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RLT test Analysis Results

RLT test Analysis Results. W. Xie (RBRC) H. Hiejima (UIUC). #4. #5. #6. #2. #3. #1. Three layers of fast scintilitor (used for T0) was installed during RUN4 p-p with radius: 70cm for 1 st , 100cm for 2 nd , 130cm for 3 rd layers.

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RLT test Analysis Results

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  1. RLT test Analysis Results W. Xie (RBRC) H. Hiejima (UIUC)

  2. #4 #5 #6 #2 #3 #1 • Three layers of fast scintilitor (used for T0) was installed during RUN4 p-p with radius: 70cm for 1st, 100cm for 2nd, 130cm for 3rd layers. • Purpose is to check if the proposed RLT is able to work under the various background. • Timing resolution of the scintilitor is about 100ps, i.e. 2-3cm position resolution. • device is inside east arm Dch acceptance to help distinguish background and real tracks. • Device is numbered as the following RLT test Device in RUN4 p-p

  3. At the beginning of RUN4, one whole week was dedicated to the RLT test. The run number is from 126616-127256. • 4 trigger is used for the test: • MinBias Trigger • Clock Trigger • RLT trigger (can be reconstructed from Clock Trigger) • RLT&MinBias trigger. (can be reconstructed from MinBias trigger) • Both full field and zero field run are recorded • 0-field: 126771, 126772, 126773, 126775, 126776, 126778, 126936, 126937, 126938, 126940, 126941, 126943 • DST and CNT was reconstructed containing NtcpRaw object (Dmitri) • Software for the analysis: • Offline/analysis/RLT Run List, Data Structure and Software

  4. Effect of Magnetic Field on PMT Performance South North • Blue: full field • Red: 0-field • All channels see mip peak. Field have very little effect on the pmt gains except the 1st layer, i.e. the one closest to the beam-pipe (i.e. 70cm) and suffer strongest field. • Little effect on Timing resolution (see the following)

  5. Alignment in Y coordinate • 0-field run is used for the alignment to check the Y position of RLT. • 3 cylinders with radius equal to the R position of 3 layers of slats are constructed in the software. The Z and Y component of its intersection point with Dch tracks are recorded as reference points. • Dch tracks are looped within a event and required to be in concidence with adc(north) and adc(south)<threshold. • One can clear see the Y position of all six RLT slat. • This can be used together with the Z-position matching to reject background in the 0-field run.

  6. z L – z Z position Z Position resolution of SLAT from 0-field run Slat#1 • 2cm position resolution is achieved during the 0-field run which corresponds to the expected 100 ps. • Z position Matching is the only way to reject background during the full-field run

  7. Z Position resolution of SLAT from 0-field run Position resolution become worse in the full field run: 2.5-3.0cm. Result obtained using the fitting curve from 0-field run. It could just because the correlation curve between Z and N/S timing difference is different in the full field run compare to 0-field. Enough for background rejection via Dch track matching

  8. only matching cut in Z position is applied in both 0-field and full-field to distinguish real tracks from background • central-arm field is weak in R-Z plane. The projected z position from Dch tracks and RLT position is require to be 8cm, i.e. 3-4 sigmas to be considered as a match. • There’re 3 outputs from NtcpRaw. • ADC, TDC1, TDC2, where TDC1 and TDC2 are the start-time for ADC gate with 7mV and 8mV threshold, respectively. ADC signal satisfying TDC2 is sent out from FEM and passed to counting house patch-panel where the BLT is formed. • NTC TDC has a timing window of 25 ns. All counting is inside the window Timing cut and Matching cut

  9. Rate for Single Slats • If both south and north PMT has non-zero ADC value after the timing cut, the slat is considerd fired. During RUN4 p-p, RLT trigger is formed by requiring slat#2 S/N coincidence. We did not use the RLT data since it cause bias that need to be understood on the results. The reconstructed trigger rate from MinBias and Clock trigger is 10%-20% lower than logbook over all runs with unknown reason. It can be counted as systematic errors for the analysis. • In the two figs: • top left: rate (Hz) vs. run for slat#1. • top right: ratio of the rate (#2, #3) over the rate(#1). • bottom left: ratio of the rate (#4, #5, #6) over the rate(#1). One can see the reduction of rate as a function of distance and the bias in RLT trigger plot

  10. Rate for Single Slats with Dch tracks • Matching cut is applied to distinguish rate coming from Dch tracks with that from soft particle that can not reach Dch, noise or other background. • The figure shows the fraction of rates that coming from sources other than Dch tracks. One can see Dch tracks contribute less to the rate in clock trigger than in MB trigger • The similarity between 0-field and full-field run shows the major contribution is not from soft particles from collision. It can be albedo, noise or any other sources.

  11. Single slat rate in Clock and MB trigger Left hand side plot shows the ratio of single slat rate in Clock trigger and MB trigger for each slat, respectively. Most of the MB trigger see should be collision related. Clock trigger see both collision and beam-related background. One can see at the beginning of RUN4 p-p, the beam-related background is huge due to the machine performance, then ratio come down and keep at about 2.2. There’s little dependence on the distance from the beam-pipe

  12. Disentangle Beam and Collision Related Background • Assume beam –related background is negligible in MinBias trigger • rate from beam-related background: BBG • rate from Collision-related background including soft particles: CBG • rate from true tracks in PHENIX acceptance: signal Clock trigger events contain: BBG+CBG+signal MinBias trigger events contain: BBG+signal. The result in previous page shows: The results in page10 bottom figure shows the BBG/(BBG+signal) is: • 75% for slat#1, which means: BBG=0.57CBG • 65% for all other slats, which means: BBC=0.66CBG. The result on the right plot shows when there’s central arm tracks, the BBC efficiency is above 60%. We took 65% BBC efficiency since most of the particle seen is low pT one.

  13. Taking into account the absolute rate in MB events at page 9, • the CBG for slat#1 is: 100%(absloute, normalized to slat#1)*75%=75% • the CBG for slat#2,3 is: 70%(absolute, normalized to slat#1)*65%=46% which is 40% lower than slat#1 • the CBG for slat#4,5,6 is: 60%(absolute, normalized to slat#1)*65%=39% which is 48% lower than slat#1. This means the BBG for each slats is: • slat#1: 0.57*75% = 0.43 • slat#2,3: 0.66*46%=0.30 which is 30% lower than slat#1 • slat#4,5,6: 0.66*39%=0.26 which is 40% lower than slat#1 There’s the possibility that the acceptance of BBG and CBG is different. Assuming all BBG is going along Z direction and all CBG is going radially. The width of a slat is about 8cm and thickness is about 2cm. This means the acceptance for BBG is ¼ of CBG and above results is changed correspondingly.

  14. Rate in Two layer Coincidence: 1st and 2nd 4 different type of combination can be formed for two layer coincidence • type#1: (slat#1 is fired by Dch tracks) && (slat#2 || slat#3 is fired by Dch tracks). This is the signal for a two-layer RLT since the RLT is fired by the true tracks. All other types are background that will degrade the accuracy of measurement. • type#2: (slat#1 is fired by Dch tracks) && (both slat#2 and slat#3 are fired by none-Dch tracks) • type#3: slat#1 is fired by none-Dch tracks && (slat#2 || slat#3 is fired by Dch tracks) • type#4: none of slat#1, #2 and #3 is fired by Dch tracks.

  15. Clock trigger • In each figure, the top plot shows the rate (Hz) for each type of combination. The bottom plot shows the ratio of rate (non-type#1)/rate(type#1). • One can see that in MinBias events, the biggest background is type#3, which is about 40% of the signals. In RLT trigger, different type of background increased by about a factor of 2. • This tells the RLT depending on only the two layer, i.e. 1st and 2nd coincidence is not going to work. MinBias

  16. Rate in Two layer Coincidence: 2nd and 3rd Similarly 4 different types of combination can be formed for two layer coincidence • type#1: (slat#2||slat#3 is fired by Dch tracks) && (slat#4 || slat#5||slat#6 is fired by Dch tracks). This is the signal for a two-layer RLT since the RLT is fired by the true tracks. All other types are background that will degrade the accuracy of measurement. • type#2: (slat#2||slat#3 is fired by Dch tracks) && (none of slat#4,#5,#6 is fired by Dch tracks) • type#3: neither slat#2 and #3 is fired by Dch tracks && (slat#4 || slat#5||slat#6 is fired by Dch tracks) • type#4: none of slat#2, #3, #4, #5, #6 is fired by Dch tracks.

  17. In each figure, the top plot shows the rate (Hz) for each type of combination. The bottom plot shows the ratio of rate (non-type#1)/rate(type#1). • One can see that in MinBias events, the biggest background is still type#3 but is much smaller compare the results using 1st and 2nd layer, i.e. a few percent level instead of 40% level. This should owe to the further distance from beam pipe. In RLT trigger, the backround is higher by a factor of 2-3, at the level of 3-4%. • the distance does help reducing the background. MinBias

  18. 8 different types of combination can be formed for three layer coincidence • type#1: slat#1 fired by Dch track && (slat#2||slat#3 is fired by Dch tracks) && (slat#4 || slat#5||slat#6 is fired by Dch tracks). This is the signal for a 3 layer RLT since the RLT is fired by the true tracks. All other types are background that will degrade the accuracy of measurement. • type#2: slat#1 fired by non-Dch track && (slat#2||slat#3 is fired by Dch tracks) && (slat#4 || slat#5||slat#6 is fired by Dch tracks). • type#3: slat#1 fired by non-Dch track && (slat#2||slat#3 is fired by Dch tracks) && (none of slat#4,#5,#6 is fired by Dch tracks) • type#4: slat#1 fired by non-Dch track && (neither slat#2 and #3 is fired by Dch tracks) && (slat#4 || slat#5||slat#6 is fired by Dch tracks) • type#5: none of slat#1, #2, #3, #4, #5, #6 is fired by Dch tracks. • type#6: slat#1 fired by Dch track &&(slat#2||slat#3 is fired by Dch tracks)&& (none of slat#4,#5,#6 is fired by Dch tracks) • type#7: slat#1 fired by Dch track &&(neither slat#2 and slat#3 is fired by Dch tracks)&& (slat#4 || slat#5||slat#6 is fired by Dch tracks) • type#8: slat#1 fired by Dch track &&(neither slat#2 and slat#3 is fired by Dch tracks)&& (none of slat#4,#5,#6 is fired by Dch tracks) Rate in three layer Coincidence

  19. In each figure, the top plot shows the rate (Hz) for each type of combination. The bottom plot shows the ratio of rate (non-type#1)/rate(type#1). • One can see the background rate become worse than the 2 layer coincidence from 2nd and 3rd layer. This is not a surprise since the type#2 and type#6 which is considered as background here is the signal for the two layer coincidence between 2nd and 3rd.

  20. Shows the same result as previous page but for type#6 to #8. • One can conclude that a simple RLT relying on 3 layer detector coincidence will not work. Different ways might help reduce the background. One is through a LUT that cover only region that correlated the real tracks or/and move the 1st layer to larger radius.

  21. Back up Slide

  22. 0-field run position resolution for all other 5 slats

  23. 0-field run position resolution for all other 5 slats

  24. One possible to check the beam related background is to check the slat rate in the non-collision bunches. The rate measured in wrong bunches should produce information on beam related background if a significant amount of beam leaked into the wrong bunches. The left figure show the rate of slat#1 for clock and MB trigger. One can see little contribution from wrong bunches. This mean there’s little leak from correct bunches to the wrong bunches.

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