Latest results from LHCf on very forward particle production at LHC

+

Latest results from LHCf on very forward particle

production at LHC

Oscar AdrianiUniversity of Florence & INFN Firenze

Latest results from the LHCCERN, July 12th, 2012

+Physics MotivationsImpact on High Energy Cosmic Ray Physics

O. Adriani Latest results from LHCf Cern, July 12, 2012

+ The Cosmic Rays energy spectrum

1 particle/m2/sec

1 particle/m2/year

1 particle/km2/year

1 particle/km2/century

Direct Measurement by Balloon and Satellite

Air shower technique

+


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

Altit

ude

[km

]Radius [km]

γ p Fe


+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

+ The Chemical composition can be inferred from

the depth of the maximum of the shower (Xmax)

Example II: Chemical Composition

Shower depth [g/cm2]

Proton

IronGamma-ray

Xmax

E=1019eV BUT…. The results depend on the precise knowledge of the hadronic interaction mechanism!!!!!

6

PROTON

IRON

TA

Auger


Model uncertainty

+ The Chemical composition can be inferred from

the depth of the maximum of the shower (Xmax)

Example II: Chemical Composition

Shower depth [g/cm2]

Proton

IronGamma-ray

Xmax

E=1019eV BUT…. The results depend on the precise knowledge of the hadronic interaction mechanism!!!!!

7

PROTON

IRON

TA

Auger


Model uncertainty

Both in the energy determination and X max

prediction MC sim

ulations are used, and are one

of the greater sources of uncertainty.

Experimental tests of hadron interactio

n models

are necessary! LHCf

+

Why LHCf @ LHC?The experimental set-up


+The Cosmic Ray spectrum

0.9TeV

7TeV

14TeV

Direct Indirect

LHC Energy range is very interesting for Cosmic Ray Physics!


+ Air Shower development Total cross section

o Large σ rapid developmento Small σ deep penetrating

Multiplicity (N)o Large N rapid development

large number of muonso Small N deep penetrating

small number of muons

Inelasticity(k)/Secondary spectrao Large k, Softer spectra

rapid developmento Small k, harder spectra

deep penetrating


+ LHC experiments Whole pseudo-rapidity is covered by the different LHC experiments

R. Orava, (2005)

Key parameters for air shower developments Total cross section

↔ TOTEM, ATLAS, CMS Multiplicity

↔ Central detectors Inelasticity/Secondary spectra

↔ Forward calorimeters LHCf, ZDCs

+


LHCf: location and detector layout

44 X0, 1.6 lint

INTERACTION POINT

IP1 (ATLAS)

Detector IITungsten

ScintillatorSilicon

mstrips

Detector ITungsten

ScintillatorScintillating

fibers140 m 140 m

n π0

γ

γ8 cm 6 cm

Front Counter Front Counter

Arm#1 Detector20mmx20mm+40mmx40mm4 X-Y SciFi tracking layers

Arm#2 Detector25mmx25mm+32mmx32mm4 X-Y Silicon strip layers

Expected Performance Energy resolution < 5% for g~30% for neutronsPosition resolution ~ 100μm

+What LHCf can measure?


Multiplicity@14TeV Energy Flux @14TeV

Low multiplicity !! High energy flux !!

simulated by DPMJET3

Energy spectra and Transverse momentum distribution of photons, neutrons and p0 in the pseudorapidity region h > 8.4

+What LHCf can measure?


Multiplicity@14TeV Energy Flux @14TeV

Low multiplicity !! High energy flux !!

simulated by DPMJET3

Energy spectra and Transverse momentum distribution of photons, neutrons and p0 in the pseudorapidity region > 8.4

The experimental challenge:

Very precisely measure the highest e

nergy LHC

photons (up to 7 TeV) with the sm

allest LHC

detector (~few cm2 )

+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 PLBCERN-PH-EP-2012-048“Measurement of forward neutral pion transverse momentum spectra for √s = 7TeV proton-proton collisions at LHC“Submitted to PRDCERN-PH-EP-2012-145

+


Inclusive g spectrum at 900 GeV

DPMJET 3.04

SIBYLL 2.1

EPOS 1.99

PYTHIA 8.145

QGSJET II-03

Gray hatch : Systematic Errors

Dat

aM

C/D

ata

+


Inclusive g spectrum at 7 TeV Gray

hatch : Systematic Errors

Magenta hatch: MC Statistical errors

Dat

aM

C/D

ata

+


Inclusive g spectrum at 7 TeV Gray

hatch : Systematic Errors

Magenta hatch: MC Statistical errors

Dat

aM

C/D

ata

None of the Models a

grees with the

data!

These measurement are important to

improve the hadronic interaction

models in the high energy region

+


small-η

= Large tower

big-η =Small tower

Coverage of the photon spectra in the plane Feynman-X vs PT

Comparison between 900 GeV and 7 TeV spectra

+


small-η

= Large tower

big-η =Small tower


900GeV vs. 7TeVwith the same PT region

900 GeV Small+large tower


+


small-η

= Large tower

big-η =Small tower

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)


900GeV vs. 7TeVwith the same PT region

900 GeV Small+large tower


+


7 TeV p0 analysis

m 140= R

I.P.1

g1(E1)

g2(E2)

140m

R

Mass, energy and transverse momentum are reconstructed from the energies and impact positions of photon pairs measured by each calorimeter

+


p0 Data vs MC: PT spectra for different rapidity bins

+


p0 Data vs MC dpmjet 3.04 & pythia 8.145

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.


+ p0 analysis at √s=7 TeV

• 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

PLB 242 531 (1990)

ylab = ybeam - y

Submitted to PRD (arXiv:1205.4578).

pT spectra vs best-fit function Average pT vs ylab

YBeam=6.5 for SPSYBeam=8.92 for7 TeV LHC

<PT> for different y

bins

+What’s next and … conclusions …



+LHCf Future PLANS: Ion run and 14 TeV

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

g

p –remnant side

Re-in

stal

lJul

7TeV2010 2013 2014

LHCf I

14TeV

LHCf II

Detector upgrade

LHC2011/2012

shutdown

Re-

inst

all

LHCf-HI


+ 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

+Backup slides


+

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 3.0-5 and EPOS 1.99, 107 events each

140 m 140 m

p-beam

Pb-beam

“Pb-remnant side”

“p-remnant side”

nTeV/nucleo 38.1 pN EAZ

E

What LHCf can measure in the p+Pb run E, pT, h spectra of neutral particles

+


Proton remnant side – Photon spectra

+


Proton remnant side - Neutron spectra

+Lead-remnant side – multiplicityPlease remind that EPOS does not consider Fermi motion and Nuclear Fragmentation

n

g

Small tower 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 <h>=4.

LHCf can extend the measurement at higher energy and for h>8.4Very important for CR Physics

Phys. Rev. Lett. 97 (2006) 152302

+Muon excess at Pierre Auger Obs.

Pierre Auger Collaboration, ICRC 2011 (arXiv:1107.4804)

Pierog and Werner, PRL 101 (2008) 171101

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 MCEPOS predicts more muon due to larger baryon production => importance of baryon measurement


+


Neutron at LHCf phase-space

By Tanguy Pierog, Modelists waiting for LHCf!!

+


Arm1 vs Arm2 comparison


+ π0 spectrum and air showers

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

π0 spectrum at Elab = 1017eV

DPMJET3 originalArtificial modification

Longitudinal AS development

Vertical Depth (g/cm2)

<Xmax>=718 g/cm2

<Xmax>=689 g/cm2

AUGER, ICRC 2011

+ LHCf operations @900 GeV & 7 TeV With Stable Beam at 900 GeV Dec 6th – Dec 15th 2009With 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 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

Shower Gamma Hadron

Arm1 46,800 4,100 11,527Arm2 66,700 6,158 26,094


+ p0 reconstruction

Reconstructed mass @ Arm2

measured energy spectrum @ Arm2

preliminary

An example of p0 events

• 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.

25mm 32mm

Silicon strip-X view

m 140= R

I.P.1

g1(E1)

g2(E2)

140m

R


+h Mass Arm2 detector, all runs with zero crossing angleTrue h Mass: 547.9 MeVMC Reconstructed h Mass peak: 548.5 ± 1.0 MeVData Reconstructed h Mass peak: 562.2 ± 1.8 MeV (2.6% shift)

+Type-I Type-II

Type-II at small tower

Type-II at large tower

Type-ILHCf-Arm1

Type-IILHCf-Arm1

LHCf-Arm1Data 2010

BG

Signal

Preliminary

•Large angle•Simple•Clean•High-stat.

•Small angle•large BG•Low-stat., but can cover•High-E•Large-PT

π0 analysis at √s=7TeVSubmitted to PRD (arXiv:1205.4578).


Documents

Latest results from LHCf on very forward particle production at LHC