Neutral particles energy spectra for 900 GeV and 7 TeV p-p - - PowerPoint PPT Presentation

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Neutral particles energy spectra for 900 GeV and 7 TeV p-p - - PowerPoint PPT Presentation

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Neutral particles energy spectra for 900 GeV and 7 TeV p-p collisions, measured by the LHCf experiment Physics at LHC 2012, Vancouver (BC) Raffaello D'Alessandro* on behalf of the LHCf collaboration *Universit di Firenze &

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SLIDE 1

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 1

Neutral particles energy spectra for 900 GeV and 7 TeV p-p collisions, measured by the LHCf experiment

Raffaello D'Alessandro*

  • n behalf of the LHCf collaboration

*Università di Firenze & INFN-Firenze

Physics at LHC – 2012, Vancouver (BC)

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SLIDE 2

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 2

Outline

  • Introduction and physics case
  • The detector
  • Photon and π0 analysis
  • Status of LHCf and future prospects
  • Conclusions
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SLIDE 3

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 3

The physics case lies in cosmic ray energy spectrum and composition

  • AGASA and HiRes showed a marked discrepancy in results 10 years ago
  • Recent results Auger, HiRes (final), and TA indicate the presence of GZK cutoff
  • Absolute values differ between experiments and between detection methods used.
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SLIDE 4

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 4

Composition too …..

  • Xmax gives information of the

primary particle

  • Results are different between

experiments

  • Interpretation relies on the MC

prediction and has quite strong model dependence

Outer atmosphere limit

Xmax

Proton and nuclear showers

  • f same total energy

HiRes Auger

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SLIDE 5

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 5

LHCf : a bridge between cosmic ray physics and accelerators

  • Use the colliding beams at LHC

to study the interaction of UHE primary cosmic rays in the atmosphere.

  • ECM ~ ( 2 × Elab × Mp ) ½
  • √s =14TeV collision at LHC →

1017eV cosmic ray impacting on the atmosphere

  • 1. Inelastic cross section (ex. by TOTEM)
  • 2. Forward energy spectrum
  • 3. Inelasticity

large model dependence...

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SLIDE 6

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 6

Where colliders stand on the cosmic ray spectrum

SppS RHIC ISR LHC 0.9TeV LHC 14 TeV LHC 7 TeV

  • Pioneering measurements

performed by UA7 at the SppS collider at CERN in the 80s

(E. Pare et al., Phys. Lett, B242 (1990), 531.)

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SLIDE 7

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 7

Where does the energy flow ?

  • Most of the energy flows in the very forward direction
  • Particles with XF > 0.1 contribute to 50% of the air shower
  • Very important to study what's happening at high eta

8.4 < h <∞ All particles Neutral Multiplicity Energy Flux

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SLIDE 8

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 8

The LHCf experiment

  • Here the beam pipe splits in the two separate tubes that circle LHC
  • Charged particles (and the proton beams) are channelled away by the magnets
  • Unique configuration (better than SppS) that allows the LHCf calorimeters to

extend their coverage to |h|> 8

LHCf/ZDC

TAN

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SLIDE 9

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 9 INTERACTION POINT INTERACTION POINT IP1 (ATLAS ) IP1 (ATLAS )

De te c to r II De te c to r II Tung s te n Tung s te n S c intilla to r S c intilla to r S ilic

  • n

S ilic

  • n 

s trips s trips De te c to r I De te c to r I Tung s te n Tung s te n S c intilla to r S c intilla to r S c intilla ting f i be rs S c intilla ting f i be rs

44X0, 1.6 int

140 m 140 m n π0 γ γ 8 cm 6 cm Front Counter Front Counter

The LHCf detectors (1)

  • Two “tiny” E.M. calorimeters with precise reconstruction of

transverse and longitudinal shower profiles

Arm#2

Arm#1

90mm 2 9 m m

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SLIDE 10

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 10

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

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SLIDE 11

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 11

  • Measurement of zero degree single photon energy spectra for √ s = 7

TeV proton–proton collisions at LHC. (Physics Letters B 703 (August 2011) 128–134)

  • Measurement of zero degree inclusive photon energy spectra for √ s =

900GeV proton-proton collisions at LHC. (Submitted to Physics Letters B)

  • Analysis Procedure

– Energy Reconstruction from total energy deposition in a tower

(corrections for shower leakage, light yield etc.)

– Particle Identification by analysis of the longitudinal shower

development

– Remove multi-particle events by looking at transverse energy deposit – Two Pseudo-rapidity regions selections, η>10.94 and 8.81<η<8.9 – Combine spectra between the two detectors – Compare data with the expectations from the models

Inclusive photon spectrum analysis

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SLIDE 12

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 12

Energy and Particle ID

  • Impact position from lateral distribution
  • Position dependent corrections
  • Light collection non-uniformity
  • PID criteria based on transition curve
  • L90%

Arm1 Example L90 is the longitudinal distance in radiation lengths measured from the entrance to a calorimeter to the position where 90% of the total shower energy has been deposited

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SLIDE 13

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 13

Inclusive photon (continued)

  • Reject events with multi-peaks

– Identify peaks in one tower with position sensitive layers – Select only single peak events for spectra – Efficiency evaluated from MC and Data (artifical samples)

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SLIDE 14

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 14

Acceptance and Energy scale

  • R1 = 5mm, R2-1 = 35mm, R2-2 = 42mm, q = 20o
  • Small Tower → h > 10.94
  • Large Tower → 8.81 < h < 8.99
  • Energy scale checked by π0 identification from two separate tower events.
  • Mass shift observed both in Arm1 (+7.8%) and Arm2 (+3.7%)
  • No energy scaling applied, but shifts assigned in the energy scale systematic error

Arm2 Data Arm2 MC

Peak at 140.0 ± 0.1 MeV Peak at 135.0 ± 0.2 MeV

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SLIDE 15

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 15

Photon Spectra

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SLIDE 16

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 16

7TeV single photon comparisons.

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

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SLIDE 17

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 17

900 GeV results

  • Data sets used in the analysis were taken on 2, 3 and

27 May 2010 during the LHC operations with proton-proton collisions at √s =900 GeV, (Fill ID = 1068, 1069 and 1128)

  • Monte Carlo(MC) used the hadronic interaction

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

  • The detector response was calculated by using the

EPICS 8.81/COSMOS 7.49 simulation package .

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SLIDE 18

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 18

900 GeV single photon

Systematic uncertainties of the absolute energy scale were evaluated from the reconstructed invariant mass of 0s from the 7 TeV data. These differences were compatible with uncorrelated energy scale errors (±3.5 %) for the SPS beam calibrations or long term time variation. Energy scale uncertainties were estimated to be

[ 10.2%,+1.8%] and [ 6.6%,+2.2%] for Arm1 and Arm2.

Background levels were estimated as about 1 % and 2 % for the small and large towers, respectively, in both Arms. The estimated backgrounds were subtracted from the energy spectra. Because the f l ux of secondary particles produced by s=900GeV proton-proton collisions is expected to be uniform over the acceptance

  • f the LHCf detectors, the ‘beam center’ can not be determined

directly from our measurements. In this analysis, we assumed that the beam center was at the center position determined by the alignment measurement of the detectors. Systematic uncertainty caused by the uncertainty of the template f i tting method for obtaining the photon spectra.

  • Same type of selection as in the

previous case.

  • Lower energy photons
  • No p0 mass .
  • No reconstructed beam position.
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SLIDE 19

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 19

900 GeV, Data vs MC

  • Combined Arm1 and Arm2 photon energy spectra compared with

MC predictions. All systematics included except luminosity.

  • Similar behaviour to 7 TeV data.
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SLIDE 20

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 20

900 GeV comparisons continued …...

  • Ratio of MC spectra divided by data.

Comparison 7 TeV vs 900 GeV spectra

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SLIDE 21

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 21

LHCf 7TeV p0 analysis

  • Analysis finalised and paper submitted
  • PID with L90
  • Mass peak used for selection
  • More PT bins (2g in one tower)
  • PT spectra

Type-I Type-II

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SLIDE 22

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 22

LHCf 7TeV p0 spectra

Type-I sM=3.7% Type-II

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SLIDE 23

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 23

p0 spectra vs MC

  • EPOS shows the best agreement
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SLIDE 24

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 24

p0 spectra continued ….

  • Fit of the pT spectra,exponential

distribution with the form:

  • from which the average <pT> :
  • K is the modified Bessel function,

T from the fit is consistent with 100 MeV typical of soft QCD.

Averaged pT for the 6 y regions ylab y

beam y, where beam rapidity y beam is:

8.92 for s = 7TeV and 6.50 for s = 630GeV.

  • R. Hagedorn, Riv. Nuovo Cim. 6:10, 1 (1983)
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SLIDE 25

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 25

Proton Lead Run

  • Physics goals:

– model discrimination from a cosmic-ray point of view, by photons,

neutral pions & neutrons

– nuclear modification factor – inelasticity and others?

  • LHCf measurement for p-Pb interactions at 3.5TeV proton energy

could be easily and finely integrated in the LHCf global campaign.

Period Type Beam energy

LAB proton Energy (eV)

Detector 2009 p - p 450+450 GeV 4.3 1014 Arm1+Arm2 2009/2010 p - p 3.5+3.5 TeV 2.6 1016 Arm1+Arm2 2012 p – Pb 3.5 TeV proton E 1016 Arm2 2014 p - p 7+7 TeV 1017 Arm1+Arm2 upgraded

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SLIDE 26

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 26

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

  • Simulating protons with energy Ep = 3.5 TeV
  • “Arm2” geometry considered on both sides of IP1 to

study both p-remnant side and Pb-remnant side

  • Results are shown for DPMJET 3.0-5 and EPOS

1.99, 107 events each sNN = 4.4TeV

140 m 140 m

p-beam Pb-beam “Pb-remnant side” “p-remnant side”

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SLIDE 27

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 27

A word of caution

  • Results are shown for DPMJET 3.0-5 and EPOS 1.99

– EPOS 1.99 does not consider Fermi motion and Nuclear Fragmentation.

Problems for the Pb-remnant side results.

  • QGSJET2 can be used for p-Pb collisions. Works in

progress.

  • Public version of other models (Sybill, HIJING,

Pythia etc.) cannot be used for p-Pb collisions

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SLIDE 28

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 28

Proton-remnant side: multiplicity

n

  • Small tower

Big tower

n

Small tower

g

Big tower

multi-hit events are <~1% of single events

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SLIDE 29

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 29

Lead-remnant side - multiplicity

n

Small tower

g

Big tower

There might be too many neutrons => Use of Arm2 which has finer pitch Si -strip detectors First p-remnant side, then Pb-side by swapping beams

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SLIDE 30

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 30

Proton-remnant side: photon spectrum

Small tower Big tower

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SLIDE 31

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 31

Lead-remnant side: photon spectrum

Small tower Big tower

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SLIDE 32

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 32

Proton-remnant side:n spectrum and p0 spectrum

  • 35% Energy smearing

for hadrons

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SLIDE 33

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 33

g invariant cross section: p-remnant side

  • Enough statistics for a clean

determination of the Xsec

  • With the g (p0)spectrum in 4.4

TeV pp collisions, we can extend the measurement of the nuclear modification factor to higher energies and to h >8.4

  • A big suppression has been

reported for h=4

NMF by STAR@RHIC (PRL97, 152302, 2006)

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SLIDE 34

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 34

Conclusions

  • Thanks to the Conference Committee for the splendid conference

and the opportunity given to present these results.

  • LHCf photon and p0 analysis has been completed

–

Many detailed systematic checks

–

First comparison of various hadronic interaction models with experimental data in the most challenging phase space region (8.81 < h < 8.99, h > 10.94)

–

Large discrepancy especially in the high energy region with all models

–

Implications on UHECR Physics under study in strict connection with relevant theoreticians and model developers

  • Other analyses are in progress (hadrons, PT distributions, ….)
  • LHCf was removed from the tunnel on July 20, 2010
  • We will come back in the TAN for the p-Pb run in 2012
  • We are upgrading the detectors to improve their radiation hardness (GSO

scintillators and rearrangement of the silicon layers)

  • We will anyway come back in LHC for the 14 TeV run with upgraded detector.
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SLIDE 35

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 35

Backup: Xsec measurement

  • sinel result @ 7TeV

TOTEM 73.5+-0.6+1.8-1.3 mb ds/dt(t=0) ATLAS 69.4+-2.4+-6,9 mb MBTS sample CMS 68.0+-2.0+-2.4+-4 mb Ntrk sample ALICE 72.7+-1.1+-5.1 mb VZERO sample

Tevatron UA4 ISR LHC

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SLIDE 36

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 36

Backup: LHCf PT range

pp 7TeV, EPOS

g p

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SLIDE 37

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 37

Backup: Hadrons

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SLIDE 38

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 38

Backup: Inelasticity~ 0o neutron spectra

  • Important for Xmax and also N
  • Measurement of inelasticity at LHC energy

Neutral hadrons at 14 TeV (LHCf acceptance, no resolution) Neutral hadrons at 14 TeV (LHCf acceptance, 30% resolution) Inelasticity k= 1-plead/pbeam

If large k rapid development If small k deep penetrating

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SLIDE 39

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 39

Backup: The LHCf detectors (2)

Performances Energy resolution (> 100 GeV): < 3% for 1 TeV g &  30% for n Position resolution for photons:  40 μm (Arm2)

Sampling and imaging EM calorimeter

§ Absorber: W (44 r.l, 1.55λI ) § Energy measurement: plastic scintillator tiles § 4 tracking layers for imaging:

XY-SciFi (Arm1) and XY-Silicon strip(Arm2)

§ Each detector has two calorimeter towers,

which allow to reconstruct π0

Front Counters

  • thin scintillators 80x80 mm
  • monitors beam condition
  • Van der Meer scan

25mm 32mm

Arm2 Arm1

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SLIDE 40

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 40

Backup: Upgrade (1)

  • GSO (Gadolinium oxyorthosilicate) properties

– (EJ260: plastic scintillator used in the current LHCf detectors)

GSO EJ-260 density(g/cm3) 6.71 1.023 r.l.(cm) 1.38 14.2 decay time(ns) 30-60 9.6 Fluorescence(NaI=100) 20 19.6 λem(nm) 430 490 Refractive(@λem) 1.85 1.58 tolerance(Gy) 106 100 melting point(℃) 1950 ー

Fast among inorganic scintillators Best amongst known scintillators Similar to the current scintillators Heavy; reason to reduce 3->1mm Light collection may differ

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SLIDE 41

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 41

Backup: Upgrade (2)

  • Uniformity test using C beam at HIMAC

– (preliminary results from quick analysis)

PMT via fiber bundle PMT via fiber bundle No particle due to the beam pipe mm mm mm mm

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SLIDE 42

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 42

Backup: Upgrade (3)

GSO bar bundle and quartz fiber light guide GSO plate and light guide packed in a new holder GSO plates and bars as calorimeters, but without Tungsten absorber layers

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SLIDE 43

Physics at LHC – 2012 Vancouver, BC

  • R. D'Alessandro

Università di Firenze & INFN-Firenze 43

Backup: re-installation in TAN

  • Careful planning …....

LTEX Meeting - May 10th, 2012

Operation Time (min) Required Personnel Position Individual Dose (µ Sv) Collective Dose (µ Sv)

9

Placement (no fine positioning)

15

2 physicists from LHCf On top of the TAN

20 40 10

Installation of the Front Counter

10

2 physicists from LHCf On top of the TAN and behind it on the footbridge

13 26 11

Cabling for preamp and FC

5

2 physicists from LHCf On top of the TAN and behind it on the footbridge

7 14 12

Additional cabling for the electronics box

10

2 physicists from LHCf On top and side of the TAN

13 26 13

Survey

4 h

2 technicians from BE/ABP Around the TAN region

? ? 14

Electronics commissioning

(8 h) 60

2 physicists from LHCf This test is performed from

  • USA15. In case of problems 2

physicists from LHCf will have to work on top of the TAN for a period which depends on the kind of problem (typically 15-60 min)

80 160 15

Mechanical commissioning (manipulator)

(8 h) 30

2 physicists from LHCf Test performed mainly from

  • USA15. One physicist is

required to stay on top of the TAN for 30 minutes maximum

40 40 16

Bring back detector shielding boxes

10

1 physicists from LHCf TAN->PM15

1 1 17

Exit the zone

10

2 physicists from LHCf TAN->PM15

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SLIDE 44

TAN- LSS1R

17 µSv/h (dessous) 10.5 µSv/h (dessus) 4.7 µSv/h 4.8 µSv/h 5.6 µSv/h 5 µSv/h 24.5 µSv/h (milieu côté tunnel) 6 µSv/h 4 µSv/h (*) 20 µSv/h (*) 4.2 µSv/h

Survey réalisé le 25/04/12 à 14h00

RP measurements done on April 25th 2012 – 14h All values at contact

Thanks to: A. Herve (CERN DGS/RP)

44 LTEX Meeting - May 10th, 2012