Measurements of forward neutron and neutral pion productions with the LHCf detector

Transcription

1 Measurements of forward neutron and neutral ion roductions with the LHCf detector Gaku Mitsuka (University of Florence, INFN Firenze, JSPS fellow) MPI4-7 Nov. 4, Krakow

2 Outline Introduction and hysics motivations he LHCf detector Selected hysics results - π and energy sectra - Neutron energy sectra Ugrade of the LHCf detector towards ev Summary

3 Physics motivation (cosmic ray oint of view). Inelastic cross section large raid develoment small dee enetrating!. Inelasticity k = - lead / beam large raid develoment small dee enetrating!. Forward energy sectrum softer raid develoment harder dee enetrating! 4. Nuclear effects! 5. Extraolation to high energy recise measurements at lower energies are crucial (by OEM) neutron (~leading baryon) hoton or π -Pb collisions many data oints. Charge ratio (e.g. NA6)!. Multilicity number of muons in air shower sensitive to mass comosition Air-shower roduction roortional de/dη secial imortance in forward region

4 he LHCf coloration he LHCf coloration involves ~ members from institutes. Feb. 9 Jul. Jul. Ar.

5 he LHCf detectors LHCf-Arm (W)cm x cm(h) x cm(d) Samling calorimeter, 44X,.6λ wo-tower structure 4m LHCf-Arm wo indeendent detectors (Arm and Arm) are located in AN to measure the very forward articles: - η>8.7 w/o crossing angle and η>8.4 with crossing angle - <GeV at s=7ev. Samling calorimeter + osition sensitive detector. Charged articles are swet away due to the D magnet, so we can only observe neutral articles (hoton and neutron). Same detectors have been used since 9. 5 Position sensitive detector Arm : Scintillation fibers Arm : Silicon stri detector Si in Arm

6 resolution [mm resolution [mm Detector erformances (9) - 4 m 4 m 8 cm 6 cm n π γγ LHCf IP 4 SPS7 mm cal. with 6V 4 SPS7 5mm cal. with 6V Hadronic shower (MC) EM shower (MC) PID technique 4GeV hoton MC mm cal. ev neutron Fig. 8. Energy energy resolutions for each tower and arm. he filled (oen) lots show the beam test (MC) results. he squares are for the small tow 5 mm for Arm and Arm, resectively) and triangle lots are for the large tower of each arm (4 mm and mm for Arm and Arm, resec high gain mode resolution [% Position resolution energy 5 Energy resolution Small tower Large tower σ E /E ~ 4% because of.6λ energy Deviation[% true energy MC 4mm cal. Position Position resolution resolution Deviation[% Identification of incoming article by shower shae Events / () 5 LHCf π reconstruction 4 SPS7 5mm cal. with 45V 8 SPS7 mm cal. with 45V MC 5mm cal. LHCf-Arm 6 MC mm cal. Data, s=7ev 45V (Low Gain) true energy Fig. 7. Correlation between the rimary electron energy and the sum of the deosited energy (de) measured by the calorimeters. he squa results of the mm or 5 mm and 4 mm or mm calorimeters, resectively. he filled symbols show the beam test results while the oen s the MC simulations. he dotted lines in the uer anels show linear fits to the beam test results and the residuals from the fits are shown i lots of residuals, the triangles are shifted by 5 GeV to avoid overla. Black : X-lane Red : Y-lane Resolution [% Resolution [% Energy Resolution (arm) SPS7 4mm cal. with 6V MC mm cal. 6V (High Gain) energy Energy resolution Energy Resolution (arm) 4 SPS7 mm cal. with 45V SPS7 4mm cal. with 45V MC mm cal. MC 4mm cal. 45V (Low Gain) energy Resolution [% Resolution [% Energy Resolution (arm) SPS7 mm cal. with 6V MC 5mm cal. 6V (High Gain) energy Energy Resolution (arm) energy M γγ ~M π [MeV/c Fig. 9. Energy resolutions for each tower and arm. he filled (oen) lots show the beam test (MC) results. he circles are for the small tower of each M γγ

7 Udate of π analysis Present LHCf results are based on the ye-i π events. Imroved π reconstruction, ye-ii, is now ready for use in analysis. Motivation of ye-ii - extended range - alicable to Λ and K - di-hadron. Arm Geometry(Arm) accetance && for E>GeV ye-i π Arm Geometry(Arm) accetance && for E>GeV ye-ii π [GeV/c P PRD 86, 9 PRC 89, y E π - [GeV/c P his analysis Large ower Small ower 4 y 7 E π - Events Preliminary LHCf s=7ev π σ~4% M γγ

8 Neutral ion energy sectra (in each ) Preliminary (/σ..5.. < LHCf <. s=7ev Ldt=.68+.5nb (/σ < <.4 (/σ..5.4 < <.6.5. Energy Energy Energy (/σ < <.8 Energy (/σ..8 < < Energy 8 LHCf (stat.+syst.) DPMJE.5 QGSJE II- QGSJE II SIBYLL. EPOS.99 EPOS LHC PYHIA 8.85 DPMJE and PYHIA are harder than LHCf <. GeV, although comatible at low and low E. QGSJE II gives good agreement at < <. GeV and.8 < <. GeV. EPOS.99 agrees with LHCf at.4 < <.8 GeV. LHCf refers EPOS.99 than EPOS LHC.

9 Neutral ion sectra (in each energy) Preliminary (/σ < E [ev <.5 LHCf s=7ev Ldt=.68+.5nb (/σ < E [ev <.5 (/σ < E [ev <.75 (/σ < E [ev < (/σ < E [ev <.5 (/σ < E [ev <.5 (/σ < E [ev <.75 (/σ < E [ev < (/σ < E [ev < (/σ < E [ev < LHCf (stat.+syst.) DPMJE.5 QGSJE II- QGSJE II SIBYLL. EPOS.99 EPOS LHC PYHIA 8.85 Same conclusion as energy sectra in each.

10 Neutral ion sectra (in each y) Preliminary 8.6 < y < < y < < y < < y < 9.4 (/σ - LHCf s=7ev Ldt=.68+.5nb (/σ - (/σ - (/σ < y < < y < < y <.. < y < (/σ (/σ (/σ (/σ (/σ -. < y < (/σ -.4 < y < (/σ -.6 < y <.8 LHCf (stat.+syst.) DPMJE.5 QGSJE II- QGSJE II SIBYLL. EPOS.99 EPOS LHC PYHIA 8.85

11 Average and limiting fragmentation Preliminary LHCf π 8.6<y<8.8 sectra can be fitted by a Gaussian shae: E d d ¼ A exð = Gauss Þ : Gauss <> [GeV/c Data Best-fit Gaussian < > obtained by Gaussian fits. Other systematics will be quoted y beam -y ð hen the average < >is obtained by h i ¼ R fð Þd R fð Þd ¼ ffiffiffiffi Gauss; (Exonential Þ and sallis fail to fit the LHCf data.) dn/dy /N LHCf rovides a unique oortunity to test a limiting fragmentation (analysis ongoing but limited raidity ).. - EPOS.99 ev 7 ev.76 ev.9 ev π ev 7 ev.76 ev.9 ev neutron (x) - y-y beam dn/dy /N ev 7 ev.76 ev.9 ev QGSJE II π ev 7 ev.76 ev.9 ev neutron (x) - y-y beam

12 dσ n /de [mb/gev Neutron energy sectra he exected for r< cm, mean value with A. ADARE et al. PHYSICAL REVIEW D 88, 6 () ABLE I. the exerimental cut, and the efficiency for the exerimental cut estimated by the simulation (Fig. ). he errors were derived considering the uncertainty in the arameter aðx F Þ in the Gaussian -.6 form evaluated by HERA. Neutron x F Mean LHCf (GeV=c) s = 7 ev Efficiency η > DPMJE.4 :779 :4ð:8%Þ EPOS.99 :75 :9ð:%Þ PYHIA 8.45 :7 :6ð:8%Þ.9..4 QGSJE II- :68 :6ð:%Þ.4 SYBILL. ABLE III. he result of the differential cross section ffiffi d=dx F ðmbþ for neutron roduction in þ collisions at s ¼ GeV. he first uncertainty is statistical, after the unfolding, and the second is the systematic uncertainty. he absolute normalization error, %, is not included. hx F i Exonential form LHCf Gaussian s = 7 ev form..5 :4 :4 :4 DPMJE :94.4 : :7.68 :49 :9 :5 EPOS : :6 :85.8 :68 :44 :94 PYHIA : :44 : :4 :5 : QGSJE :9II- :7 :.6 SYBILL. are the efficiency for the exerimental cuts and are listed in.4 B. Result able I. he errors were derived considering the.. uncertainty in the arameter aðx F Þ in the Gaussian form he differential cross section, d=dx F, ffiffi for forward evaluated by HERA. here is no significant difference in neutron roduction in þ collisions at s ¼ GeV the result in case of using the ISR (exonential) was determined using two distributions: a Gaussian..8 distribution. form, as used in HERA analysis, and an exonential he mean values of the simulated distributions in form, used for ISR data analysis. he results are listed in.6 each energy region are also listed in able I. he cross able III and lotted in Fig.. We show the results for x F section.was obtained after the correction of the energy above.45 since.4 the data below.45 are significantly unfolding and the cut efficiency. affected by the energy cutoff before the unfolding. he. able II summarizes all systematic uncertainties evaluated as range in each x F bin is < < :x F GeV=c from the ratio 5of the variation 5 to the final cross 5section Eq. () with the accetance cut of r< cm. he absolute values. he absolute normalization error is not included Energy in normalization uncertainty for the PHENIX measurement, Energy these errors. It was estimated by BBC counts to be 9.7% 9.7%, is not included. (:9 : mb for the BBC trigger cross section). he background contamination (e+ at inhera) the measured neutron (+ at RHIC) energy withforward the ZDCNeutrons energy from 7 to 4 < W GeV < for GeV the.9 accetance cut of r< cm was estimated by the simulation with the PYHIA H s= GeV : PHENIX exonential form H Data SIBYLL event generator.. he background from.8 s= GeV : PHENIX gaussian form rotons.4 was estimated EPOS tolhc be.4% in the simulation. he systematic uncertainty QGSJE in theii exerimental data was determined to be.5 times QGSJE larger than this as discussed in.7 s=.6 GeV : ISR.6 s=44.9 GeV : ISR Sec. II. B. Multile QGSJE article detection (no mi) in each collision was estimated to be 7% with the r< cm cut. s=5.8 GeV : ISR.5 In the cross section analysis, we evaluated the beam s=6.7 GeV : ISR center shift described in Aendix A as a systematic.4 uncertainty.. For the evaluation, cross sections were calculated in the different accetances according to the result of. the beam center shift while requiring r< cm, and the variations were alied as a systematic uncertainty.. dσ/dx F /σ DIS. re-lhc models ABLE II. Systematic uncertainties for the cross section measurement. he absolute normalization error is not included in these errors. he absolute normalization uncertainty was estimated by BBC. counts.. to be.4 9.7%.5 (:9.6 : mb.7for.8 the BBC.9 trigger cross section). x F (H, Exonential Eur. Phys. J. C Gaussian (4)) form form distribution % % 7% % Beam center shift % % dσ/dx (mb). dσ n /de [mb/gev x F (PHENIX, Phys. Rev. D 88 6 ()) FIG. (color online). he cross section results ffiffi for forward neutron roduction in þ collisions at s ¼ GeV are shown. wo different forms, exonential (squares) and Gaussian (circles), were used for the distribution. Statistical uncertainties are shown as error bars for each oint, and systematic 8.99 < η < 9. dσ n /de [mb/gev LHCf s = 7 ev DPMJE.4 EPOS.99 PYHIA 8.45 QGSJE II- SYBILL. Preliminary 8.8 < η < Energy Focusing on the extreme forward region η>.76 - only QGSJE II- reroduces LHCf (more or less). Is this a signature of low-mass diffraction? - a similar shae with HERA, RHIC, and ISR data which can be exlained by a ion exchange. Can LHCf be also exlained by a ion exchange? Investigation in more wider raidity and energy ranges is needed to answer this question.

13 Ugrade of the LHCf detector Preliminary Main features of the ugrade LHCf detector GSO scintillator GSO hodoscoe (Arm) Udate of Si-stri sensor (Arm) - Bonding scheme - Insertion osition Readout Floating GND Readout trick to avoid a saturation. HRADC LHCf Arm e - beam good linearity Energy Silicon sensor Oct 4, SPS Events e - 5GeV/c e - GeV/c LHCf Arm e - beam σ/mean~.% good resolution 94 ADC ΣADC

14 Summary Extended range in the π analysis rovides a more reliable benchmark for hadronic interaction MC and theoretical model (CGC?). Large amount of neutron yield is found in extreme forward raidity which may be a signature of low-mass diffraction or ion exchange. Need exhaustive analysis. he ugraded LHCf detectors were calibrated by the SPS test beam. hey show a good and exected erformance. 4

15 Backu

16 Phys. Rev. D 86, 9 () Inclusive π sectra in - at 7eV c [GeV LHCf s=7ev π 8.9 < y < 9. Ldt=.5+.9nb c [GeV LHCf s=7ev π 9. < y < 9. Ldt=.5+.9nb c [GeV LHCf s=7ev π 9. < y < 9.4 Ldt=.5+.9nb Ed Ed Ed /σ - Data DPMJE.4 QGSJE II- SIBYLL. EPOS.99 PYHIA [GeV/c /σ [GeV/c /σ [GeV/c c [GeV LHCf s=7ev π 9.4 < y < 9.6 Ldt=.5+.9nb c [GeV LHCf s=7ev π 9.6 < y <. Ldt=.5+.9nb c [GeV LHCf s=7ev π. < y <. Ed Ldt=.5+.9nb /σ Ed Ed /σ /σ [GeV/c [GeV/c [GeV/c LHCf data are mostly bracketed among hadronic interaction models. DPMJE, SIBYLL(x) and PYHIA are aarently harder, while QGSJE is softer.

17 Phys. Rev. C 89, 659 (4) Inclusive π sectra in -Pb at 5.eV (/σ (/σ - LHCf s=5.ev π -8.9 > y > > y (a) > -9.6 (d) (/σ (/σ - DPMJE.4 QGSJE II- EPOS > y LHCf -Pb at 5.eV LHCf - at 5.eV (x5) > y > -9. (b) > -. (e) (/σ (/σ > y > y > -9.4 (c) >. (f) he LHCf data in -Pb (filled circles) show good agreement with DPMJE and EPOS. he LHCf data in -Pb are clearly broadened than the LHCf data in - at 5.eV (shaded area). he latter is interolated from the results at.76ev and 7eV. 7

18 Phys. Rev. C 89, 659 (4) R Pb ( ) Nuclear modification factor in -Pb at 5.eV R Pb R Pb hn coll i =6.9 (a) LHCf DPMJE.4 QGSJE II- EPOS (d) hn coll i Pb LHCf s=5.ev π -8.9 > y > > y > -9.6 R Pb R Pb Ed Pb /d Ed /d (b) -9. > y (e) -9.6 > y Both LHCf and MCs show strong suression. LHCf grows as increasing, which is understood by the softer sectra in - at 5eV than those in -Pb. 8 > > -. R Pb R Pb (c) -9. > y (f) -. > y > >.

19 Color Glass Condensate PRL, (4) PHYSICAL REVIEW LEERS - collisions at s = 7 ev week ending JANUARY 4 9.<y<9.4 dy -Pb collisions at s = 5. ev d dn/ - dy d..4.6 (GeV) P ffiffiffiffiffiffiffi FIG. (color (W.-. online). Deng et Predictions al., 4.8) for the yields at the LHC energy s NN ¼ 5. (A. ev M. Stasto in Pbet collisions, al., PRL both at LO and(4)) with NLO corrections included, using the.<y<. rcbk gluon distribution. On the left, we show results for π yields at η ¼ 6.75 (Y CM ¼ 5.9 in the center of mass frame) which falls in the range of seudoraidities detected by OEM, and on the right, for π yields at η ¼ (Y CM ¼ 8.) which falls in the range detected by LHCf. he edges of the solid bands were comuted by using μ ¼ GeV on the left and μ ¼ GeV on the right. - 9