HCAL1 performance in 2002

Oleg Gavrishchuk, JINR, Dubna HCAL1 performance in 2002 Chaliguine A.B., Gavrishchuk O.P., Ioukaev A.I., Kouzmine N.V., Maximov A.N., Savin I.A., Vlassov N.V. COMPASS note 2003-6 , September 19, 2003 1. INTRODUCTION 2. RECONSTRUCTION OF THE PARTICLE ENERGY IN HCAL1 2.1. THE SHAPE OF THE HADRON ENERGY SPECTRA IN HCAL1 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF THE TRACKS RECONSTRUCTED BY CORAL. 4. CALIBRATION OF THE HCAL1 USING RECONSTRUCTED MOMENTUM OF THE TRACK 5. SPACE RESOLUTION 6. MUONS IN HCAL1 7. HCAL1 STABILITY 8. CONCLUSIONS 9. REFERENCES

HCAL1 performance in 2002 • INTRODUCTION • The mini-DST of the period P2E, 2002 was used for the most studies. A stability of the HCAL1 energy reconstruction was checked using all available at Dubna mini-DST’s. • For the comparison of the energy reconstructed by HCAL1 with the momentum of incoming particle, the tracks with Ptrac>1.1GeV/c reconstructed by CORAL were used. • The tracks have been extrapolated to the front face of the HCAL1 (Z=1267.500). • “Cluster” is defined in CORAL as a group of adjacent modules each of which giving a signal above the certain threshold which is selected to be 1.2 GeV. Clusters may include one, two or more fired modules. • The “cluster size” (SC) on miniDST is defined as a number of adjacent modules containing 90% or more of the total cluster energy (Eclust). • The distances (DR) between the “center of gravity” of the HCAL1 clusters (xC, yC) and tracks (xT, yT) are calculated as: • Clusters with DR<15.5 cm corresponding to the dimensions of the HCAL1 module are considered as “associated” ones. DR distribution is shown in Fig.1, where vertical line corresponded to HCAL1 module size. • Multiplicities of the “associated” clusters for the period P2E are shown also in Fig.1. The average value of the “associated” clusters was <Nclust>=3 per event. Fig.1. Upper plot: The distributions of the distances (DR) between gravity clusters center (xC, yC) and the hits of associated tracks coordinates (xT, yT) founded by CORAL. Lower plot: The distribution of associated clusters multiplicities per event. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 The distribution of clusters with different sizes from SC=1 to SC=6 over the HCAL1 surface are shown in Fig.2. Note that clusters SC=1, i.e. clusters with 90% of the total energy deposited in one module, are distributed uniformly over the HCAL1 surface while the large size clusters are closer to the HCAL1 center window. Fig.2.The distributions of the associated clusters with sizes SC=1-6 over the HCAL1 surface. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.RECONSTRUCTION OF THE PARTICLE ENERGY IN HCAL1 2.1. THE SHAPE OF THE HADRON ENERGY SPECTRA IN HCAL1 • The energy calibration of HCAL1 has been performed earlier in the CERN test beam and results were communicated elsewhere [2]. In the energy range Ee,=10-100 GeV the calorimeter response was linear. • Testing and adjusting of all HCAL1 modules has been performed also using the halo muons COMPASS beam. • As for the test beam [2], the mean energy loss of the minimum ionizing particle (MIP) in the calorimeter module was found to be 1.76 GeV. • This value should be taken as a calibration constant for all HCAL1 modules and corresponding ADC’s. • But accidentally another calibration constant was taken during the DST production. • So, for the present analysis the cluster energies written on the miniDST were divided by a factor 1.25. • As result of the analysis this factor is corrected further. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 Fig.3.The energy distribution of all clusters (SC>0) recorded by HCAL1 during the Run No 22384, P2E with various COMPASS triggers. Statistics and percentage of the trigger types are indicated. • As easy one can look, the distributions in Fig.3 are irrespective to its in Fig.4. Fig.4.The energy distribution of associated clusters (SC>0) recorded by HCAL1 during the Run No 22384, P2E with various COMPASS triggers. Statistics and percentage of the trigger types are indicated. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 The superposition of the Fig.3 and Fig.4 is shown on Fig.5. Because these spectra statistics are different ones scaled by a given factor to compared shape of the distributions. The Eclust spectra are shown for different trigger type: IT, MT, OT, LT, MTC and look like similar. Fig.5.The comparison of energy distributions for all recorded by HCAL1 clusters (triangles) and associated clusters (histo): Fig.3 and Fig.4 superimposed. The spectra are scaled by the given factors. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 • As soon as we do not see trigger dependent anomalies in the comp-rison of the Eclust spectra with and without associated tracks, we have summed up the statistics and compared Eclust spectra for all clusters with SC>0, clusters with SC>2 ad clusters with SC>3 (Fig.5.a,b,c). • Two randomly chosen runs from periods P2E and P2G have been taken. The corresponding statistic is given in Table 1. Fig.5.a.The comparison of distributions the energy (Eclust) clusters recorded by HCAL1 with tracks (associated clusters) and without tracks (non-associated clusters) for the periods P2E (Run 22384) and P2G (Run 23017) for SC>0. Fig.5.b. The same as in Fig.5.a for the clusters size SC>2. Fig.5.c. The same as in Fig.5.a for the clusters size SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 Table 1. From the Figs 5a,b,c and from the Table 1 one can be conclude: • A fraction of clusters without associated tracks, amounting 85-90%, does not depend on the period of data recording and weakly depends on the cluster size. • Correspondingly, a fraction of clusters with associated tracks amount about 10-15% and rising with the increasing cluster size. • About 70% of clusters have a size SC=2 or SC=1, i.e. 90% of the energy corresponding to these clusters is contained in one or two adjacent modules. • The Eclust spectra for SC>2 and SC>3 with and without associated tracks have the similar shape, particularly the clusters with Eclust >5GeV. • This indicates they are the similar nature. Clusters without associated tracks can appears due to: • inefficiency of the program track reconstructions, • neutral hadrons (neutrons) produced in the COMPASS target, • accidentals. But last two sources cannot give such a big number of non-associated clusters. P2G, RUN 23017 P2E, RUN 22384 O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 • The associated clusters energy (Eclust) distributions for the whole period P2E are shown in Fig.6 for each trigger type. • The Eclust spectra for the MCT, OT and LT triggers look similar while MT and IT spectra are different from the former ones. Fig.6.The energy distributions for all clusters (SC>0) recorded during the whole period P2E with various triggers: MCT-histogram, OT-circles, LT-triangles, MT-squares, IT-open circles. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.7-12 (SC>0) together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.7. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>0 and Ptrack=5-5.5 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.7-12 (SC>0) together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.8. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>0 and Ptrack=7-7.5 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.7-12 (SC>0) together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.9. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>0 and Ptrack=10-11 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.13-18 (SC>3)together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.13. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>3 and Ptrack=5-6.5 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.13-18 (SC>3)together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.14. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>3 and Ptrack=7-7.5 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 2.2. THE UNIFORMITY OF THE ENERGY RECONSTRUCTION OVER THE HCAL1 SURFACE The uniformity of the energy reconstruction over the HCAL1 surface was studied dividing the HCAL1 in 10 regions (4 below, 4 above the central window, 1 left and 1 right of the window) and selecting the associated tracks in narrow Ptrack intervals (5-5.5, 7-7.5, 10-11, 15-16, 20-21, 25-26 GeV/c). Distributions of all reconstructed clusters for these regions and momentum intervals are shown in: Figs.13-18 (SC>3)together with the Gaussian fits of peaks. As it is seen from the plots, in every region the Eclust is very close to the center of the selected Ptrack intervals. So, the energy response of the HCAL1 is independent of the coordinate of the cluster. The widths of the Gaussian fits within precision of the present analysis are the same for each region. This indicates that the energy resolution of the HCAL1 is uniform over the calorimeter surface. Comparing the corresponding plots, one can conclude that the calorimeter responses do not depend on the choice of the cluster size. Fig.15. Distributions of the Eclust for associated tracks obtained in various HCAL1 regions for the cluster size SC>3 and Ptrack=10-11 GeV/c. Gaussians fits are shown by solid lines. The mean values and sigmas are given in the stat-boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF TRACKS RECONSTRUCTED BY CORAL. • Due to the facts that the HCAL1 characteristics do not depend on the position of the associated track, one can sum up the corresponding plots of Figs. 7-12 and Figs.13-18 and obtain plots showing the energy spectra of reconstructed clusters in the whole calorimeter for SC>0 and SC>3 (Fig.19a,b). • On the Fig.19,a plots for SC>0, except the Eclust peak at Ptrack corresponding to the momentum of hadrons, one can see the peaks at Eclust about 2 GeV corresponding to the energy deposited in the HCAL1 modules by MIP, i.e. by muons. • These peaks disappear (Fig.19,b) as soon as we require clusters to be SC>3, because most of muons deposits the energy in one or two adjacent modules depending on the muon coordinate within the dimensions of the module. • The correlations between Eclust and Ptrack have been seen already in Figs.7-18 and Fig.19.a,b. In the last Fig. the correlations between position of the Gaussian peaks vs Ptrack are shown for cluster size SC>0 and SC>3. These correlations are fitted by the straight lines: • Eclust=A+P*Ptrack [GeV/c] • with result: • Eclust=(-0.10.2)+(0.950.01)*Ptrack[GeV/c] for SC>0 Fig.19.a.The Eclust spectra reconstructed in the HCAL1 for different intervals of Ptrack:5-5.5, 7-7.5, 10-11, 15-16, 20-21, 30-31, 35-36 GeV/c and two-dimensional plot: Eclust vs Ptrack together with the linear fit. Eclust = A + P * Ptrack[GeV/c] Clusters SC>0. Gaussians fits are shown by solid lines. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF TRACKS RECONSTRUCTED BY CORAL. • Due to the facts that the HCAL1 characteristics do not depend on the position of the associated track, one can sum up the corresponding plots of Figs. 7-12 and Figs.13-18 and obtain plots showing the energy spectra of reconstructed clusters in the whole calorimeter for SC>0 and SC>3 (Fig.19a,b). • On the Fig.19,a plots for SC>0, except the Eclust peak at Ptrack corresponding to the momentum of hadrons, one can see the peaks at Eclust about 2 GeV corresponding to the energy deposited in the HCAL1 modules by MIP, i.e. by muons. • These peaks disappear (Fig.19,b) as soon as we require clusters to be SC>3, because most of muons deposits the energy in one or two adjacent modules depending on the muon coordinate within the dimensions of the module. • The correlations between Eclust and Ptrack have been seen already in Figs.7-18 and Fig.19.a,b. In the last Fig. the correlations between position of the Gaussian peaks vs Ptrack are shown for cluster size SC>0 and SC>3. These correlations are fitted by the straight lines: • Eclust=A+P*Ptrack [GeV/c] • with result: • Eclust=(+0.10.2)+(0.970.01)*Ptrack[GeV/c] for SC>3 Fig.19.b.The Eclust spectra reconstructed in the HCAL1 for different intervals of Ptrack:5-5.5, 7-7.5, 10-11, 15-16, 20-21, 30-31, 35-36 GeV/c and two-dimensional plot: Eclust vs Ptrack together with the linear fit. Eclust = A + P * Ptrack[GeV/c] Clusters SC>3. Gaussians fits are shown by solid lines. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF TRACKS RECONSTRUCTED BY CORAL. • Due to the facts that the HCAL1 characteristics do not depend on the position of the associated track, one can sum up the corresponding plots of Figs. 7-12 and Figs.13-18 and obtain plots showing the energy spectra of reconstructed clusters in the whole calorimeter for SC>0 and SC>3 (Fig.19a,b). • On the Fig.19,a plots for SC>0, except the Eclust peak at Ptrack corresponding to the momentum of hadrons, one can see the peaks at Eclust about 2 GeV corresponding to the energy deposited in the HCAL1 modules by MIP, i.e. by muons. • These peaks disappear (Fig.19,b) as soon as we require clusters to be SC>3, because most of muons deposits the energy in one or two adjacent modules depending on the muon coordinate within the dimensions of the module. • The correlations between Eclust and Ptrack have been seen already in Figs.7-18 and Fig.19.a,b. In the last Fig. the correlations between position of the Gaussian peaks vs Ptrack are shown for cluster size SC>0 and SC>3. These correlations are fitted by the straight lines: • Eclust=A+P*Ptrack [GeV/c] • with result: • Eclust=(+0.10.2)+(0.970.02)*Ptrack[GeV/c] for SC>0 and SC>3 Fig.21.The Eclust vs Ptrack plots for all events detected by HCAL1 in the period P2E: Upper plot is for clusters SC>0, lower plot is for clusters SC>3. So, within the quoted errors, the linear response of the HCAL1 in the rangePtrack = 5-35 GeV/c do not depend on the definition of the cluster size. The Eclust vs Ptrack correlation lines are shown in Fig.21 together with the P2E events distributions. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 Comparing the plots for SC>0 and SC>3 at the same Ptrack, one can conclude that SC>3 clusters are better determined, they have less background and Gaussian widths of peaks are closer to the expected ones determined in the test beams (see Fig.20). Fig.20. The HCAL1 energy resolution in the test beams [2] (magenta circles) and from Fig.19 (red squares) as function of the beam particles energy. We assume that at these energies E  Ptrack. The HCAL1 energy resolution in the test beams [2]: = (7.6+/-0.4) Gaussian fits parameters were used from Fig.19.a and Fig.19.b to obtain HCAL1 energy resolution as Sima/Mean. Upper plot is for SC>0, lower one is for SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF TRACKS RECONSTRUCTED BY CORAL. The direct comparison of Eclust and Ptrack distributions for various cluster sizes are shown in Fig.22. We assume that at these energies Eclust  Ptrack. From this Fig, one can see that the present algorithm of the cluster definition works better for SC=3 and SC=4: the shapes of spectra are similar. At SC<3 there is a big difference in the spectra at low Eclust while at SC>4 the shapes of Eclust and Ptrack spectra are different everywhere. The same features are better seen from Fig.23. From this Fig. one can conclude that, for the present algorithm, at Eclust >10GeV the shapes of spectra are almost identical and do not depend on the cluster size. At Eclust10 GeV clusters with SC>3 are better reproduce the Ptrack spectrum of events reconstructed by CORAL. Fig.22. The Eclust spectra for the clusters size SC=1,2,3,4,5,6 (histograms) and correspondingmomentum (Ptrack) spectra of the associated tracks (triangles) are shown on the plots. Fig.23. The same as in Fig.22 but for the sum of several cluster with sizes: SC>0, SC>2 , SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 3. CORRELATIONS OF ENERGIES RECONSTRUCTED IN HCAL1 AND MOMENTA OF TRACKS RECONSTRUCTED BY CORAL. One can ask how the Eclust vs Ptrack comparison depends on the COMPASS trigger type? Fig.24 answers this question: for Eclust >10 GeV the Eclust and Ptrack spectra look similar for all type of triggers, the cluster size SC>3 spectra are better reproduce the Ptrack spectra for all type of triggers. The direct Eclust vs Ptrack comparison of various triggers was performed also in 10 HCAL1 selected regions for clusters SC>0 (see Fig.25-30) and clusters SC>3 (Figs.31-36). No peculiarities are observed different from that of Fig.24. SC>0 SC>3 Fig.24.a. Comparison of the Eclust (histo) and Ptrack (triangles) spectra obtained wit different triggers for clusters SC>0. Fig.24.a. The same as in (a) but for SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 SC>0, IT SC>0, MCT SC>0, LT The direct Eclust vs Ptrack comparison of various triggers was performed also in 10 HCAL1 selected regions for clusters SC>0 and shown on Fig.25-30. No peculiarities are observed different from that of Fig.24. SC>0, OT SC>0, MT SC>0, ALL Fig.25-30. Comparison of the Eclust (histo) and Ptrack (triangles) spectra in the different regions of the HCAL1 with the IT triggers for SC>0. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 SC>3, IT SC>3, MCT SC>3, LT The direct Eclust vs Ptrack comparison of various triggers was performed also in 10 HCAL1 selected regions for clusters SC>3 and shown on Fig.31-36. No peculiarities are observed different from that of Fig.24. One can summarize the studies of this section as follows: The response of the HCAL1 is linear, uniform over the calorimeter surface and do not depend on the cluster size and type of the COMPASS trigger. SC>3, OT SC>3, MT SC>3, ALL Fig.31-36. Comparison of the Eclust (histo) and Ptrack (triangles) spectra in the different regions of the HCAL1 with the IT triggers for SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 4. CALIBRATION OF THE HCAL1 USING RECONSTRUCTED MOMENTUM OF TRACKS • The plots Eclust vs Ptrack, cluster size SC>0 and SC>3, for various regions of the HCAL1 are shown in Fig.37,a,b and for the whole calorimeter in Fig.38 together with linear fits: • Eclust=A+P*Ptrack[GeV/c]. • Within precision of the present analysis, all values of A and P are consistent. This is a quantitative measure of the HCAL1 uniformity on the energy response. • The values of the parameter P should be equal to 1 for the perfect calibration of the HCAL1. But the averaged P value is equal to: • P=0.960.01 over the HCAL1 regions. • So, the reconstructed energy which is written on the miniDST’s of 2002 should be corrected further. The additional to the factor 1.25, already applied for the described analysis, a factor 0.96 should be applied in average to all clusters. So, to obtain the correct energy for the clusters of HCAL1, the energy written on the miniDST’s must be divided by the factor:1.25:0.96=1.3. Fig.37.a. The linear fits of clusters energy (Eclust) as a function of the reconstructed momentum (Ptrack) for associated tracks hitting in the different HCAL1 regions for the clusters SC>0. The fit parameters are given in corresponding stat boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 4. CALIBRATION OF THE HCAL1 USING RECONSTRUCTED MOMENTUM OF TRACKS • The plots Eclust vs Ptrack, cluster size SC>0 and SC>3, for various regions of the HCAL1 are shown in Fig.37,a,b and for the whole calorimeter in Fig.38 together with linear fits: • Eclust=A+P*Ptrack[GeV/c]. • Within precision of the present analysis, all values of A and P are consistent. This is a quantitative measure of the HCAL1 uniformity on the energy response. • The values of the parameter P should be equal to 1 for the perfect calibration of the HCAL1. But the averaged P value is equal to: • P=0.960.01 over the HCAL1 regions. • So, the reconstructed energy which is written on the miniDST’s of 2002 should be corrected further. The additional to the factor 1.25, already applied for the described analysis, a factor 0.96 should be applied in average to all clusters. So, to obtain the correct energy for the clusters of HCAL1, the energy written on the miniDST’s must be divided by the factor:1.25:0.96=1.3. Fig.37.b. The linear fits of clusters energy (Eclust) as a function of the reconstructed momentum (Ptrack) for associated tracks hitting in the different HCAL1 regions for the clusters SC>3. The fit parameters are given in corresponding stat boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 4. CALIBRATION OF THE HCAL1 USING RECONSTRUCTED MOMENTUM OF TRACKS • The plots Eclust vs Ptrack, cluster size SC>0 and SC>3, for various regions of the HCAL1 are shown in Fig.37,a,b and for the whole calorimeter in Fig.38 together with linear fits: • Eclust=A+P*Ptrack[GeV/c]. • Within precision of the present analysis, all values of A and P are consistent. This is a quantitative measure of the HCAL1 uniformity on the energy response. • The values of the parameter P should be equal to 1 for the perfect calibration of the HCAL1. But the averaged P value is equal to: • P=0.970.02 over the HCAL1 regions. • So, the reconstructed energy which is written on the miniDST’s of 2002 should be corrected further. The additional to the factor 1.25, already applied for the described analysis, a factor 0.96 should be applied in average to all clusters. So, to obtain the correct energy for the clusters of HCAL1, the energy written on the miniDST’s must be divided by the factor: 1.25:0.96=1.3 (1.73+/-0.04 – should be MIP). Fig.38. The linear fit of the clusters energy (Eclust) as a function of the reconstructed momentum (Ptrack) for associated tracks hitting in the HCAL1: upper plot is for the clusters SC>0, lower one is for the clusters SC>3. The fit parameters are given in corresponding stat boxes. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 5. SPACE RESOLUTION • Remind, for the HCAL1 modules space resolution has been determined in the test beam [2] and found to be xy=14 mm. • Plots, which can characterize the HCAL1 space resolution in the real experimental conditions (data taking), are presented in Fig.39. The differences distributions (xC-xT) and (yC-yT) are shown for various cluster sizes and energies, where xC, yC are the coordinates of the clusters gravity center and xT, yT are the associated tracks ones. • These distributions was done by two Gaussians fit with parameters Const1, Mean1, Sigma1 and Const2, Mean2, Sigma2: • the first one describes the central part of the distributions, • the second one describes the peripheral part of distributions. • One can see that Sigma1 varies from 2.2 to 4.9 cm depending on the cluster size and energy. • The Sigma2 varies from 4.9 to 8.9 cm. • For the same clusters size Sigma1 decreases with increasing Eclust but Sigma2 remains constant. • The origin of two Gaussians is not understood yet. Probably it is connected with the present cluster search algorithm. Fig.39.a. The distributions of differences between coordinates of clusters and associated tracks at various energies and cluster sizes for X coordinates. Solid lines show two Gaussians fits. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 5. SPACE RESOLUTION • Remind, for the HCAL1 modules space resolution has been determined in the test beam [2] and found to be xy=14 mm. • Plots, which can characterize the HCAL1 space resolution in the real experimental conditions (data taking), are presented in Fig.39. The differences distributions (xC-xT) and (yC-yT) are shown for various cluster sizes and energies, where xC, yC are the coordinates of the clusters gravity center and xT, yT are the associated tracks ones. • These distributions was done by two Gaussians fit with parameters Const1, Mean1, Sigma1 and Const2, Mean2, Sigma2: • the first one describes the central part of the distributions, • the second one describes the peripheral part of distributions. • One can see that Sigma1 varies from 2.2 to 4.9 cm depending on the cluster size and energy. • The Sigma2 varies from 4.9 to 8.9 cm. • For the same clusters size Sigma1 decreases with increasing Eclust but Sigma2 remains constant. • The origin of two Gaussians is not understood yet. Probably it is connected with the present cluster search algorithm. Fig.39.b. The distributions of differences between coordinates of clusters and associated tracks at various energies and cluster sizes for Y coordinates. Solid lines show two Gaussians fits. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 5. SPACE RESOLUTION • Remind, for the HCAL1 modules space resolution has been determined in the test beam [2] and found to be xy=14 mm. • Plots, which can characterize the HCAL1 space resolution in the real experimental conditions (data taking), are presented in Fig.39. The differences distributions (xC-xT) and (yC-yT) are shown for various cluster sizes and energies, where xC, yC are the coordinates of the clusters gravity center and xT, yT are the associated tracks ones. • These distributions was done by two Gaussians fit with parameters Const1, Mean1, Sigma1 and Const2, Mean2, Sigma2: • the first one describes the central part of the distributions, • the second one describes the peripheral part of distributions. • One can see that Sigma1 varies from 2.2 to 4.9 cm depending on the cluster size and energy. • The Sigma2 varies from 4.9 to 8.9 cm. For the same clusters size Sigma1 decreases with increasing Eclust but Sigma2 remains constant. The origin of two Gaussians is not understood yet. Probably it is connected with the present cluster search algorithm. • Variations of xC-xT and yC-yT distributions over the HCAL1 surface are shown in Fig.40: Sigma1 and Sigma2 are the same values within errors for each HCAL1 region. Fig.40.a. The distributions of differences between clusters and associated tracks coordinate in various HCAL1 regions at Eclust>10 GeV : for xC-xT. Solid lines show two Gaussians fit. The smaller Sigma are corresponded to the HCAL1 central parts. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 5. SPACE RESOLUTION • Remind, for the HCAL1 modules space resolution has been determined in the test beam [2] and found to be xy=14 mm. • Plots, which can characterize the HCAL1 space resolution in the real experimental conditions (data taking), are presented in Fig.39. The differences distributions (xC-xT) and (yC-yT) are shown for various cluster sizes and energies, where xC, yC are the coordinates of the clusters gravity center and xT, yT are the associated tracks ones. • These distributions was done by two Gaussians fit with parameters Const1, Mean1, Sigma1 and Const2, Mean2, Sigma2: • the first one describes the central part of the distributions, • the second one describes the peripheral part of distributions. • One can see that Sigma1 varies from 2.2 to 4.9 cm depending on the cluster size and energy. • The Sigma2 varies from 4.9 to 8.9 cm. For the same clusters size Sigma1 decreases with increasing Eclust but Sigma2 remains constant. The origin of two Gaussians is not understood yet. Probably it is connected with the present cluster search algorithm. • Variations of xC-xT and yC-yT distributions over the HCAL1 surface are shown in Fig.40: Sigma1 and Sigma2 are the same values within errors for each HCAL1 region. Fig.40.b. The distributions of differences between clusters and associated tracks coordinate in various HCAL1 regions at Eclust>10 GeV : for yC-yT. Solid lines show two Gaussians fit. The smaller Sigma are corresponded to the HCAL1 central parts. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 6. MUONS IN HCAL1 We define as a muon the particle, trajectory of which is reconstructed by CORAL, hits in the HCAL1 and has a continuation in the MW1. In the MW1 we require to see at least two hits before and two hits behind in the iron absorber. The distance (dr) between coordinates of the track entering in the HCAL1 (xT, yT) and coordinates of the hits in the MW1 (x,y) is calculated as: Fig.41.Plot characterizing ALL muons passed through the HCAL1: • distribution of the distances (dr) between the track coordinates in HCAL1 (xT, yT) and hits coordinates (x,y) in MW1; • dr vs Ptrack two-dimensional plot; • Ptrack distribution; • Eclust distribution; Landau fit shown by solid line. • Eclust vs Ptrack two-dimensional plot; • Charge of “muons” vs Ptrack two-dimensional plot; • yT vs xT for associated clusters two-dimensional plot. • All muon spectra in HCAL1 O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 6. MUONS IN HCAL1 We define as a muon the particle, trajectory of which is reconstructed by CORAL, hits in the HCAL1 and has a continuation in the MW1. In the MW1 we require to see at least two hits before and two hits behind in the iron absorber. The distance (dr) between coordinates of the track entering in the HCAL1 (xT, yT) and coordinates of the hits in the MW1 (x,y) is calculated as: Fig.42.Plot characterizing NOT SCATTERING muons passed through the HCAL1: • distribution of the distances (dr) between the track coordinates in HCAL1 (xT, yT) and hits coordinates (x,y) in MW1; • dr vs Ptrack two-dimensional plot; • Ptrack distribution; • Eclust distribution; Landau fit shown by solid line. • Eclust vs Ptrack two-dimensional plot; • Charge of “muons” vs Ptrack two-dimensional plot; • yT vs xT for associated clusters two-dimensional plot. • All muon spectra in HCAL1 O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 6. MUONS IN HCAL1 We define as a muon the particle, trajectory of which is reconstructed by CORAL, hits in the HCAL1 and has a continuation in the MW1. In the MW1 we require to see at least two hits before and two hits behind in the iron absorber. The distance (dr) between coordinates of the track entering in the HCAL1 (xT, yT) and coordinates of the hits in the MW1 (x,y) is calculated as: The number of the scatering muons is small (<0.3%), dr is about 10 cm and all of them enter in the sides of the HCAL1 window. Fig.42.Plot characterizing SCATTERING muons passed through the HCAL1: • distribution of the distances (dr) between the track coordinates in HCAL1 (xT, yT) and hits coordinates (x,y) in MW1; • dr vs Ptrack two-dimensional plot; • Ptrack distribution; • Eclust distribution; Landau fit shown by solid line. • Eclust vs Ptrack two-dimensional plot; • Charge of “muons” vs Ptrack two-dimensional plot; • yT vs xT for associated clusters two-dimensional plot. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 7. HCAL1 STABILITY • The mean slope (tmean) of the Eclust spectra was determined for the whole period (middle picture from Fig.45). • The ratios: • R=t/tmean, where: • t=t–tmean • are shown in Fig.45 for the whole period P2E together with the Gaussian fits. The shape of the energy spectra, from which the slope tmean is determined, is shown at the center of the Fig.45 (middle picture). • The stability of the HCAL1 performance in 2002 has been tested using slopes (t) of the energy spectra at Eclust >5GeV and SC>3 for each run. • The stability of the ratio R vs Run No is shown in Fig.46 for one of the HCAL1 region (corresponding to lower right hand plot of Fig.45). Fig.45. The distributions of the ratio (R=t/tmean) ar e shown in various HCAL1 regions calculated at the energy (Eclust) spectra and cluster size SC>3. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 7. HCAL1 STABILITY • The stability of the ratio R vs Run No is shown in Fig.46 for one of the HCAL1 region (corresponding to lower right hand plot of Fig.45). • As it is seen from Fig.46, R is rather stable for P2E periods 2002. • The R varies within less than 5%, except one point. • The stability of the reconstructed Eclust spectra for various periods of the 2002 run is shown in Fig.47. The spectra at different periods are scaled by some factors for better comparison. Fig.46. Dependences of the ratio R vs Run No in the period P2E for one HCAL1 region (corresponding to the lower right hand spectrum of the Fig.45). O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 7. HCAL1 STABILITY • The R varies within less than 5%, except one point. • The stability of the reconstructed Eclust spectra for various periods of the 2002 run is shown in Fig.47. • The spectra at different periods are scaled by some factors for better comparison. Fig.47. The Eclust distributions for various periods of the 2002 RUN. The spectra ere scaled by the given factor. O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002 8. CONCLUSIONS • The linear energy HCAL1 response has been confirmed with the real data detected by COMPASS. • The true energy of hadrons detected by HCAL1 is equal to the energy written on miniDST’s divided by the factor 1.3. • The quality of the present algorithm of the cluster finding should be studied further. • Muon identification in HCAL1 will be studied further also. • The difference in the numbers of associated and not associated clusters should understand. • In the year 2002 HCAL1 has performed stable. 9. REFERENCES [1] http://coral.web.cern.ch/coral/ [2] http://wwwcompass.cern.ch/compass/transparencies/CALORIMETRY-1/HCAL-1.ps.gz [3] http://wwwcompass.cern.ch/compass/detector/trigger/welcome.html O.Gavrishchuk, COMPASS Collaboration Meeting

HCAL1 performance in 2002