H8 crystal data analysis 16/05/2014 ColUSM meeting Roberto Rossi Daniele Mirarchi, Stefano Redaelli, Walter Scandale, Gianluca Cavoto Table of contents Introduction H8 crystal run Analysis example Alignment run High statistic run Geometrical and angular cuts Torsion correction Channeling efficiency analysis Dechanneling length Transition region Population analysis Angular scan run Volume capture population analysis Conclusions R. Rossi - H8 crystal data analysis2 16/05/14 H8 Crystal test Beam The UA9 collaboration is studying techniques to steer ultra-relativistic beams with bent crystals to improve the collimation of proton and heavy ion beams at the LHC. Measurements of key crystals properties (bending angle, channeling efficiency, etc..) are performed on the SPS extraction line (H8) with 400 GeV/c protons before testing crystals with circulating beams. Scope of my master thesis work: Consistently analyze all the crystals tested in H8 (total of 15 between ). - Compile a comprehensive statistical treatment of different crystals - Identify fine systematic effects (e.g., transitions) - provide inputs to crystal code developers Immediate goal: compile list of experimental data for an upcoming workshop on crystal simulations. 3R. Rossi - H8 crystal data analysis 16/05/14 H8 experimental Layout Five silicon micro-strip sensors (active area 3.8x3.8 cm 2 in the x-y plane) are used to track the particles in the plane orthogonal to the beam direction before and after passing through the crystal. 4R. Rossi - H8 crystal data analysis [1] M. Pesaresi et al., Design and performance of a high rate, high angular resolution beam telescope used for crystal channeling studies,2011 JINST 6 P /05/14 Track reconstruction Only one track per event is reconstructed. The event reconstruction uses the first two and the last two detectors to measure the incoming and the outgoing angle of the tracks, respectively. The impact point at the crystal position is given by the interpolation of the incoming and the outgoing tracks. 5R. Rossi - H8 crystal data analysis 16/05/14 Experimental data structure A complete experimental characterization of a crystal consists of different acquisition runs Alignment run: used to validate the telescope performance without crystals on the beam line Transverse position scan: used to find the crystal, when it crosses the beam Crystal angular scan: used to identify the interesting angular regions - amorphous, channeling and volume reflection orientations. High statistic acquisitions: performed in the region where we want fully analyze a given effect. Typically, done in the optimum channeling orientation. R. Rossi - H8 crystal data analysis6 16/05/14 UA9 Crystals Two kind of crystals were test in H8 Strip crystal : the anticlastic bending is induced on the planes (110) Quasi-mosaic crystal : the anticlastic bending is induced on the planes (111) The main difference is that the strip channels have all the same width, while the QM have a main channel and a smaller secondary (1/3). R. Rossi - H8 crystal data analysis7 A total of 15 crystals were analyzed, 10 strip and 5 quasi-mosaic 16/05/14 Run Analysis We developed analysis tools in Root to get from the raw data (details in next slides): Alignment run -> check of beam parameters (e.g. input distributions on crystal) telescope resolution Hi stat CH -> Geometrical cut (different strategy between ST and QM) Torsion correction Crystal channeling efficiency Dechanneling length First look to transition region Angular scan run -> Volume capture features The analysis for the STF45 crystal is shown in the following slides as a case study 8R. Rossi - H8 crystal data analysis 16/05/14 Alignment Run Analysis With the crystal removed from the line is possible to measure the key parameters : Beam divergence Beam distribution Telescope resolution 9R. Rossi - H8 crystal data analysis 16/05/14 Alignment Run Analysis The incoming beam spot can be well approximated by a double Gaussian (see next slide). The surrounding background (square area in light blue) is given by the interaction of the beam particle with the micro collimators placed at the beginning of the line; When the micro collimators are moved the shape of the background change. 10R. Rossi - H8 crystal data analysis 16/05/14 Alignment Run Analysis Here we can see the beam profile in the orthogonal plane. The plots show the double Gaussian shape of the beam core with a sigma of 0.96 mm and 0.72 mm in x and y respectively. The asymmetric tail are not fitted, because are the background due to the micro collimators. 11R. Rossi - H8 crystal data analysis 16/05/14 Alignment Run Analysis The beam divergence is found to be rad in x and 7.66 rad in y. This beam characteristics are crucial for the key measurements. Because the input angular distributions are bigger than c, we need to apply a selection to analyze the different effects. 12R. Rossi - H8 crystal data analysis 16/05/14 Alignment Run Analysis This plot shows the difference between the outgoing and the incoming angle of the tracks without any object on the beam line. The sigma of this distribution gives us the telescope resolution taking into account a variety of systematic effects, including scattering in air. The resolution of the telescope is 5.7 rad in good agreement with the resolution estimated in [1]. 13R. Rossi - H8 crystal data analysis [1] M. Pesaresi et al., Design and performance of a high rate, high angular resolution beam telescope used for crystal channeling studies,2011 JINST 6 P /05/14 Alignment Run Recap Xtal codeYear Beam Profile x [mm] Profile y [mm] diivergence x [rad] Divergence y [rad] resolution [rad] STF38A ,132700,130300,074680, , ,014000, ,670007,658005,61900 STF40A ,241800,142200,152400, , ,017000, ,680007,697005,75600 STF45A ,160200,103700,011500,024430, ,001000, ,650007,684005,76200 STF ,003700, ,269400,039010, ,063000, ,730008,964005,28300 STF ,002050, , ,071460, ,055000, ,880008,982005,30200 STF ,061750,028091, ,073020, ,075000, ,170008,973005,25900 STF , , ,913800,364100, ,294000, ,900008,049005,49400 STF , ,015850,899200,371800, ,290000, ,880008,022005,49600 STF ,051290, ,105000, , ,239000,827409,216005,748005,28400 STF ,047910, ,959000, , ,215000,824609,111005,731005,31100 Xtal codeYear Beam profile x [mm] profile y [mm] divergence x [rad] divergence y [rad] resolution [rad] QMP ,006010, ,932800, , ,269000,820509,134005,774005,42100 QMP ,241800,142200,152400, , ,017000, ,680007,697005,73100 QMP ,350300, ,951000, , ,287000,821709,153005,770005,40800 QMP ,051290, ,105000, , ,239000,827409,216005,748005,28400 QMP ,000840, , ,041660, ,059000, ,830008,949005,28600 Each crystal has a good alignment run If a run is missing, the closer one is used. 14R. Rossi - H8 crystal data analysis 16/05/14 Hi Channeling Two kinds of cuts are performed on the initial distributions: Geometrical cut Angular cut The geometrical cuts are used to select particle impinging on the crystals and can be established by looking at the spread given by the multiple coulomb scattering. The angular cuts are performed to study the coherent interactions in crystals. R. Rossi - H8 crystal data analysis15 16/05/14 Geometrical cut 16R. Rossi - H8 crystal data analysis Cut -> [-0,1;0,2] mm 16/05/14 Cut recap Xtla codeYear Cut x [mm] y [mm] Initial gonio angle [rad] STF38A ,0500-2, ,05002,2933 STF40A2010 STF45A ,1000-2, ,20002,2778 STF ,9000-2,8314 1,10002,8620 STF ,7000-2, ,30002,8910 STF ,1500-2, ,40002,9642 STF ,7000-2, ,30002,5730 STF ,1000-2, ,90002,4583 STF ,5250-2, ,42502,4883 STF ,4000-2, ,60002,4888 Xtla codeYear Cut x [mm] y [mm] Initial gonio angle [rad] QMP ,2500-0, ,45000,0000 QMP ,4000-1,5000 0,00001,5000 QMP QMP , ,50001,5000 QMP R. Rossi - H8 crystal data analysis The table summarize the geometrical cuts made 16/05/14 For particles with the same impact angle, the torque applied to the crystals causes different relative angles with respect to the crystal planes. The difference if proportional to the y impact location. This effect is defined as torsion. As a result, the channeling efficiency varies with both the horizontal impact angle and the vertical impact position. The channeling efficiency is defined as the number of channeled particles normalized to the total number of particles Channeled events are calculated from the deflection profile Torsion Analysis 18R. Rossi - H8 crystal data analysis 16/05/14 Efficiency vs. Impact angle x vs. Impact y 19R. Rossi - H8 crystal data analysis 2-dimensional efficiency plot as a function of impact x angle and impact y points is obtained. The center of gravity of each stripes on the impact y point axis gives the mean impact x angle as a function of vertical impact position 16/05/14 Efficiency vs. Impact angle x vs. Impact y STF48 20R. Rossi - H8 crystal data analysis The linear regression gives the torsion value and the initial impact angle offset 16/05/14 Torsion correction If we define the impact x angle as The torsion correction made is 21R. Rossi - H8 crystal data analysis The plots show the x deflection as a function of the impact x angle before and after the torsion correction 16/05/14 Torsion Recap Xtla codeYear Torsion Initial gonio angle [rad] torsion [rad/mm] angle offset [rad] STF38A ,032-5,515 STF45A ,358-9,920 STF ,5211,753 STF ,9427,285 STF ,3105,285 STF ,998-4,654 STF ,075-2,193 Xtla codeYear Torsion Initial gonio angle [rad] torsion [rad/mm] angle offset [rad] QMP ,8882,217 QMP ,381 -0,351 QMP ,343-0,873 QMP ,634 -2,424 22R. Rossi - H8 crystal data analysis 16/05/14 The calculated torsions are summerized in this table Hi Channeling Analysis The optimum channeling condition is the one studies in more detail. R. Rossi - H8 crystal data analysis23 All the analysis are performed by studying the deflection x angle as a function of the impact x angle. We can then distinguish three regions with respect to the x deflection Channeling, the spot around 150 rad Transition region between the amorphous and the volume reflection zone Dechanneling, the region between the first two 16/05/14 The channeling efficiency is evaluated at two different angular cuts 5 e 10 rad, that for 400 GeV/c protons represent the critical angle for channeling and two times the critical error, respectively. Projecting on the y axis the kick, with the cut described, are obtained. 5 rad 10 rad 24R. Rossi - H8 crystal data analysis Channeling Efficiency 16/05/14 At 5 rad the channeling efficiency is measured to be 0,69. Channeling efficiency recap Xtla codeYear CH Efficiency 5 rad 10 rad STF45A2010 0, , STF , , STF , , STF , , STF , , STF , ,47025 That is the recap of the channeling efficiency for the analyzed crystals 25 Xtla codeYear CH Efficiency 5 rad 10 rad QMP , , QMP , , R. Rossi - H8 crystal data analysis QMP ,5050,405 16/05/14 On the same histogram the dechanneling length analysis is also performed A channeled particle can escape from the channel due with the interaction with the crystal plane, this particles are defined as dechanneled particles. 5 rad 10 rad 26R. Rossi - H8 crystal data analysis Dechanneling length The dechanneling probability is described as an exponential decay as a function of the kick angle: the characteristic dechanneling length is calculated from an exponential fit in the dechanneling region. This is a key parameter to improve simulations. 16/05/14 Dechanneling Length 5 rad The exponential fit gives the dechanneling angle. To get the dechanneling length we have to multiply the parameter by the bending radius of the crystal. Variation on the fit range dont show significant changes of the dech length, that is estimated to be ~ 1,4 mm 27R. Rossi - H8 crystal data analysis 16/05/14 Dechanneling length recap Xtla codeYear Dechanneling Length 5 rad 10 rad STF45A2010 1,4251,250 STF ,5251,414 STF ,1860,177 STF ,5231,369 That is the recap of the dechanneling length 28 Xtla codeYear Dechanneling Length 5 rad 10 rad QMP ,1461,352 QMP ,4170,370 R. Rossi - H8 crystal data analysis 16/05/14 The transition zone describes how the amorphous region is transformed to the volume reflection region after the channeling region The trend plotted would be useful for a confrontation with the crystal simulation routines. 29R. Rossi - H8 crystal data analysis Transition zone 16/05/14 The Population of the three different region are evaluated as a function of the impact incoming angle. 30R. Rossi - H8 crystal data analysis Population 16/05/14 Angular Scan Analysis The angular scan has the same geometrical cuts and torsion correction. The deflection x as a function of the impact x angle is shown R. Rossi - H8 crystal data analysis31 In this case we can see all the volume reflection region, and the halo that have the same trend of the channeling spot is the volume capture region. Non-channeled particles can be channeled due to the interaction with the crystal plane. This particles are defined as captured. 16/05/14 Volume capture analysis We define the region of captured particle as the area within 3 of the trend of the channeled spot R. Rossi - H8 crystal data analysis32 The captured population is plotted as a function of the impact x angle. The rise in the end of reflection region is a well-known behavior. This analysis is performed for the first time, we are looking for a model that describes the trends observed. 16/05/14 Example of QM The crystal face xy is not flat, because of a characteristic additional bending on the QM crystal the kick as a function of the impact position (on a fixed crystal) shows a behavior similar to an angular scan. 33 We have to find a region where this curvature is negligible. R. Rossi - H8 crystal data analysis 16/05/14 Conclusion Achieved goals : A complete analysis of the crystal tested in the H8 line has been done. The results of the present analysis fit the results in literature. Many fine systematic effect were analyzed. A complete list of experimental data and inputs are ready for crystal code developers. Future goals : understanding and development of an analytical model of the various fine effects observed. implementation of the analytical models to improve the crystal simulation routines. R. Rossi - H8 crystal data analysis34 16/05/14 BACKUP R. Rossi - H8 crystal data analysis35 16/05/14 recoData caratteristic dfs/Experiment/UA9/Data-Test_beams 2010 data [/2010_09_16,_H8_re-recodata] reconstruction problem Each variable is in the array thetaIn_x, inside the tracks branch The data was reprocessed because of a bug, but some interesting run is still missing 2011 data [/2011_09_07_recodata4] Optimization problem Each variable in some branch is aa array (100 place), of which only the first spot (0) is the real data (should be reprocessed from CMS) 2012 data [/2012_10_12_H8_protons/Data1] [/2012_10_12_H8_protons/Data2][/TB_22_06_2012_recodata] Tree optimized and performant But run collected in different folder data in [/TB_22_06_2012_recodata] is in a tree 2011 like Issue : several run is missing, so some crystals are unanalyzable 36R. Rossi - H8 crystal data analysis 16/05/14 Xtla codeYear Nominal PropietyAnalyzed run x [mm] y [mm] z [mm] bending [rad] curvature [m] torsion [rad/mm] miscut [rad] AlignmentHiStat CH Angular scan STF38A , ,67< STF40A2010 0, , STF45A2010 0, ,333, STF ,14568,890, STF ~170 0, STF ,5550,8~270 TBD< STF ,76TBD70 STF ,67TBD STF STF Xtla codeYear Nominal PropietyAnalyzed run x [mm] y [mm] z [mm] bending [rad] curvature [m] torsion [rad/mm ] miscut [rad] AlignmentHiStat CH Angular scan QMP ,97350 < QMP , , QMP ~ QMP ~ QMP ,96~ Missing re-recoData 2010 Missing angular scan Missing Hi stat ch Bad Angular Scan Moving backward Bad Angular Scan Moving backward 37R. Rossi - H8 crystal data analysis 16/05/14 Dechanneling Length 10 rad 38R. Rossi - H8 crystal data analysis 16/05/14 R. Rossi - H8 crystal data analysis 16/05/14 R. Rossi - H8 crystal data analysis 16/05/14 Angle Scan Run Analysis Angular scan of the crystal, moving the goniometer on the horizontal plane respect to the beam We obtain both the scan of the angular kick with respect to the impact x angle and the goniometer position From the second one we get three stripes in which each effect is quite evident, and we analyze the peak of AM, CH and VR NB : Thats only a check, befor torsion correction, so we dont know jet what is the impact angle respect the crystallographic plane. So for each stripes all the beam divergence is accepted. 41R. Rossi - H8 crystal data analysis 16/05/14 STF50 x deflection vs. impact angle x Down here is subtracted the initial angle scan of the goniometer 42R. Rossi - H8 crystal data analysis 16/05/14 STF50 x deflection vs. the goniometer position on the horizontal plane. Down here is subtracted the initial angle scan of the goniometer AM CH VR Slice selected for the analysis 43R. Rossi - H8 crystal data analysis 16/05/14 Peak AMAM CHCH VRVR 44R. Rossi - H8 crystal data analysis 16/05/14 Agnle Scan Analysis Recap Xtla codeYear Measurements ch peak [rad] vr peak [rad] am peak [rad] STF38A ,600-13,380-0,952 9,7817,8737,377 STF40A2010 STF45A ,500-13,380-0,184 8,4037,8557,800 STF ,140 9,074 STF ,300-13,3400,000 9,7927,6806,900 STF ,900-8,1850,206 7,6307,8716,008 STF ,800-13,9200,142 8,8647,5217,229 STF ,280-13,0000,466 11,3309,1058,158 STF ,020-13,4500,785 9,5438,1207,074 STF ,590-14,5500,396 11,3207,8837,653 Xtla codeYear Measurements ch peak [rad] vr peak [rad] am peak [rad] QMP ,980-13,190-0,736 15,7508,1647,738 QMP ~110 QMP QMP ,600-13,840-0,164 8,9379,5949,343 QMP ,000 0,281 7,506 6,052 From HiStat CH To do Note VR sigma should be 1,387 rad, which have to be added to the AM spread. 45R. Rossi - H8 crystal data analysis 16/05/14 Hi Stat CH analysis Strip geometrical cut Angular kick as function of x and y impact point is measured The x cut is performed where a deflection appear in x deflection and where a spread due to multiple scattering appear in the y deflection plot. Most of the case the y height of the crystal contains the y dimension of the beam y cut : 3 from the mean of the y beam profile 46R. Rossi - H8 crystal data analysis 16/05/14 QM cut We measure the channeling efficiency (#ch/#tot) versus the impact point on the plane xy note : We get a pixeled map of the xy plane. Each pixel have as dimension the spatial tracker resolution (50/60 m) For each pixel we analize the 1dim histogram of the angular kick inferred to each particle. A gaussian fit is performed around the CH peak The channeling event are measured in two different way, depending on the crystal bending Bending > 90 rad : event counted inside the 3 from the mean of the fit Bending ~ 50 rad : gaussian fit integral (because of the overlapped events in the tail) 47R. Rossi - H8 crystal data analysis 16/05/14 QM cut We get a map of the channeling efficiency in each pixel. Then we chose a zone where the efficiency is higher then 0.5 and with a minimal fluctuation QMP27 x = [-0,4 ; 0,0] y = [-1,5 ; 1,5] 48R. Rossi - H8 crystal data analysis 16/05/14 Torsion correction STF47 49R. Rossi - H8 crystal data analysis 16/05/14 Channeling Efficiency 2.5 rad Efficiency = 0,74 50R. Rossi - H8 crystal data analysis 16/05/14 Channeling Efficiency 5 rad Efficiency = 0,69 51R. Rossi - H8 crystal data analysis 16/05/14 Channeling Efficiency 10 rad Efficiency = 0,53 52R. Rossi - H8 crystal data analysis 16/05/14 x kick vs. impact y position is analyzed to measure the bending variation as a function of the vertical impact position The outgoing x angle vs. impact y position is also analyzed to measure directly the torsion as the variation of the outgoing angle as a function of vertical impact position Geometrical cut is used for both the analysis Hi Stat CH Analysis torsion 53R. Rossi - H8 crystal data analysis 16/05/14 STF45 54R. Rossi - H8 crystal data analysis 16/05/14 55 STF45 As we can see, a very slight variation of bending is present in this crystal R. Rossi - H8 crystal data analysis 16/05/14 56 STF45 This torsion value is comparable to the one obtained with the previous method R. Rossi - H8 crystal data analysis 16/05/14