1 / 14

vdM Scan Results in ALICE

vdM Scan Results in ALICE. ALICE Collaboration. Outline. Raw data extraction, and beam intensity Fitting for the shape using single & double Gaussian Pileup correction Numerical sum method Conclusions. Trigger Setup for vdM Scan. V0C 8 cm < r < 76 cm.

montana-wilkerson
Download Presentation

vdM Scan Results in ALICE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. vdM Scan Results in ALICE ALICE Collaboration

  2. Outline • Raw data extraction, and beam intensity • Fitting for the shape using single & double Gaussian • Pileup correction • Numerical sum method • Conclusions ALICE Trigger Meeting

  3. Trigger Setup for vdM Scan V0C 8 cm < r < 76 cm • Each V0-A and C has 32 scintillators with PMT • V0A & V0C coincidence was used for the scan • Essentially background free (<< 1 Hz) V0A 8 cm < r < 100 cm Interaction point 90 cm (3 nsec) 340 cm (11 nsec) ALICE Trigger Meeting

  4. Extracted Raw Data from DCS DB X(horizontal) Y(vertical) • EXCEL sheets were extracted from ALICE DCS Data Base • Data matching among different tables and selections needed (now all established) • Green lines .. Selected time periods for X and Y scans Acquisition flag (0 or 1) X(horizontal) Y(vertical) ALICE Trigger Meeting

  5. Bunch Intensity • BCT bunchintensity data from LHC after offset corrections • B1 BC=1786 1.741 x 1010 (previously used: 1.91) • B2 BC=892 2.065 x 1010 (previously used: 2.01) • Very stable. Variation during scan time is < 0.02%Effect to Luminosity by intensity variation is < 0.05 %  negligible Fill 1090 Offset corrections: B1: 0.35 x 1010 B2: 0.18 x 1010 x y B2 B1 ALICE Trigger Meeting

  6. Bump Calibration X-scan Y-scan • Offline analysis applied for dedicated bump calibration run and compared to the beam displacement provided by LHC • Xvtx = 0.987 Xdisp and Yvtx =0.991 Ydisp • Estimated overall scale error: 2 m ALICE Trigger Meeting

  7. Single Gaussian Approximation • Luminosity with beams with Gaussian shape in transverse planefor BEAM1and  (x1 , y1) and BEAM2(x2 , y2) • If BEAM1 and BEAM2 are displaced by distances (dx, dy)Fitting the trigger rate R = L where  is cross section of the process the trigger counts  Standard deviation by Gaussian fit result scanx and scanx are Assume B1 and B2 have same size (x, y) ALICE Trigger Meeting

  8. Double Gaussian Approximation • Start: where the shapes of two beams are not distinguishable • Since we did “two Gaussian” fit, relative magnitude α and (1-α) of 2 gaus shapes (primary and secondary) have been obtained where g is normalized Gaussian function • Gaussian integration part is where corresponds to Single Gaussian ALICE Trigger Meeting

  9. Single and Double Gaussian Fits Single Gauss, H scanx1=62.4m scanx2=90.5m scanx=63.3m Single Gauss, V scany1=65.0m scany2=179m scany=68.6m • Dashed line in double Gaussian shows only primary Gaussian • Single Gaussian does not fit at tail, however also double Gaussian as well(asymmetric tail for Y scan) ALICE Trigger Meeting

  10. Pile-up /  Correction •  ~ R / ( f kb ) R: Interaction rate for V0 cross section(Not a V0 count rate) f: Machine frequency kb = 1 (number of BX) • Estimated  during the vdM scan at zero displacement (R~1000) is 0.1 • V0 rate = ( 1–e– ) f kb ~ 0.95R • Correctable (fill by fill or BX by BX) Remark • At high , for example  =1.0, difference goes up to 40% better minimize  for next vDM scan but 0.1 or 0.2 are still manageable kb=1 kb=2 kb=3 ALICE Trigger Meeting

  11. After Pile-up Corrected V0 Rates • Maximum rate increases by 4% • X: 953  992 Hz • Y: 949  969 Hz • Difference in X and Y is not beam intensity (2% effect) Use mean = 980.1 Hz • Standard deviations do not change much scanx1=62.7m scanx2=90.4m scany1=66.9m scany2=162m ALICE Trigger Meeting

  12. Numerical Sum Method normalized shape bunch intensity • Assumption (factorized in x and y) • For x-scan with separation b • The sharpness factor P & QFor Gaussian approx, P=1/(2x) • Sum of rate over b • The top (no displacement) rate • Divide B by A, then obtain the sharpness, luminosity and cross section • To apply for discrete values (in our vdM scan, separation step is constant = 22.42 [m]) A B ALICE Trigger Meeting

  13. Numerical Sum Result • Integral • Sx = 152.17  0.67(stat.) [Hz mm] • Sy = 162.20  0.69(stat.) [Hz mm] • Separation-zero values (top rate) with pile-up corrections • Rx(0,0) = 986.72  10.93(stat.) [Hz] • Ry(0,0) = 975.08  10.87(stat.) [Hz] note: Rx and Ry are different • Sharpness • P = 6.484  0.077(stat.) [/mm] corresponds to Gauss x = 43.50 [m] • Q = 6.011  0.072(stat.) [/mm] y = 46.92 [m] • Luminosity and cross section • L = kb f N1 N2 P Q = ( 1.576  0.027stat ) x 1032 [s-1m-2] • v0 = 62.2  0.1(stat) [mb] (statistical error 0.2 %) where the average top rate 980.90 [Hz] is used ALICE Trigger Meeting

  14. Result and Systematic Uncertainty • Possible uncertainties • Bunch intensity error dominated by DCCT baseline shifts and scale [J.J.Gras & W.Kozanecki] … 5%5% 2. V0 top rate discrepancy for X and Y scan … 2% 3. Separation has 2 m error (known from bump calibration) … 4% • Overall uncertainties of 1. to 3.  ~ 8% (preliminary) • Single and double Gaussian fit results show that the result will stay within systematic uncertainties • Numerical sum method does not have influence of fitting, and also independent from Gaussian approximations: Use this value as central value ALICE v0 = 62.2 [mb]  0.2 % (stat.)  8%(syst.) (preliminary) ALICE Trigger Meeting

More Related