.Position dependence corrections– Light collection non-uniformity– Shower leakage-out / leakage-in

– Energy scale – Calibrated with SPS 150-250 GeV e- beam– Check with π0 mass peak in 7TeV data

( Arm1 (+7.8%) , Arm2 (+3.7%) )

15pi0mass (arm1) pi0mass (arm2)


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Multi-incident rejection Single shower event selection– Reject two shower hits in a tower by a lateral shape

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Arm1 Small

Dou

ble hit d

etection

efficiency

Arm2 small

0 1 2 3 (TeV) 0 1 2 3 (TeV)


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PID ( γ / hadron separation)PID ( γ-like shower selection)– Select γ-like events in L90% distribution and correct ε

(efficiency) and P (purity)

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γ had

Definition of L90%

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Select rapidity regions

Consistency check btw Arm1 and Arm2

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Arm1+Arm2 combined spectra

Normalized by number of inelastic pp collisions with assumption as total inelastic cross section of 71.5mb

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Comparison with Models

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

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Spectral deformation bias• Suppression due to multi-hit cut at medium energy• Overestimate due to multi-hit detection inefficiency

at high energy (mis-identify multi photons as single)• No correction applied, but same bias included in MC

to be compared

TRUEMEASURED

TRU

E/M

EASU

RED

True: photon energy spectrum at the entrance of calorimeter


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Systematic errors

Spectrum shapeE-scale Multi-shower rejection efficiency PID efficiency / purity subtractionNeutral flux center

Absolute Lumi measurement by FC (calibrated by VdM-scan)Normalized by number of inelastic pp collisions

with assumption as total inelastic cross section of 71.5mb


23syst

emat

ic e

rror

s on

sha

pe

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On-going analyses

7TeV data900GeV data


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2009-2010 900GeV analysis

900 GeV run (no crossing angle)06 Dec. –15 Dec. 2009 (27.7 hrs, 500K collisions)

2.8K / 3.7K single showers at Arm1 / Arm202 May – 27 May in 2010 (15hrs, 5.5M collisions)

44K / 63K single showers at Arm1 / Arm2

• Because LHCf can cover only small PT region at < 450GeV, PT distribution will not be provided.

• No possibility of detection of pi0, eta and etc


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Particle ID

L90% @ 40mm cal. of Arm1

MC (QGSJET2)Data

Prelim

inary

Thick for E.M. interaction (44X0) Thin for hadronic interaction(1.7λ)

A transition curve for Gamma-ray A transition curve for Hadron

Definition of L90%

Gamma-ray like

• ~ 90% efficiency with ~10% contamination

Hadron like


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900GeV spectra Eff. uncorrected, stat.error onlyNormalized by total # of events.

GammaGamma--ray likeray like Hadron likeHadron like

GammaGamma--ray likeray like Hadron likeHadron like

Arm

1A

rm1

Arm

2A

rm2

Prelim

inary

Prelim

inary


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On-going work for 7TeV dataFor Photons (>100GeV)

Energy spectrum in wider rapidity rangePT distribution as a function of photon energy

For Hadrons (> some hundreds GeV)Energy Spectrum and PT distribution with less precision.Energy resolution for hadrons is about 30%.

For Pi0's (>500GeV)Energy spectrum and PT distribution.

For Eta, K0S and Lambda

Maybe only some information can be provided, like production ratio of Eta/Pi0.

With double side coincidence,With Central information from ATLAS


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PT distribution for photonspp 7TeV, EPOS

1TeV<Eg<1.1TeV


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7TeV study: Reconstruction of η

π0 Candidate

η Candidate

Prelim

inary

Another good energy calibration point.Production yield of η much differs among the models.


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LHCf future run plan

Jul

7TeV

2010 2013 2014

LHCf I

14TeV

LHCf II

Detector upgrade

LHC2011/2012

shutdown

Re-

inst

all

102010171014 eV

14TeV7 100.9TeV

KneeGZK

Ankle

AUGER, TATALE

2nd Knee?

Re-

inst

all?

LHCf-HI Replace with rad-hardGSO scintillator


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Foreseen “corrected” π0 spectrum at 14TeV (MC)

Uncertainty of Multi Hit contamination Uncertainty of energy scale ： assumed as ±5%Uncertainty of relative normalization btw 2 pos. <0.1%Uncertainty of neutral beam center <0.1％

Peak=134MeVσ=4.9MeV

Cut 125MeV- 145MeV

Based on ~104 π0 samples at 2 positions Mass cut

π0 energy resolution

H.Mejo,Astropart.Phys. 34 (2011) 513-520


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Coverage at 7TeV and 14TeV

All γ from IP

N

L

7TeV collisions

7 TeV 14 TeV

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Y.Itow, The first results of the LHCf experiment and future LHCf Catania@ 6 Jul 2011Measurement at several collisions energy

7 TeV10 TeV14 TeV (1017eV@lab.)

SIBYLL

7 TeV10 TeV14 TeV

QGSJET2

Secondary gamma-ray spectra in p-p collisions at different collision energies (normalized to the maximum energy)

SIBYLL predicts perfect scaling while QGSJET2 predicts softening at higher energy

Qualitatively consistent with Xmax prediction

Note: LHCf detector taken into account (biased)


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LHCf-HI ?p-Pb relevant to CR physics?CR-Air interaction is not p-p, but A1-A2 (A1:p, He,…,Fe, A2:N,O)

LHC Nitrogen‐Nitrogen collisionsTop: energy flow at 140m from IPLeft : photon energy spectra at 0 degree

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TotalNeutronPhoton


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Discussion

Impact on air shower development

Impact on very forward interaction


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π0 spectrum and air shower

Artificial modification of meson spectra and its effect to air showerImportance of E/E0>0.1 mesonsIs this modification reasonable?

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π0 spectrum at Elab = 1019eV

QGSJET II originalArtificial modification

Longitudinal AS development

Ignoring X>0.1 meson

X=E/E0

30g/cm2


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Very forward – connection to low-x physics

Very forward region : collision of a low-x parton with a large-x partonGluon become dominating in higher energy collision by self interaction.But they may be saturated (gluon satruration)

Increasing E

Low-x high-x

But LHCf sees much lower PT, soft interactions

soft hard semi-hard


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SummaryLHCf : Dedicated measurements of neutral particles at 0 deg at LHC energy for the verification of cosmic rays interaction models at 1017eV.Phase-I run successfully completed. Analysis on-going.

900 GeV run : ~ 100K showers in both arms7 TeV runs : ~300M showers, ~1M π0 in both armsDetector worked as designed. We can say something about model discrimination soon.

Revisit LHC for next energy upgrade at ~2014 with a rad-hard detector. Possible future Light Ion runs? R&D in progress.

UHECR data may hint ultra high energy interactions at beyond-LHC energy. To approach, LHCf will give firm base of understanding at 1017eV.


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Backup

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P-Pb collisionsWe are starting studies of measurement at p-Pb collisions with LHCf detectors.


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Contribution from very forward production5×1019 eV proton showers( 60 deg zenith)

# of

ele

ctro

ns

No cut

low XF γ origin ( xF < 0.05 )

π,Κ origin ( xF < 0.1 )

Half of shower particles comes from large XF γ

Measurement at very forward region Is needed


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Next stepRevisit LHC when next energy upgrade (i.e. @14 TeV in 2013).

Detector will be upgraded with rad-hard GCO scintillatorLight ion collisions to understand nuclear effects.

So far only heavy ions (Pb-Pb) collisions are forseen( in late 2010) at LHC, in which too much multiplicity for LHCf .Feasible study under going to cope with high multiplicity at 0 degree for light ions

0.5 particle/cm^23.5TeV/n N- N collisionsMulitiplicity in 0-1cm cone at 140m

DPMJET3QGSJET2


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Energy reconstructionEphoton = f(Σ(dEi)) (i=2,3,…,13)

( dEi = AQi determined at SPS. f() determined by MC. E : EM equivalent energy)Shower incident positions by position sensitive layers.Position dependent corrections– Light collection non-uniformity– Shower leakage-out– Shower leakage-in (in case of two calorimeter event)

44Light collection nonuniformity Shower leakage‐out Shower leakage‐in


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Multi-incident rejection Single event selection– Single-hit detection efficiency– Multi-hit identification efficiency (using superimposed

single photon-like events)– Effect of multi-hit ‘cut’ (next slide)

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Double hit in a single calorimeter

Single hit detection efficiency

Small tower Large tower

Double hit detection efficiency

Arm1

Arm2


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Uncertainty in Step.2Fraction of multi-hit and Δεmulti, data-MC

Effect of multi-hit ‘cut’ : difference between Arm1 and Arm2

46Single / (single+multi), Arm1 vs Arm2Effect ofΔεmulti to single photon spectra


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Uncertainty in Step.3Imperfection in L90%distribution

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Template fitting A

Template fitting B

(Small tower, single & gamma‐like)

Artificial modification in peak position (<0.7 r.l.) and width (<20%)

Original method

ε/P from two methods

(ε/P)B/ (ε/P)A


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Analysis Step.4π0 identification from two tower events to check absolute energyMass shift observed both in Arm1 (+7.8%) and Arm2 (+3.7%)No energy scaling applied, but assigned the shifts in the systematic error in energy

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m 140=R

θ

I.P.1θ

γ1(E1)

γ2(E2)

140mR

Arm2 Measurement

Arm2 MC

M = θ√(E1xE2)


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Beam Related Effects

Pile-up (7% pileup at collision)Beam-gas BGBeam pipe BGBeam position (next slide)

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MC w/ pileup vs w/o pileup

Crossing vs non‐crossing bunches Direct vs beam‐pipe photons


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Where is zero degree?

50Effect of 1mm shift in the final spectrum

Beam center LHCf vs BPMSW

LHCf online hit‐map monitor


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Luminosity EstimationLuminosity for the analysis is calculated from Front Counter rates:

The conversion factor CF is estimated from luminosity measured during Van der Meer scan

LVDM = nb f revI1I2

2πσ xσ yVDM scan

BCNWG paperhttps://lpc‐afs.web.cern.ch/lpc‐afs/tmp/note1_v4_lines.pdf

L = CF × RFC

Beam sizes σx and σy measured directly by LHCf

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Y.Itow, The first results of the LHCf experiment and future LHCf Catania@ 6 Jul 2011Geometrical Efficiency for Pi0, Eta

Pi0

Eta


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First Events at 900GeV collisions

Arm1(SciFi)

Longitudinal development

Lateral (X)Distribution

Lateral (Y)Distribution

Small tower Large tower

SCFI-X

SCFI-Y

Scinti.Layers

the first results of the lhcf experiment and...

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