Study of neutral baryon production at the very forward region of the - PowerPoint PPT Presentation

Study of neutral baryon production at the very forward region of the LHC Kentaro Kawade STE laboratory, Nagoya University, Japan 2 July 2013 @ Rio de Janeiro, Brazil

Contents • Introduction • Motivation • LHCf experiment • Detector performance • Data analysis • Summary

Hadronic interaction in cosmic-ray showers interaction models neutral baryons π 0 →2γ(EM) = LHCf → measurement of forward particles by using “accelerator” (EM shower) (Shower core) the cosmic-ray shower quite important to understand (neutron~94%, Λ ~6% (DPM3)) UHECR • Forward particle production is EM shower • Forward baryons leading baryon • Mesons μ +/- (Meson) (shower core) • Verifying the hadronic LHCf detector

The LHCf experiment of sampling and imaging strip sensor position sensor; SciFi or Silicon • scintillator Calorimeter; Tungsten & • calorimeters The LHCf detectors are composed • side of the LHC IP1 and “Arm2” are installed in both Two independent detectors “Arm1” • emitted to forward region of LHC LHCf measures neutral particles • LHC Interaction point 1 140m ● 140m Large tower 8.77< η <9.46 80 Vertical(mm) 70 60 50 44mm, 40 η 155~310µrad =8.77 30 22mm, Arm1 Detector 20 11mm, η =9.46 10 η =10.15 Small tower More details about LHCf 0~80µrad 0 η > 10.15 → 4 july Menjo’s talk () -10 Arm1 -20 -40 -30 -20 -10 0 10 20 30 40 Holizontal(mm)

Motivations; Forward baryons Muon excess in CR • Expected neutron energy spectra is important Forward baryon production • ( +30% than MC) observation is found relative to the MC predictions • • Very large difference in neutral Muon excess models is expected baryon spectra among the Direct measurement of inelasticity • 10000 4000 PYTHIA PYTHIA 9000 3500 EPOS EPOS QGSJET2 QGSJET2 8000 DPMJET3 DPMJET3 3000 SYBILL SYBILL 7000 2500 6000 Entries Entries 5000 2000 4000 1500 3000 1000 2000 500 1000 0 0 0 1000 2000 3000 4000 5000 6000 0 1000 2000 3000 4000 5000 6000 Energy[GeV] Energy[GeV] LHCf Small tower LHCf Large tower Proton Sim Iron Sim Data 10 2 S [VEM] 10 1 [T. Pierog, K. Werner PRL 101 , 10 0 500 1000 1500 2000 171101 (2008)] Radius [m] [ J.Allen, et al. ICRC2011 Proceedings]

Analysis

Detector performance LHCf detector was studied using MC simulations checked comparing with the beam experiment at SPS (350GeV proton) Small Large • The performance of the Detection ~70% ~70% efficiency • Detection efficiency Non ±1% ±4% linearity • Energy reconstruction Energy resolution 37~42% 36~48% • Position determination • The energy scale was Position 2.5~0.5 4.0~1.0 resolution mm mm (Details are summarized in my proceedings) icrc2013 #0850

Data statistic • MC • Data • Taken in May 2010 with √s = 7TeV (≒2.5x10 16 eV @ E Lab ) • Integrated luminosity 0.68nb -1 (calculated in previous study) • N inel = 0.68nb -1 * 71.5 [mb] ≒ 4.8 x 10 7 [collisions] (50M col) • QGSJET2 : 1x10 7 collisions • EPOS : 1x10 7 collisions • PYTHIA : 0.8x10 7 collisions • SYBILL : 0.5*10 7 collisions

Analysis method applied was used for the experimental data and MC calibrated by using SPS beams (for photon analysis) detection efficiency) was Input dE in calorimeter, SciFi • Same analysis procedure 3 fold coincidence in Event selection calorimeter Reconstruct hit position and shower shape (L 20% and L 90% ) • Calorimeter was well Reconstruct energy (1st) • No correction (PID, PID (energy, L 20% , L 90% ) Reconstruct energy and pT

Particle identification (PID) L 90% Shower development in a calorimeter Sample) L 20% efficiently and less contamination is essential L 90% are used for PID in this study containing 20% (90%) of total deposited energy obtained as below • To perform PID with higher hTC_Small_tower 8000 7000 6000 5000 4000 3000 • 2D method using L 20% and 2000 1000 0 0 5 10 15 20 25 30 35 40 Layer[r.l.] projection along the sloped line • L 20% (L 90% ) is the depth signal L90 - 0.25*L20 L 90% L90[r.l.] 1400 40 1200 35 30 1000 25 800 • 2D cut parameter L 2D is 20 600 hadron 15 400 photon 10 200 5 L 2D = L 90% - 1/4*L 20% 0 0 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 L 2D L20[r.l] L90 - 0.25*L20 L 20%

Preliminary result No rapidity selection No rapidity selection Small tower hData No efficiency correction No efficiency correction -6 -6 10 10 × × Only statistical error Only statistical error 4 /GeV /GeV 3.5 Data Data 3.5 inel inel events/N EPOS events/N EPOS 3 3 QGSJET2 QGSJET2 2.5 PYTHIA PYTHIA 2.5 LHCf Preliminary SYBILL SYBILL 2 2 LHCf Preliminary 1.5 1.5 1 1 0.5 0.5 0 0 0 1000 2000 3000 4000 5000 6000 7000 8000 0 1000 2000 3000 4000 5000 6000 7000 8000 Reconstructed Energy [GeV] Reconstructed Energy [GeV] LHCf Small tower LHCf Large tower • No model can explain our result perfectly

Next steps

The systematic errors • The major parts are listed in the table • Studies are ongoing % Luminosity +-5% PID +-10% Multi-hit event study ongoing Beam center position study ongoing Energy scale study ongoing

unfolded EPOS spectra by QGSJET2 spectra response ⇔ to determine the inelasticity, unsmeared spectra are important Next challenge; Spectra unfolding based on the bayesian statistics is ongoing smeared by the detector • The measured spectra were true energy (MC) measured (MC) ● unfolded spectra • Study of unfolding method LHCf preliminary E measure = AE true E true = A -1 E measure • The detector response trained A; Response matrix E measure ; Measured energy spectra E true ; True energy spectra

forward region of the LHC with √s=7TeV p-p collision known models (EPOS, QGSJET2, SYBILL, PYTHIA) Summary and plans • LHCf measured neutral baryons at the very • The energy spectra were compared with the • No model can explain our result perfectly • Study about systematic uncertainties is ongoing • Unfolding study is also ongoing

Spare slides

PID systematic error estimated from MC simulation reproduce the experimental data → some disagreement between data and MC estimate by another method (artificial method) is considered as systematic error → ～10% (depending on energy) 500-1000GeV • PID efficiency and purity are L 2D × ; Data 30000 ■ ; MC fit 25000 20000 • Scaling Photon/Hadron ratio to 15000 10000 5000 0 0 5 10 15 20 25 30 35 40 MC; Photon MC; Hadron 500-1000GeV L 2D • PID efficiency and purity was 35000 30000 25000 20000 15000 • Difference between the two methods 10000 5000 0 0 5 10 15 20 25 30 35 40

p T -Energy coverage • Expected p T -Energy spectra (EPOS) • Detector response not include hEvsPthadron_Small_True hEvsPthadron_Large_True hEvsPtThadron_Small hEvsPtThadron_Small hEvsPtThadron_Large hEvsPtThadron_Large Entries Entries 80134 80134 Entries 43829 Entries 43829 1 1 Mean x Mean x 2089 2089 Mean x 1226 Mean x 1226 800 Mean y 0.08944 Mean y 0.08944 Mean y 0.3085 Mean y 0.3085 0.9 0.9 872.3 872.3 RMS x 784.3 RMS x 784.3 800 RMS x RMS x 700 RMS y 0.1957 RMS y 0.1957 RMS y 0.05328 RMS y 0.05328 0.8 0.8 700 600 0.7 0.7 600 500 0.6 0.6 500 0.5 0.5 400 400 0.4 0.4 300 300 0.3 0.3 200 200 0.2 0.2 100 100 0.1 0.1 0 0 0 0 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500 LHCf Small tower LHCf Large tower

Vertex resolution large tower seems worse because the position resolution is defined as standard deviation of hitposition distribution Position 2.5~0.5 4.0~1.0 ↓ FWHM resolution mm mm 3 Fitting RMS[mm] 2.5 2 • The position resolution of LHCf Small tower 1.5 1 0.5 0 0 500 1000 1500 2000 2500 3000 3500 • Reason; Incident Energy[GeV] 3 Fitting RMS[mm] 2.5 2 LHCf Large tower 1.5 1 0.5 0 • Width itself is almost same 0 500 1000 1500 2000 2500 3000 3500 Incident Energy[GeV]