CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) J. Huang for the Tibet ASγ Collaboration Institute of high energy.

CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) J. Huang for the Tibet ASγ Collaboration Institute of high energy physics, Chinese Academy of Sciences China, Beijing Today, I would like to talk about “CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) ” Workshop Agenda, IHEP, CAS, Beijing, October , (2012)

Contents Knee of the spectrum.
Two Possible explanations for the sharp knee. New hybrid experiment (YAC+Tibet-III). Primary proton, helium spectra obtained by (YAC-I + Tibet-III). Expected results by (YAC-II + Tibet-III). Summary In this talk I would like to briefly summarize “Knee of the spectrum”, and “Two Possible explanations for the sharp knee”, and then I would like to introduce our “new hybrid experiment (YAC+ Tibet-III)”, ,and “Primary proton and helium spectra obtained by (YAC-I + Tibet-III) experiment” will be discussed with some details. Also I would like to talk about “Expected results by (YAC-II + Tibet-III) “ and “Summary”. J. Huang (Workshop Agenda, Beijing, China, (2012))

Tibet experiment 1014-1017 eV YAC Pb
The merit of the Tibet experiment is that the atmospheric depth of the experimental site (4300 m above sea level) is close to the maximum development of the air showers, with energies around the knee almost independent of the masses of primary cosmic rays as shown in this figure. Tibet experiment eV Merit of high altitude AS array at high altitude (4300m a.s.l.) Tibet-III array:37000m2 with 789 scint. YAC array: 500m2 with 124 scint. MD array: 5000m2 with 5 pools of water Cherenkov muon D.s . Measure:energy spectrum around the knee and chemical composition using sensitivity of air showers to the primary nuclei through detection of high energy AS core. YAC Pb Iron Scint. Box 7 r.l. The Tibet Air shower array experiment has been operating successfully at Yangbajing (4300m a.s.l.) in Tibet, China since At present, this array consists of detectors, and effective area for AS is about 37,000 m^2. The merit of the air-shower experiment in Tibet is that the atmospheric depth of the experimental site (4300 m Above sea level) is close to the maximum development of the air showers, with energies around the knee almost Independent of the masses of primary cosmic rays as shown in this figure. Tibet experiment is a hybrid experiment which consists of a core detector array (YAC detector array) and the air-shower array (Tibet-III) and Water Cherenkov muon D.s are under construction. This hybrid experiment are used to measure energy spectra around the knee and chemical composition using sensitivity of air showers to the primary nuclei through detection of high energy AS core. Altitude: 4300m a.s.l. Atomospheric depth: 606 g/cm2 J. Huang (Workshop Agenda, Beijing, China, (2012))

Tibet YAC array (Yangbajing Air shower Core arary)
Tibet-III: Energy and direction of air shower Cosmic ray(P,He,Fe…) Particle density & spread Separation of particles Tibet-III array is used to observe the total energy and the direction of an air shower and YAC observes high energy electromagnetic component around the air shower core. J. Huang (Workshop Agenda, Beijing, China, (2012))

All-particle spectrum measured by Tibet-III array
from ~1017eV (ApJ 678, (2008)) Model Knee Position (PeV) Index of spectrum QGS.+HD 4.0± 0.1 R1= -2.67± 0.01 R2= -3.10± 0.01 QGS.+PD 3.8± 0.1 R1= -2.65± 0.01 R2= -3.08± 0.01 SIB.+HD R2= -3.12± 0.01 The result of our measurement of all-particle energy spectrum covering three decades of energy range around the knee is shown in this Figure. The measurements in the highest energy range is also shown in this figure. 5 J. Huang (Workshop Agenda, Beijing, China, (2012)) 5/ 31 5 5

Energy spectrum around the knee measured by many experiments
　　Tibet　　　　　　　　　　　　KASCADE　　　　　　　　HEGRA Energy spectrum around the knee measured by many experiments are also shown in these figures. CASA/MIA　　　　　　　　BASJE　　　　　　　　　　　Akeno DICE J. Huang (Workshop Agenda, Beijing, China, (2012))

Normalized spectrum J. Huang (Workshop Agenda, Beijing, China, (2012))
When we normalized the all-particle energy spectrum at 10^15 eV, we found a sharp knee is clearly seen. J. Huang (Workshop Agenda, Beijing, China, (2012))

A sharp knee is clearly seen (ApJ 678, 1165-1179 (2008))
What is the origin of the sharp knee? There were many models: nearby source, new interaction threshold, etc. In the following, I would introduce our two analyses for the origin of the sharp knee. A sharp knee is clearly seen. Therefore we have a question, that is “what is the origin of the sharp knee ”, There were many models: nearby source, new interaction threshold, etc. In the following, we would introduce our two analyses for the origin of the sharp knee. 8 J. Huang (Workshop Agenda, Beijing, China, (2012)) 6/ 31 8

Two possible explanations for the sharp knee
( M. Shibata, J. Huang et al. APJ 716 (2010) 1076 ) For explaining the sharp knee we proposed two composition models (called Model A and Model B) that are based on: 1) the up-to-now available experimental results; 2) some physics (or theoretical) assumptions. For explaining the sharp knee we proposed two composition models (called Model A and Model B) that are based on: 1) the up-to-now available experimental results; 2) some physics (or theoretical) assumptions. 9 J. Huang (Workshop Agenda, Beijing, China, (2012)) 7/ 31 9

For ‘the up-to-now available experimental results’, we request:
a) In the enery region lower than 100 TeV the directly measured p, He, …, iron spectra by CREAM, ATIC, JACEE, RUNJOB etc should be smoothly connected by the modeling spectra; b) In the energy region higher than 100 TeV the modeling p and He spectra should be consistent with our indirectly measured p and He spectra; c) The superposed spectrum of all elemental spectra in the modeling should be consistent with our measured all-particle spectrum. J. Huang (Workshop Agenda, Beijing, China, (2012))

Some physics (or theoretical ) assumptions for both Model A and Model B
Diffusive shock acceleration in SNRs is assumed; Multiple galactic sources were considered. For each source there is an ‘acceleration limit’ ε(Z) which --- is proportional to the charge Z of accelerated nuclei, --- denotes the energy the accelerated particles start to deviate from the power law; εmax is introduced that denotes the ‘Maximum acceleration limit’ among multiple sources. Some physics (or theoretical) assumptions for both Model A and Model B J. Huang (Workshop Agenda, Beijing, China, (2012)) 8/ 28

In this physics picture the knee is caused by the‘minimum acceleration limit’ε(Z), (see details in the paper). Taking different ε(Z) and εmax the obtained all particle spectrum shows a smooth structure (see the figure below). The sharp knee cannot be produced. To explain the sharp knee we proposed two approaches, called Model A and Model B. (ApJ ,716: (2010)) J. Huang (Workshop Agenda, Beijing, China, (2012))

Model A: Sharp knee is due to nearby sources
(ApJ ,716: (2010)) Substracting the smooth spectrum from the measured all particle spectrum, a power-law spectrum with index -2 is obtained (see the dotted line in the figure) This is very consistent with the assumption of CR particles coming from nearby source(s). Extra component can be approximated by: J. Huang (Workshop Agenda, Beijing, China, (2012)) 9/ 28

Model B: Sharp knee is due to nonlinear effects in the defuse shock acceleration
It was suggested (Malkov & Drury 2001; Ptuskin & Zirakashvili 2006) that: In the diffuse shock acceleration mechanism, the nonliner effect at supernova shock fronts is present that may produce a harder cosmic ray spectrum in the source. We included this effect by introducing an additional term in our formalism that showed to produce a dip below the ‘minimum acceleration limit’ of the spectrum of each element (see the figure). J. Huang (Workshop Agenda, Beijing, China, (2012)) 10/ 28

Their superposition can well produce the all-particle spectrum including the sharp knee. (Model B)
(ApJ ,716: (2010)) J. Huang (Workshop Agenda, Beijing, China, (2012))

Two possible explanations for the sharp knee
( APJ 716 (2010) 1076 ) 2) Model B: Sharp knee is due to nonlinear effects in the diffusive shock acceleration (DSA) 1) Model A: Sharp knee is due to nearby sources In model A, sharp knee is due to nearby sources, in this model, and middle composition ( CNO ) is predicted at the knee. However, in Model B, sharp knee is due to nonlinear effects in the diffusive shock acceleration, in this model,and iron-dominant composition is predicted at the knee and beyond. All-particle knee = CNO? All-particle knee = Fe knee? J. Huang (Workshop Agenda, Beijing, China, (2012))

Short summary Two scenarios (model A and model B) are proposed to explain the sharpness of the knee. In model A, an excess component is assumed to overlap the global component, and its spectrum shape suggests that it can be attributed to nearby source(s) because it is surprisingly close to the expected source spectrum of the diffuse shock acceleration. CNO dominant composition is predicted by this model at the knee. In model B, a hard observed energy spectrum of each element from a given source is assumed. The sharp knee can be explained by a rigidity-dependent acceleration limit and hard spectrum due to nonlinear effects. Iron-dominant composition is predicted by this model at the knee and beyond. J. Huang (Workshop Agenda, Beijing, China, (2012)) 11/ 28

These aims will be realized by our new experiments
　　 In order to distinguish between Model A and Model B and many other models, measurements of the chemical composition around the knee, especially measurements of the spectra of individual component till their knee will be essentially important. Therefore, we planed a new experiment: 1) to lower down the energy measurement of individual component spectra to *10TeV and make connection with direct measurements; 2) to make a high precision measurement of primary p, He, …, Fe till 100 PeV region to see the rigidity cutoff effect. These aims will be realized by our new experiments YAC (Yangbajing AS Core array) ! J. Huang (Workshop Agenda, Beijing, China, (2012)) 15/ 31

YAC project (*10TeV -100 PeV)
ＹＡＣ YAC project consists of 3 phase experiment, that is YAC-I, YAC-II and YAC-III. J. Huang (Workshop Agenda, Beijing, China, (2012))

New hybrid experiment (YAC+Tibet-III+MD)
Proton Iron This hybrid experiment consists of low threshold Air shower core array (YAC) and Air Shower (AS ) array and Muon Detector ( MD ) . Pb 7 r.l. Scint. Iron MD AS YAC2 YAC2 will measure the primary energy spectrum of 4 mass groups of P, He, 4<A<40, A>40 at 50 TeV – 1016 eV range covering the knee. This hybrid experiment consists of low threshold Burst Dector grid (YAC) and Air Shower (AS ) array and Muon Detector ( MD ) . Tibet AS array is used to measure primary energy and incident direction, and YAC2 is used to measure high energy AS core within several x 10m from the axis, and Tibet MD array is used to measure number of muon. Therefore, this hybrid experiment (YAC+Tibet-AS + MD) will measure the primary energy spectrum of 4 mass groups of P, He, 4<A<40, A>40 at 50 TeV – 1016 eV range covering the knee. Tibet-AS (37000 m2) : Primary energy and incident direction. YAC-II ( 500 m2 ): High energy AS core within several x 10m from the axis. Tibet-MD ( 5000 m2 ) : Number of muon. The sensitivity of above measured quantities to the primary mass is used to separate primary nuclei into 4 groups of p, He, Medium, Fe-group. Tibet-III (37000 m2) : Primary energy and incident direction. YAC2 ( 500 m2 ): High energy AS core within several x 10m from the axis. Tibet-MD ( 5000 m2 ) : Number of muon. J. Huang (Workshop Agenda, Beijing, China, (2012)) 16/ 31 20

YAC Detector Observe shower electron size Pb
Iron Scint. Box 7 r.l. Observe shower electron size under lead plate (burst size Nb) induced by high energy E.M. particles at air-shower core. WLSF (wave length shifting fibers) is used to collect the scintillation light for the purpose of good uniformity. Two PMTs are used to cover wide dynamic range (1MIP is calibrated by single muon). For High gain PMT , Nb: 1 – MIPs For Low gain PMT , Nb: MIPs 50cm Plastic scintillaors (4cm×50×1cm, 20pcs) 80cm WLSf Each YAC is composed by a lead layer of 7 r.l. thickness and a plastic scintillator. YAC detectors are used to observe shower electron size under lead plate (burst size Nb) induced by high energy E.M. particles at air-shower core. WLSF (wave length shifting fibers) is used to collect the scintillation light for the purpose of good uniformity. Two PMTs are used to cover wide dynamic range (1MIP is calibrated by single muon). For High gain PMT , Nb: 1 – MIPs For Low gain PMT , Nb: MIPs Low gain PMT R5325 High gain PMT R4125 J. Huang (Workshop Agenda, Beijing, China, (2012))

YAC1 is well running now ( data taking started from 2009.04.01)
YAC1 consists of 16 YAC detectors, covering an area about 10 m^2. Total : 16 YAC detectors Effective area: 10 m2 J. Huang (Workshop Agenda, Beijing, China, (2012)) 19/ 31

Detector Calibration PMT linearity, use of LED light source;
2. Linearity of PMT+scintillator, a. probe calibration; b. accelerator beam calibration. We have done a detail detector calibration as shown by the following: We used LED light source to check PMT linearity. We used a) probe calibration and b) accelerator beam calibration to Check linearity of (PMT+ scintillator). J. Huang (Workshop Agenda, Beijing, China, (2012))

Probe Calibration ( The determination of the burst size is calibrated using single muon peak )
Single muon calibration 1 MIP Using a probe detector, we can obtain the single particle peak for each YAC detector. In order to record the electromagnetic showers of burst size from 1 to 10^6 particles, a wide dynamic range of PMT is required. For each PMT (high gain and low gain) used in YAC-I the linearity has been measured by Using LED light source and optical filters. In the test we fixed the positions of LED, filter and PMT. By using different filters we can get light of different intensity, and then, we can check The Linearity of PMTs. Using a probe detector, we can obtain the single particle peak for each YAC detector. 24 J. Huang (Workshop Agenda, Beijing, China, (2012))

PMT linearity In order to record the electromagnetic showers of burst size from 1 to 10^6 particles, a wide dynamic range of PMT is required. For each PMT (high gain and low gain) used in YAC-I the linearity has been measured by using LED light source and optical filters. In the test we fixed the positions of LED, filter and PMT. By using different filters we can get light of different intensity, and then, we can check the Linearity of PMTs. Dynamic range and linearity High gain PMT R4125 106 Proton PMT output charge [pC×0.25] 1MIP Nb_top Iron Using a probe detector, we can obtain the single particle peak for each YAC detector. In order to record the electromagnetic showers of burst size from 1 to 10^6 particles, a wide dynamic range of PMT is required. For each PMT (high gain and low gain) used in YAC-I the linearity has been measured by Using LED light source and optical filters. In the test we fixed the positions of LED, filter and PMT. By using different filters we can get light of different intensity, and then, we can check The Linearity of PMTs. 106MIPs Low gain PMT R5325 Input light Primary Energy (GeV) 1017 eV 25 J. Huang (Workshop Agenda, Beijing, China, (2012))

Electron beam calibration of YAC to get ADC count vs number of particles
Thin IC Thick IC YAC The Beam 106 MIPs Calibration of YAC detector has also been done using Beijing Electron-Positron Collider linac beam. BEPC: Beijing Electron-Positron Collider 17/ 28

Calibration using BEPC
The experimental sketch Saturation of PMT & Saturation of scintillator The accelerator-beam experiment shows a good linearity between the incident particle flux and YAC-ADC output below 5×106 MIPs. the saturation effect of the plastic scintillator satisfies YAC detector’s requirement. Thin IC The accelerator-beam experiment shows a good linearity between the incident particle flux and YAC-ADC output below 5×106 MIPs. the saturation effect of the plastic scintillator satisfies YAC detector’s requirement. Thick IC Number of particles (Beam) 18/ 28

Primary proton, helium spectra analysis
Hereafter , I would like to report “Primary proton, helium spectra analysis”. J. Huang (Workshop Agenda, Beijing, China, (2012))

- Full M.C. Simulation - Hadronic interaction model
CORSIKA (Ver ) – QGSJET2– – SIBYLL2.1– 　　 = Air Shower simulation = CORSIKA (QGSJET2, SIBYLL2.1) ( 1 ) Primary energy: E0 >1 TeV ( 2 ) All secondary particles are traced until their energies become 300 MeV in the atmosphere. ( 3 ) Observation Site : Yangbajing (606 g/cm2 ) 　　 = Detector simulation = Simulated air-shower events are reconstructed with the same detector configuration and structure as the YAC array using Epics (uv8.64) Primary composition model NLA (above-mentioned Nonlinear effects model ). HD model (Heavy Dominant model: see M. Shibata, J. Huang et al. APJ 716 (2010) 1076 ) We have carried out a detailed Monte Carlo simulation of air showers using the simulation code CORSIKA (version 6.204) including QGSJET2 and SIBYLL2.1 hadronic interaction models. For the primary particles, the Model B ( above-mentioned Nonlinear effects model) and heavy dominant (HD) models were used. All secondary particles are traced until their energies become 300 MeV in the atmosphere. Simulated air-shower events are reconstructed with the same detector configuration and structure as the YAC array using Epics (uv8.64). 29 J. Huang (Workshop Agenda, Beijing, China, (2012)) 20/ 28 29

Primary cosmic-ray composition spectrum assumed in MC
( M. Shibata, J. Huang et al. APJ 716 (2010) 1076 ) In this work, two primary composition models are used, the heayy dominant model (HD) and the non-linear accleration model (NLA), as shown in this Figure. The primary composition spectra is connected with the direct experiment in the low energy and consistent with the spectrum obtained from our old hybrid experimental results in the high energy. J. Huang (Workshop Agenda, Beijing, China, (2012))

The difference between NLA and HD model
NLA: ‘He rich’ model HD : ‘He poor’ model The proton spectrum of the two models is connected with the direct experiment in the low energy and consistent with the spectrum obtained from the Tibet (EC+AS) experiment in the high energy. The He spectrum of HD model coincides with the results from RUNJOB and ATIC-I, we called ‘He poor’ model. However, the He spectrum of NLA coincides with the results from JACEE, ATIC-II, CREAM, we called ‘ He rich’ model. The sum of all single-component spectra can reproduce the sharp knee in all particle spectrum. This hybrid experiment consists of low threshold Burst Dector grid (YAC) and Air Shower (AS ) array and Muon Detector ( MD ) . Tibet AS array is used to measure primary energy and incident direction, and YAC2 is used to measure high energy AS core within several x 10m from the axis, and Tibet MD array is used to measure number of muon. Therefore, this hybrid experiment (YAC+Tibet-AS + MD) will measure the primary energy spectrum of 4 mass groups of P, He, 4<A<40, A>40 at 50 TeV – 1016 eV range covering the knee. Tibet-AS (37000 m2) : Primary energy and incident direction. YAC-II ( 500 m2 ): High energy AS core within several x 10m from the axis. Tibet-MD ( 5000 m2 ) : Number of muon. The sensitivity of above measured quantities to the primary mass is used to separate primary nuclei into 4 groups of p, He, Medium, Fe-group. J. Huang (Workshop Agenda, Beijing, China, (2012)) 16/ 31 31

Core event selection Selected Events QGSJET+HD 216942 SIBYLL+HD 304785
Event selection condition for AS core event was studied by MC and following criteria were adopted to reject non core events whose shower axis is far from the YAC array. Nb>200, Nhit≧4, Nbtop ≧1500, Ne>80000 | AS axis by LDF – burst center| < 5 m Statistics of core events in MC simulation and experiment Live Time is days. Selected Events QGSJET+HD 216942 SIBYLL+HD 304785 QGSJET+NLA 80861 SIBYLL+NLA 64331 YAC1 5035 Event selection condition for AS core event was studied by MC and following criteria were adopted to reject non core events whose shower axis is far from the YAC array. Nb>200, Nhit≧4, Nbtop ≧1600, Ne>80000 | AS axis by LDF – burst center| < 5 m Statistics of core events in MC simulation and experiment are shown in this Table. J. Huang (Workshop Agenda, Beijing, China, (2012))

Core event selection Base on the above core event selection condition, we found the AS axis estimated by LDF is within 5 m from our YAC detector array. 105 <= Ne <= 106 R <= 5 m 3464/3483=99.5% R< 5m Base on the above core event selection condition, we found the AS axis estimated by LDF is within 5 m from the burst center. J. Huang (Workshop Agenda, Beijing, China, (2012))

Interaction model dependence in (YAC1+Tibet-III) experiment
These figures shows that QGSJET and SIBYLL, both models produce distribution shapes consistent with our experimental data. Air shower size (Ne) spectra Total burst size (sum Nb) spectra First, we would like to check the interaction model dependence in (YAC1+Tibet-III) experiment. The differential air shower size (Ne) spectra and total burst size (sumNb) spectra and the top burst size (Nbtop) spectra of high-energy core events and the mean lateral spread <NbR> spectra observed by YAC-I are shown to compare with the simulation results, respectively. These figures shows that QGSJET and SIBYLL, both models produce distribution shapes consistent with our experimental data. Top burst size (Nb_top)spectra Mean lateral spread (NbR)spectra

Primary proton, He spectra analysis
Identification of proton events ANN (a feed-forward artificial neural network) is used. Input event features: Ne, ΣNb, Nbtop, Nhit, <Rb>, < NbRb>, θ Classification: proton/others Primary energy determination E0=f(Ne,s) based on proton-like MC events In this work, the separation of the primary mass is realized by use of a feed-forward artificial neural network (ANN) method. The following 7 parameters are input to the ANN . Primary energy is determinate by using the correlation between shower size and primary cosmic ray energy Based on proton-like MC events. J. Huang (Workshop Agenda, Beijing, China, (2012))

Primary (P+He) separation by ANN
QGSJET Purity – 95.2% Efficiency – 62% P+He Other Nuclei SIBYLL Purity – 94.5% Efficiency – 63% Primary (P+He) separation by ANN for MC events as shown in this figure, together with the experimental results. One can see that, the experimental data is also in a good agreement with the MC prediction, and that the (P+He) induced events are clearly separated from other nuclei. When Tc value is set as 0.2, where the purity is about 95.2%, and the efficiency is about 62%. P+He Other Nuclei J. Huang (Workshop Agenda, Beijing, China, (2012))

Primary proton separation by ANN for MC events
QGSJET Purity – 79% Efficiency – 46% P roton Other SIBYLL Purity – 78% Efficiency – 40% Other P roton J. Huang (Workshop Agenda, Beijing, China, (2012))

Air shower size to primary energy
The primary energy (E0 ) of each AS event is determined by the air-shower size (Ne) which is calculated by fitting the lateral particle density distribution to the modified NKG function. Modified NKG function Hereafter , I would like to introduce how can I get primary energy. We used J. Huang (Workshop Agenda, Beijing, China, (2012))

Size resolution (MC Data) (based on QGSJET+HD model ) (1
Size resolution (MC Data) (based on QGSJET+HD model ) (1.0 ≦ sec(Θzenith) < 1.1 ) QGSJET＋HD Ne resoultion: ~7% (Ne>105 ) QGSJET+HD The correlation between the true shower size and the estimated shower size,is demonstrated in these figures. Here, true size in horizontal axis means particle number calculated for carpet array while perpendicular axis is the fit size for real array using NKG function. These two figues show that the true shower size is well reproduced by the estimated shower size and the shower size resolution is estimated to be 7 % for air shower size above 10 to five in the case of QGSJET, and 9 % in the case of SIBYLL model.

Primary energy determination
(1.) Energy Resolution – Proton like events ( for T<=0.4 & sec(theta) <=1.1 ) 1e+05 < Ne < 1e+06 Energy Resolution : 500TeV

Check the systematic errors by ANN
P+He Proton Helium The primary energy of (P+He)-like or P-like or Helium-like events is in a good agreement with the true primary energy spectrum. From this figure, one can see that, the primary energy of P-like events is in a good agreement with the true primary energy spectrum. J. Huang (ISVHECRI2012, Berlin, Germany)

(SΩ)eff calculated by MC (1)
Nb >= 200 Nhit >= 4 Nbtop >= 1500 Ne >= 80000

Primary (P+He) spectra obtained by (YAC1+Tibet-III)
preliminary On the basis of all the discussions above, we obtained the primary (P+He) spectra based on the QGSJET+NLA, QGSJET+HD, SIBYLL+NLA and SIBYLL+HD model, respectively, between 50 TeV and 3 PeV. The red circle is by QGSJET + HD model, and the blue circle is by SIBYLL + HD model. And the black triganle is by QGSJET+NLA model, and the gray triganle is by SIBYLL+NLA model. Form this fig. ,The interaction model dependence is less than 25% in absolute intensity, and the composition model dependence is less than 10% in absolute intensity. This figure shows that, (YAC1+Tibet-III) could measure (p+He) at > 50 TeV which is consistent with the results of the direct observations and our old Tibet-EC experimental results. J. Huang (Workshop Agenda, Beijing, China, (2012))

Primary proton , helium spectra obtained by (YAC1+Tibet-III)
preliminary preliminary On the basis of all the discussions above, we can also obtain the primary proton, helium spectra Based on QGSJET+HD, QGSJET+NLA, SIBYLL+HD and SIBYLL+NLA models, respectively. the red circle is by QGSJET + HD model, and the blue circle is by SIBYLL + HD model. And the black triganle is by QGSJET+NLA model, and the gray triganle is by SIBYLL+NLA model. Form this fig. ,The interaction model dependence is less than 25% in absolute intensity, and the composition model dependence is less than 10% in absolute intensity. This figure shows that, YAC1 could measure protons , heliums at > 50 TeV which is consistent with the results of the direct observations and our old Tibet-EC experimental results. J. Huang (Workshop Agenda, Beijing, China, (2012))

YAC2 is also well running now ( data taking started from 2011.8.1)
YAC-II Pb 50cm 80cm YAC-II is also well running now , data taking started from There are 124 YAC detectors, cover area is about 500 m^2. Total : 124 YAC detectors Cover area: ~ 500 m2 J. Huang (Workshop Agenda, Beijing, China, (2012)) 16/ 28

Expected results by (YAC2+Tibet-III)
YAC2 will measure the primary energy spectrum of 4 mass groups of P, He, 4<A<40, A>40 at 1014 – 1016 eV range covering the knee. Solid lines:input Symbols:reconstructed Expected primary energy spectra Expected results by YAC is shown in this figure for proton, helium and iron group. Therefore, we can separate primary nuclei into 4 groups of p, He, Medium, Fe-group with this new hybrid experiment. Expected number of protons , heliums and irons using HD model are : Proton (> 100 TeV) : 2300 events per one year; Helium (> 200 TeV): 800 events per one year; Iron (> 1000 TeV): events per one year. 46 J. Huang (Workshop Agenda, Beijing, China, (2012)) 46

Summary YAC1 shows the ability and sensitivity in checking the hadronic interaction models. (2) The experimental distribution, sumNb has the shape very close to the MC predictions of QGSJET+NLA, QGSJET+HD , SIBYLL+NLA and SIBYLL+HD. Some other quantities, such as Ne, Nb_top, <R> have the same behavior as well. (3) Some discrepancies in the absolute intensities are seen. Data normally shows a higher intensity than MC. Taking a more hard He spectrum as given by CREAM can improve this situation. A further study is going on. (YAC1+Tibet-III ) could measure protons and heliums spectra at > 50 TeV which is shown to be smoothly connected with direct observation data at lower energies and also with our previously reported results at higher energies. J. Huang (Workshop Agenda, Beijing, China, (2012))

(6) The interaction model dependence in deriving the primary proton,
We obtained the primary energy spectrum of proton, helium and (P+He) spectra between 50 TeV and 1 PeV , and found that the knee of the (P+He) spectra is located around 400 TeV. (6) The interaction model dependence in deriving the primary proton, helium and (P+He) spectra are found to be small (less than 25% in absolute intensity, 10% in position of the knee ), and the composition model dependence is less than 10% in absolute intensity, and various systematic errors are under study now ! (7) Next phase experiment YAC2 will measure the primary energy spectrum of 4 mass groups of P, He, 4<A<40, A>40 at 1014 – 1016 eV range covering the knee. J. Huang (Workshop Agenda, Beijing, China, (2012))

Thank you for your attention !!

CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) J. Huang for the Tibet ASγ Collaboration Institute of high energy.

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CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) J. Huang for the Tibet ASγ Collaboration Institute of high energy.

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Presentation on theme: "CR spectrum and composition measured by Tibet hybrid experiment (YAC+Tibet-III) J. Huang for the Tibet ASγ Collaboration Institute of high energy."— Presentation transcript:

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