ATO-98 - connect distortion trees - with custom description ()
[u/mrichter/AliRoot.git] / TPC / doc / Definitions / .nfs000000002088d37300000196
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a55b333f 1÷\ 2\ 1ƒ’À\1c;\0\0\0\0\ 3è\e TeX output 2011.03.13:1821‹\0\0\0\ 1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0ÿÿÿÿ \ 2–\0\0 ýv\0\0 \ 2l\0\0 þ ë\ fŸ”jE’\0¤Ínó\ eX«Q\v\0\f\0\0\0\f\0\0\0\ 5cmr12¹ALICE–\ 3ê¨In¬rternal“NoteŽŸ\ e€\0’\0Ÿ–(ALICE-INT-2011-XXXŽŸ>ÿð‘({6ó\ fDÓít\0\14½q\0\11\0\ 5cmr17ºDe\fnitions–\ 6BÚof“TPC“related“trac‘ÿuNk“prop‘\0Š±ertiesŽŸ#ŸôŸ\1a?ø’\0¬<{ó\10X«Q\v\0\ eff\0\f\0\0\0\ 5cmr12»Marc›¼h–\ 4³/13,“2011ŽŸ,9Ž’\0ÈÂó\1c\1aò"V\0
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3\0\0\0\ 6cmbx10ÇAbstractŽŸ\14Mƍ‘Al¯ó\eKñ`y\0
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5\0\0\0\ 5cmr10ÆThis–\ 4C®došMÞcumen²!t“is‘\ 4C¯supp˜osed“to“help“users“in“the‘\ 4C¯analysis“of“ALICEŽŸ\r™š‘0ÿàTPC‘\ 3¦fdata.ŽŽŽ \0ŒªŒ‘\ 2\0\0ó/ÂÖN \0\11\0\f\0\0\0\ 6cmbx12Ú1Ž‘\1f(ôDe\fnitionsŽŸ\1dâ#‘\ 2\0\0ó0ÂÖN \0\ eff\0\f\0\0\0\ 6cmbx12Û1.1Ž‘&æcClustersŽŸ\16@\0‘\ 2\0\0ó1ÂÖN \0\f\0\0\0\f\0\0\0\ 6cmbx12ÜTPC‘\ 4€\0cluster.ŽŽ‘Sü\13¹A‘\ 3›úc•¬rharged›\ 3œ\ eparticle‘\ 3œ\rtra“v“ersing˜the˜TPC‘\ 3›úinduces‘\ 3œ\ra˜signal˜on˜a˜giv“en‘\ 3œ\rpad-ro“w.‘\ 5\1e­IfŽ¤\ e€\0‘\1f_ìthe–\ 4~^c¬rharge›\ 4~_in“a˜searcš¬rh“windo˜w›\ 4~_of“5˜pads“in˜wire“direction˜and“5˜bins“in˜time“directionŽ¡‘\1f_ìexceeds–\ 3…Ca“certain“threshold“and“ful\flls“all“necessary“qualit¬ry“criteria,‘\ 3™‹it“is“called“a“cluster.Ž¡‘\1f_ìTherefore–\ 4Âõthe“maximš¬rum“n˜um˜bšSŽer“of“clusters“p˜er‘\ 4Âötracš¬rk“is“159“whic˜h“correspSŽonds“to“theŽ¡‘\1f_ìn•¬rum“bSŽer–\ 4û\10of›\ 4û\ fpad“ro¬rws“in˜a“giv¬ren“TPC‘\ 4úÉsector.‘\bj\18Curling˜trac¬rk“parts“are˜reconstructed“asŽ¡‘\1f_ìseparate‘\ 3ê¨trac¬rks.ŽŸ\18†Æ‘\1f_ìó2›»ˆ@\0\f\0\0\0\f\0\0\0\ 6cmti12ÝNumb‘ÿffer–\ 435of“TPC“clusters:‘\ 58àó\1f·ág£\0\f\0\0\0\f\0\0\0\ 6cmmi12ÊnŸ\ 1ÌÌó ×\ 1\172\0\b\0\0\0\b\0\0\0\ 5cmmi8ËclŽ‘
6ºé¹/‘\ 3ê¨ó3߆µT\0\f\0\0\0\f\0\0\0\ 6cmtt12ÞAliESDtrack::GetTPCNcls()ŽŸ\18†Ç‘\1f_ì¹The›\ 3SŠn•¬rum“bSŽer˜of–\ 3S‰clusters˜assigned˜to˜a“trac¬rk˜is˜related˜to“the˜trac¬rk˜length˜in“the˜sense˜thatŽ¡‘\1f_ìlo•¬rw›\ 47IÊpŸ\ 1ÌÌËtŽ‘\ 3‘ʹ-trac“ks‘\ 47Hwhic“h˜do‘\ 47Hnot˜reac“h–\ 47Hthe˜outer“w¬rall˜of“the˜TPC‘\ 474ha•¬rv“e˜less‘\ 47Hclusters˜assigned.Ž¡‘\1f_ìHo•¬rw“ev“er,‘\ 69the–\ 5Ãarelation“is›\ 5Ãbnot“straigh•¬rtforw“ard,‘\ 69bSŽecause˜the–\ 5Ãapad“length˜in“the“TPC‘\ 5ÂèisŽ¡‘\1f_ìincreasing–\ 3ê¨with“radial“distance“to“the“cen¬rter.ŽŸM/iŸä€\0Ÿñ€\0‘\ 2\0\0Figure–\ 4²Ã1:‘\ 6É\15\ 4²c¬rharged“particle›\ 4²Âin“one“TPC‘\ 4²sector.‘\a‘1In“this˜case,‘\ 4äÊthe“trac¬rk“crosses˜all“159“padŽ¡‘\ 2\0\0roš¬rws–\ 3ê¨(63“in“the“inner“read-out“c˜ham˜bSŽer“and“96“in“the“outer“read-out“c˜ham˜bSŽer).ŽŽŽ¡ŽŸ\1d‹L‘\ 2\0\0ÜFindable‘\ 4€\0clusters.ŽŽ‘p(+¹The›\ 4\1e\an•¬rum“bSŽer–\ 4\1e\ 6of˜\fndable˜clusters˜is“the˜n•¬rum“b•SŽer˜of‘\ 4\1e\ 6geometrically˜p“ossibleŽ¡‘\1f_ìclusters–\ 5§Lwhicš¬rh“can“bSŽe“assigned“to“a“trac˜k.‘
7nËIt“tak˜es“in˜to“accoun˜t“dead“zones“due“toŽŽŸ\1e\0\0’\0ï\10\ 21ŽŽŒ‹\0\0\0\ 2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\ 2–\0\0 ýv\0\0 \ 2l\0\0 ý¹\0\0‘\1f_ì¹c•¬rham“b•SŽer›\ 4‹Èb“oundaries–\ 4‹Çor˜the“limited˜Ê\11n9¹-acceptance.‘\a\1c>F‘ÿ\ 5Vor˜the“time˜bSŽeing,‘\ 4´\ fclusters“on˜deadŽ¤\ e€\0‘\1f_ìfronš¬rt-end–\ 3ê¨cards“are“coun˜ted“as“\fndable.ŽŸ\19€\0‘\1f_ìÝNumb‘ÿffer–\ 435of“\fndable“TPC“clusters:‘\ 58àÊnŸ\ 1ÌÌËf‘\0áÇindŽ‘\15Ι¹/‘\ 3ê¨ÞAliESDtrack::GetTPCNclsF()ŽŸ\1e€\0‘\ 2\0\0ÜNon-\fndable‘\ 4€\0clusters.ŽŽ’\0ˆ¹ó¹If–\ 3¼2a“trac¬rk“crosses“the“bšSŽoundary“b˜et•¬rw“een›\ 3¼2t“w“o˜c“ham“bSŽers˜or˜lea“v“es˜theŽ¡‘\1f_ìÊ\11n9¹-acceptance,–\ 3ê¨the“clusters“in“this“area“are“declared“as“non-\fnable.Ž©\18€\0‘\ 2\0\0ÜMissing–\ 4€\0cluster“/“cluster“b`\0elo \0w“threshold.ŽŽ’\0þ<s¹Findable–\ 2œpclusters“can“bšSŽe“missing,‘\ 2ßHb˜ecause“theirŽ¡‘\1f_ìc•¬rharge›\ 4¹ïis‘\ 4¹ðbSŽelo“w˜threshold˜(e.g.‘\a¦¶due–\ 4¹ðto˜baseline˜shifts“etc.).‘\a¦¶They˜can˜bSŽe“iden•¬rti\fed˜b“yŽ¡‘\1f_ìloSŽoking–\ 4“´inš¬rto“the“neigh˜bSŽoring“pad-ro˜ws,‘\ 4½÷e.g.‘\a4\ 3if“there“is“no“reconstructed“cluster“on“padŽ¡‘\1f_ìro¬rw–\ 3EÑÊi¹,‘\ 3fÉbut›\ 3EÒclusters“are“found“on˜the“pad“ro¬rws˜Êi–\ 1Y÷ó"!",š\0\f\0\0\0
8\0\0\0\ 6cmsy10Í\0“¹1‘\ 3EÑand˜Êi“¹+“1‘\ 3EÑ(or˜Êi“Í\0“Êr›\ 3™`¹and‘\ 3EÑÊi“¹+“Êr˜¹in‘\ 3EÑgeneral).Ž¡‘\1f_ìThe›\ 3ê¨n•¬rum“b•SŽer˜of˜clusters˜b“elo¬rw˜threshold˜is˜called˜ÊnŸ\ 1ÌÌËmissŽ‘\12Æ\16¹.Ž¦‘\ 2\0\0ÜNumš \0b`\0er–\ 4€\0of“crossed“ro˜ws“ÊnŸ\ 1ÌÌËef‘\0áÇfŽ‘\ e_®Ü.ŽŽ’\0³ç|¹The›\ 3Ûhrelev‘ÿXäan•¬rt‘\ 3Ûiquan“tit“y˜for–\ 3Ûithe˜ÊpŸ\ 1ÌÌËtŽ‘\ 3‘ʹ-resolution“of˜a“trac¬rk˜is“theŽ¡‘\1f_ìe\vectiv•¬rely›\ 4Xósampled‘\ 4Xòtrac“k˜length˜of–\ 4Xòa˜particle˜in˜the“TPC,˜bSŽecause˜the“resolution˜scalesŽ¡‘\1f_ìroughly–\ 3i\ fÍ/ŸûFu‘\v©7ó\1d|{Y\a\0\b\0\0\0\b\0\0\0\ 4cmr8È1Ž‘\ 4ˆ…Ÿ\ 1öû‰\0\0\0\12hŸ\ 6åꍍŸúð7ó#¾KÈ\v\0\b\0\0\0\b\0\0\0\ 5cmsy8ÎpŽ‘\a\15\Ÿúð7‰\0\0\)\0\vl\fŸ\ 5\ fɍËnŸ\ 1i?ó!\10;Î\0\ 6\0\0\0\ 6\0\0\0\ 5cmmi6ÌclŽŽŽŽŽŽŽ‘\e¦.¹(statistics)“and–\ 3i\ eÍ/›\ 3URÊnŸû¥2È2ŽŸ\ay¹Ëef‘\0áÇfŽŽ‘\11Ƚ¹(lev¬rer“arm)‘\ 3i\ fwhere“ÊnŸ\ 1ÌÌËef‘\0áÇfŽ‘\11µ\0¹=˜ÊnŸ\ 1ÌÌËclŽ‘\br3¹+‘\ 1¡òÊnŸ\ 1ÌÌËmissŽ‘\12Æ\16¹.‘\ 5\r¬The‘\ 3i\ fn•¬rum“bSŽerŽŸ\10\f¼‘\1f_ìis–\ 3ê¨a¬rv‘ÿXäailable“via“the“ÝA³2liR–ÿffo“ot¹-F‘ÿ\ 5Vunction:Ž¤\19€\0‘\1f_ìÝNumb›ÿffer–\ 435of“cr˜osse˜d“r˜ows:‘\ 58àÊnŸ\ 1ÌÌËef‘\0áÇfŽ‘\12JV¹/‘\ 3ê¨ÞAliESDtrack::GetTPCClusterInfo(r–\ 6,Í=“2,1)¹.Ž¡‘\1f_ìIn–\ 4.Àthis“particular“case“(Êr‘\ 4\1cȹ=‘\ 3É92),‘\ 4?Æa“missing“cluster“is‘\ 4.Áassigned“if“a“cluster“is“found“on“oneŽ¤\ e€\0‘\1f_ìof›\ 4±Àthe‘\ 4±Át•¬rw“o˜neigh“bSŽoring›\ 4±Ápad-ro“ws.‘\aŽ)The˜n“um“bSŽer–\ 4±Àof“crossed˜ro¬rws“ÊnŸ\ 1ÌÌËef‘\0áÇfŽ‘\13\11o¹can“also˜bSŽe“calledŽ¡‘\1f_ìe\vectiv•¬re›\ 3qhcluster‘\ 3qgtrac“k˜length.‘\ 5\10uW‘ÿ\ 5Ve˜can˜consider‘\ 3qgthe˜follo“wing˜example:‘\ 4ü@Imagine‘\ 3qga˜c“hargedŽ¡‘\1f_ìparticle–\ 3ß\aenš¬rters“the“TPC‘\ 3ß\ 4at“the‘\ 3ß\ 6inner“w˜all“with“a“ÊpŸ\ 1ÌÌËtŽ‘\apѹin“suc˜h“a“w˜a˜y‘\ 3ß\ 6that“it“w˜ould“cross“allŽ¡‘\1f_ìpad–\ 3ðÕcro¬rws›\ 3ðÖin“an˜activ¬re“area,‘\ 3òabut˜it“undergoSŽes˜a“catastrophic˜hadronic“in¬rteraction˜in“theŽ¡‘\1f_ìmiddle–\ 3å4of“the“TPC,‘\ 3å3then“ÊnŸ\ 1ÌÌËf‘\0áÇindŽ‘\159C¹=›\ 3UR159,‘\ 3æKbut“ÊnŸ\ 1ÌÌËef‘\0áÇfŽ‘\11µ\0¹=˜80“and“(if“e.g.‘\ 57\ f3%‘\ 3å3of“the“clusters“w¬rereŽ¡‘\1f_ìbSŽelo¬rw–\ 3ê¨threshold)“ÊnŸ\ 1ÌÌËclŽ‘
9%“¹=‘\ 3UR76.Ž¦‘\ 2\0\0ÜNum \0b`\0er–\ 4€\0of“clusters“after“\frst“iteration.ŽŽ’\0ïý)¹If–\ 3Xßa›\ 3Xàtrac¬rk“is˜recognized“as“a˜kink“candidate,‘\ 3v\bit“isŽ¡‘\1f_ìsplit–\ 3]_inš¬rto“a‘\ 3]^mother“and“a“daugh˜ter“trac˜k.‘\ 5 ÇHo˜w˜ev˜er,‘\ 3y¡the“n˜um˜bSŽer“of“assigned‘\ 3]^clusters“ÊnŸ\ 1ÌÌËclŽ‘
10- ¹isŽ¡‘\1f_ìthe–\ 3Zfsum›\ 3Zgof“the“clusters“assigned˜to“the“mother˜and“the“daughš¬rter.‘\ 5\bÊThe“n˜um˜bSŽer‘\ 3Zgof“clustersŽ¡‘\1f_ìassigned–\ 39 to›\ 39\1fthe“mother“trac¬rk“are˜still“a¬rv‘ÿXäailable“via˜the“n•¬rum“bSŽer–\ 39 of“clusters˜assigned“duringŽ¡‘\1f_ìthe–\ 3ê¨\frst“(in•¬rw“ard)›\ 3ê¨trac“king˜iteration.ŽŸ\19€\0‘\1f_ìÝNumb›ÿffer–\ 435of“clusters“after“\frst“iter˜ation:‘\ 58àÊnŸ\ 1ÌÌËcl\18K;iter<rÈ1Ž‘\1fQ×¹/‘\ 3ê¨ÞAliESDtrack::GetTPCNclsIter1()¹.ŽŸ(Ê«‘\ 2\0\0Û1.2Ž‘&æcT‘þ¦fracŒÌk‘\ 5ffparametersŽŸ\16@\0‘\ 2\0\0¹There–\ 3µhare“t•¬rw“o‘\ 3µgt“ypSŽes–\ 3µhof“relev‘ÿXäanš¬rt“trac˜k›\ 3µgparameters“for“a“TPC‘\ 3µZbased“data˜analysis:‘\ 5\1e@Ýglob‘ÿffal“¹(trac¬rkŽ¡‘\ 2\0\0parameters–\ 3ê¨are“upSŽdated“with“inner“detectors,“i.e.‘\ 58àthe“ITS)“and“ÝTPC–\ 435stand-alone“(TPC-SA)¹.ŽŽŸ\1e\0\0’\0ï\10\ 22ŽŽŒ‹\0\0\0\ 3\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\ 2–\0\0 ýv\0\0 \ 2l\0\0 ý¹\0\0‘\ 2\0\0ÜTPC-SA–\ 4€\0tracš \0k“parameters“at“the“primary“v˜ertex.ŽŽ’\ 1+ó1¹They–\ 5\16ôdescribšSŽe‘\ 5\16õthe“trac¬rk“prop˜ertiesŽ¤\ e€\0‘\1f_ìat–\ 4õthe“primary“vš¬rertex“as“obtained“with‘\ 4öthe“TPC‘\ 4Ëstand-alone.‘\a"ÇThese“trac˜k“parametersŽ¡‘\1f_ìare–\ 3uwlast“upSŽdated“at›\ 3uvthe“inner“w¬rall“of“the“TPC‘\ 3uYand“then˜propagated“through“the“materialŽ¡‘\1f_ìof–\ 3ê¨the“inner“detectors“to“the“v¬rertex.Ž©\19€\0‘\1f_ìÞAliESDtrack::GetTPCInnerParam()¹.ŽŸ\1e€\0‘\ 2\0\0ÜGlobal–\ 4€\0tracš \0k“parameters“at“the“inner“TPC“w˜all.ŽŽ’\ 1"ÝÚ¹They–\ 3Ì®describSŽe›\ 3̯the“trac¬rk˜propSŽerties“atŽ¡‘\1f_ìthe–\ 3ÂMinner›\ 3ÂNw¬rall“of“the“TPC‘\ 3ÂDas“obtained“with“the˜global“trac•¬rking.‘\ 5+lThese˜trac“k‘\ 3ÂMparametersŽ¡‘\1f_ìm¬rust–\ 4Ö¯bSŽe›\ 4Ö®used“for“the“particles˜iden¬rti\fcation,‘\ 5\11±bSŽecause“the˜energy“loss“of“a˜trac¬rk“insideŽ¡‘\1f_ìthe–\ 3¿TPC‘\ 3¶is“a“function›\ 3ÂÀof“the“total˜momen¬rtum“ÊpŸ\ 1ÌÌËtot;T–\ 1.:P“CŽ‘$1\ 2¹inside˜the“TPC.“The˜global“trac¬rkŽ¡‘\1f_ìparameters–\ 4Nµat›\ 4N´the“inner˜TPC‘\ 4N›w¬rall“are˜a“go•SŽo“d–\ 4Nµ-˜though“not˜pSŽerfect“-˜appro¬rximation“forŽ¡‘\1f_ìthis,–\ 3ê¨bSŽecause“the“energy“loss“inside“the“TPC“\fll“gas“is“rather“small.‘\ 58àŸû¥2È1ŽŽŽ¦‘\1f_ìÞAliESDtrack::GetInnerParam()¹.ŽŸ\1e€\0‘\ 2\0\0ÜGlobal–\ 4€\0tracš \0k“parameters“at“the“primary“v˜ertex.ŽŽ’\ 1 Qj¹These–\ 4\büare›\ 4\bûthe“standard˜parameters“ofŽ¡‘\1f_ìthe–\ 3ê¨ESD“tracš¬rk“and“used“in“the“ma‘\0§\1cjorit˜y“of“the“ph˜ysics“analyses.Ž©\18€\0‘\ 2\0\0ÜGlobal–\ 4€\0tracš \0k“parameters“at“the“outer“TPC“w˜all.ŽŽ’\ 1#Ú¹They–\ 4[íare“only‘\ 4[îstored“in“the“AliESD-Ž¡‘\1f_ìfriends–\ 3ê¨and“are“usually“not“relev‘ÿXäanš¬rt“for“ph˜ysics“analysis.ŽŸ"Ê«‘\ 2\0\0Û1.3Ž‘&æcPID–\ 5ffrelated“quanŒÌtitiesŽŸ\16@\0‘\ 2\0\0ÜEnergy–\ 4€\0loss“ÊdE‘\0´\17=dxÜ.ŽŽ‘uÙV¹A‘\ 2äÔcš¬rharged–\ 2å\16particle“tra˜v˜ersing“the“TPC‘\ 2äÓ\fll‘\ 2å\17gas“is“losing“energy“mainly“viaŽ¡‘\1f_ìionization–\ 3aªprošSŽcesses.‘\ 5\v6The“mean‘\ 3a«energy“loss“ÊdE‘\0´\17=dx“¹p˜er“unit“path‘\ 3a«length“can“b˜e“describ˜edŽ¡‘\1f_ìwith–\ 3ê¨the“Bethe-BloSŽcš¬rh“form˜ulaŽŸ\13€\0Ÿ\12 Ü’\0…ÅÈÍhŸ÷áō‘\ 133ÊdEŽ‘\ 133Ÿ\ 5[«‰\0\0\0\ f¾Ÿ
11ý΍‘\ 1\µdxŽŽŽŽ‘\11è$Íi‘\ 3UR¹=Ÿ÷áō‘\ 4ˆ…4Ê\19n9N‘\ 1@äeŸû¥2È4ŽŽ‘\ 4ˆ…Ÿ\ 5[«‰\0\0\0!Ô:Ÿ
12ý΍‘\ 6ßIÊmcŸüˆ‰È2ŽŽŽŽŽŸ÷áō‘(Ã%ÊZ‘\0ܞŸû¥2È2ŽŽ‘(Ã%Ÿ\ 5[«‰\0\0\0\r§vŸ
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14\0\0\0\ 6cmex10Ð\10ŽŽŽ‘>Èz¹lnŽŸ÷áō‘KÆO2ÊmcŸû¥2È2Ž‘\ 4À\ 4Ê\f‘\0ªOŸû¥2È2Ž‘\ 5jSÊ\r‘\0§\1cŸû¥2È2ŽŽ‘KÆOŸ\ 5[«‰\0\0\01qŸ
15ý΍‘\15°£ÊIŽŽŽŽ’\0%›Í\0‘\ 2ª¨Ê\f‘\0ªOŸû\v™È2Ž‘\b\14ûÍ\0Ÿ÷áō‘\ 3ÝÛÊ\ es2¹(Ê\f‘\0ªO¹)Ž‘\ 3Ý۟\ 5[«‰\0\0\0\16\17
16ý΍‘\b\eµ2ŽŽŽŽ‘\e(tŸò®\rÐ\11ŽŽŽ‘%¨rÊ:Ž’\ 1Òü|¹(1)ŽŽŽŸ\1fe捍‘\ 2\0\0ÜEnergy‘\ 4€\0dep`\0osit.ŽŽ‘d¤÷¹If–\ 4œ:the“energy›\ 4œ9transfer“to“the“ionized“electron˜exceeds“a“certain“v‘ÿXäalue,‘\ 4ȞtheŽ¡‘\1f_ìrange–\ 4\ 4'of“the‘\ 4\ 4(ionized“electron“bšSŽecomes“so“large,‘\ 4
17ˆthat“it“escap˜es“from“the‘\ 4\ 4(sampling“of“theŽ¡‘\1f_ìc¬rharge–\ 4}xsignal›\ 4}wof“a˜givš¬ren“trac˜k.‘\ 6ñNIn“addition›\ 4}wto“this,‘\ 4¢+some˜of“the˜energy“loss˜also“resultsŽ¡‘\1f_ìonly–\ 5 \1cin›\ 5 \1dexcitation“of˜the“\fll“gas˜atoms“and“no˜electrons“are˜released.‘\b”=The“detectableŽ¡‘\1f_ìdepSŽosited–\ 4ýƒenergy›\ 4ý„of“a“trac¬rk“in˜a“givš¬ren“pad-ro˜w‘\ 4ý„is“therefore“sligh˜tly“di\veren˜t‘\ 4ý„from“theŽ¡‘\1f_ìenergy–\ 3ê¨loss“of“the“c¬rharged“particle.Ž¦‘\ 2\0\0ÜMaximš \0um–\ 4€\0cluster“c˜harge“ÊQŸ\ 1ÌÌËmaxŽ‘\11QzÜ.ŽŽ’\0½:\1f¹The–\ 6\ 1¡maximš¬rum‘\ 6\ 1 cluster“c˜harge‘\ 6\ 1 represen˜ts“the‘\ 6\ 1 maxim˜umŽ¡‘\1f_ìv‘ÿXäalue–\ 3ê¨of“all“digits“in“a“cluster“as“sho¬rwn“in“\fgure“1.Ž‘\ 2\0\0Ÿ
18ˆ‡‰\0\0ff\0¿ÿ@Ÿ\v\0\0‘\rƒŸü^ÿó\ 6ٓ R\0\a\0\0\0\a\0\0\0\ 4cmr7±1ŽŽŽ‘\12\0\ 3ó\aKñ`y\0
19\0\0\0
20\0\0\0\ 5cmr10²N.B.:‘\ 4qÇThe–\ 3UUTPC-SA“tracš¸ãk“parameters“at“the“primary“v˜ertex“should“nev˜er“bG\1de“used“for“pid!ŽŽŸ\1e\0\0’\0ï\10\ 2¹3ŽŽŒ‹\0\0\0\ 4\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\18\ 2–\0\0 ýv\0\0 \ 2l\0\0 ý¹\0\0‘\ 2\0\0ÜT‘þà\0otal–\ 4€\0cluster“c \0harge“ÊQŸ\ 1ÌÌËtotŽ‘
21¿TÜ.ŽŽ’\0™]L¹The–\ 5, total›\ 5,Ÿcluster“c¬rharge“is˜givš¬ren“b˜y“the“sum›\ 5,Ÿof“all“digits˜in“aŽ¤\ e€\0‘\1f_ìcluster.‘\ 58àIt–\ 3ê¨correspšSŽonds“to“the“energy“dep˜osit“of“a“tracš¬rk“on“a“giv˜en“pad-ro˜w.ŽŸ\17Ç퍍‘\ 2\0\0ÜTPC–\ 4€\0dE/dx“signal“ÊS‘\0²×Ü.ŽŽ’\0„ÈÛ¹Because–\ 3¨9of“the“long“tail“to•¬rw“ards‘\ 3¨:higher–\ 3¨9energy“losses“in“the“distribu-Ž¡‘\1f_ìtion–\ 4‚@function›\ 4‚?of“the˜cluster“cš¬rharge,‘\ 4¨%the“a˜v˜erage“energy›\ 4‚?depSŽosit“is˜not“a˜go•SŽo“d‘\ 4‚@estimatorŽ¡‘\1f_ìas–\ 4•£it›\ 4•¤w¬rould“bSŽe“for“a˜Gaussian“distribution.‘\a9ÒTherefore,‘\ 4Àbthe“so-called“truncated˜mean“isŽ¡‘\1f_ìused.‘\ 6à÷The›\ 4x\ 4truncated–\ 4x\ 5mean“ÊS‘\ 5*ܹof“all“cluster˜c¬rharges,‘\ 4›\also“called“the“ÝTPC‘\ 4µ\ 3ÊdE‘\0´\17=dx‘\ 4µ%Ýsignal¹,Ž¡‘\1f_ìis–\ 4cÂde\fned“as“the“a•¬rv“erage‘\ 4cÃo“v“er›\ 4cÂlo“w“est˜v‘ÿXäalues,‘\ 4‚\bwhic“h˜correspSŽond‘\ 4cÃto˜a˜60%-fraction˜of˜theŽ¡‘\1f_ìwhole–\ 3ê¨sample.‘\ 58àThe“v‘ÿXäalues“of“ÊS‘\ 4\7f¹follo¬rw“an“almost“pSŽerfect“Gaussian“distribution.ŽŸ\18k䍑\1f_ìÝTPC–\ 435dE/dx“signal“ÊS‘\ 4\7f¹/‘\ 3ê¨ÞAliESDtrack::GetTPCSignal()¹.ŽŸ\1d\ fڍ‘\ 2\0\0ÜNum \0b`\0er–\ 4€\0of“clusters“used“for“PID“ÊnŸ\ 1ÌÌËpidŽ‘\f\vßÜ.ŽŽ’\0åUu¹Clusters–\ 3\14èwhic¬rh›\ 3\14çare“loSŽcated˜v¬rery“close“to˜the“c¬rham-Ž¡‘\1f_ìb•SŽer›\ 4kUb“oundaries–\ 4kTor“from˜o•¬rv“erlapping‘\ 4kTtrac“ks˜are–\ 4kTnot˜used“for˜the“calculation˜of“the˜TPCŽ¡‘\1f_ìdE/dx–\ 4z½signal.‘\ 6é Therefore›\ 4z¾the“n•¬rum“bSŽer–\ 4z½of˜clusters“used“for˜the“calculation“of˜the“dE/dx-Ž¡‘\1f_ìsignal–\ 3¡îcan›\ 3¡íbSŽe“di\veren¬rt“from“the˜n•¬rum“bSŽer–\ 3¡îof“clusters“of˜a“tracš¬rk.‘\ 5 ¢This“quan˜tit˜y“is‘\ 3¡íof“impSŽor-Ž¡‘\1f_ìtan¬rt–\ 3ê¨relev‘ÿXäance“for“the“dE/dx-resolution.ŽŸ\13#ö‘\1f_ìÝNumb›ÿffer–\ 435of“clusters“use˜d“for“pid:‘\ 58àÊnŸ\ 1ÌÌËpidŽ‘\ fö‡¹/‘\ 3ê¨ÞAliESDtrack::GetTPCsignalN()¹.ŽŸ'¶<‘\ 2\0\0Ú2Ž‘\1f(ôRecommendation–\ 6záfor“TPC“Cluster“SelectionŽŸ\1ab#‘\ 2\0\0¹One–\ 3ŒBof›\ 3ŒCthe“ma‘\0§\1cjor˜systematic“error“in˜the“ph¬rysics˜analysis“is“in•¬rtroSŽduced˜b“y–\ 3ŒBselection˜criteria“onŽ¡‘\ 2\0\0the›\ 3?\11n•¬rum“b•SŽer˜of˜clusters.‘\ 4ÿ®Based˜on‘\ 3?\12exp“erience˜with˜TPC‘\ 3>ådata‘\ 3?\12of˜2009˜and˜2010,‘\ 3acit˜is˜kno¬rwn˜thatŽ¡‘\ 2\0\0TPC‘\ 44[gain–\ 44mand›\ 44nbaseline“v‘ÿXäariation˜in\ruence“the˜distribution˜of“found˜clusters“up˜to“30%˜lev¬rel.Ž¡‘\ 2\0\0This–\ 4~{v‘ÿXäariation›\ 4~|is“time,‘\ 4£qenergy“loss,‘\ 4£pand˜running“condition˜depSŽenden¬rt“and˜it“is˜only“partiallyŽ¡‘\ 2\0\0describSŽed–\ 4„¸in“the›\ 4„¹MC.“Ho•¬rw“ev“er,‘\ 4«<this–\ 4„¸v‘ÿXäariation˜in\ruences“the“TPC‘\ 4„‘trac¬rking“pSŽerformance“onlyŽ¡‘\ 2\0\0to–\ 3ê¨the“lev¬rel“of“ŸõêïÐpŽ‘\ fꪟõêï‰\0\0\0M\e¸Ÿ
22\15\11¹1–\ 2ª¨Í\0“ÊnŸ\ 1ÌÌËmissŽ‘\12Æ\16Ê=nŸ\ 1ÌÌËf‘\0áÇindŽŽŽŽ‘]\ 6b¹.Ž¡‘\13ŸôMost–\ 3U;analyses“cut›\ 3U:on“the“n•¬rum“bSŽer–\ 3U;of“found˜TPC‘\ 3U\15Clusters“divided“b¬ry“the˜n•¬rum“bSŽer–\ 3U;of“\fndableŽ¡‘\ 2\0\0clusters›\ 3ÏÃÊ"Ÿ\ 1ÌÌËthrŽ‘\ fßo¹=Ÿú¹w‘\bÔ\15Ëf‘\0áÇoundcl\18Kuster<rsŽ‘\ 4ˆ…Ÿ\ 2ƒù‰\0\0\0>L\aŸ\ 6åêf‘\0áÇindabl•\18Kecl“uster<rsŽŽŽŽ‘D\a¿¹.‘\ 5/éHo•¬rw“ev“er‘\ 3ÏÄthe˜n“um“bSŽer˜of˜found–\ 3ÏÄclusters˜is˜not˜robust“as˜explainedŽ¡‘\ 2\0\0bSŽelo¬rw.‘\ 5.§Instead›\ 3Ëÿthe–\ 3ËþTPC‘\ 3Ë÷group“has˜in¬rtroSŽduced“a˜new“v‘ÿXäariable“-˜the“ratio˜of“n•¬rum“bSŽer˜of‘\ 3ËþcrossedŽ¡‘\ 2\0\0roš¬rws–\ 4Åito‘\ 4Åjthe“n˜um˜bSŽer›\ 4Åjof“\fndable˜clusters“-“whic¬rh˜is“almost˜indepSŽenden¬rt“on˜tracš¬rk“m˜ultiplicit˜yŽ¡‘\ 2\0\0and–\ 4[eÊ\11n9¹.‘\ 6‹\17A¬rt“the“end“of“this“section“a‘\ 4[drecommendation“on“what“v‘ÿXäariables“to“cut“on“in“order“toŽ¡‘\ 2\0\0ac•¬rhiev“e›\ 3ê¨go•SŽo“d˜ÊpŸ\ 1ÌÌËtŽ‘\a|r¹resolution˜and˜fak•¬re˜remo“v‘ÿXäal˜is˜giv“en.Ž¡¡‘\ 2\0\0TPC‘\ 4A@clusters–\ 4AVcan“bšSŽe“lost‘\ 4AUdue“to“unkno¬rwn“reasons“or“b˜ecause“their“c¬rharge“is“b˜elo¬rw“thresholdŽ¡‘\ 2\0\0(caused–\ 3Â\fbš¬ry‘\ 3Â\vthe“fron˜t-end“electronics;‘\ 3ϕthese›\ 3Â\vclusters“are“called˜missing“clusters).‘\ 5+VThe“thresholdŽ¡‘\ 2\0\0of–\ 4Vûthe›\ 4Vúcluster“\fnder˜approac¬rhes“the“digital˜threshold“(due“to˜the“1pad˜cluster“functionalit¬ry).Ž¡‘\ 2\0\0The–\ 4Õ¨unknoš¬rwn“reasons“summarize‘\ 4Õ©e\vects“suc˜h“as“dead“zones,‘\ 5\10imissing“partitions“and“deca˜ys.Ž¡‘\ 2\0\0Ê"Ÿ\ 1ÌÌËthrŽ‘\10\ en¹depSŽends–\ 3„Qon“the“digital–\ 3„Rthreshold,‘\ 3˜Èon“m•¬rultiplicit“y‘ÿ\ 5V,–\ 3˜Éenergy›\ 3„Qloss,“drift˜length˜and˜trac¬rk˜angle.Ž¡‘\ 2\0\0The–\ 3ê¨later“three“determine“simply“the“amplitude“of“the“signal.Ž¡‘\ 2\0\0The–\ 5\19kdepSŽendence›\ 5\19lof“Ê"Ÿ\ 1ÌÌËthrŽ‘\11£‰¹on“these˜is“sho¬rwn˜in“\fgures˜2(a)“and˜2(b)“for˜PbPb“data˜tak¬ren“inŽŽŸ\1e\0\0’\0ï\10\ 24ŽŽŒ‹\0\0\0\ 5\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0%à \ 2–\0\0 ýv\0\0 \ 2l\0\0 ý¹\0\0‘\ 2\0\0¹2010.‘\a5OThe›\ 4”#di\veren¬rt–\ 4”"colors“correspSŽond˜to“di\veren¬rt“energy˜loss.‘\a5OThe“lo•¬rw“est˜lying‘\ 4”"distributionŽ¤\ e€\0‘\ 2\0\0correspSŽonds–\ 4\e\fto“loš¬rw“energy“loss“the“one“o˜v˜erla˜ying“all‘\ 4\e\vhigh“energy“loss.‘\ 5Ê\fMultiplicit˜y“is“de\fnedŽ¡‘\ 2\0\0b•¬ry›\ 3ïæthe‘\ 3ïån“um“bSŽer˜of˜con“tributors˜to‘\ 3ïåthe˜TPC‘\ 3ïäv“ertex.‘\ 5HšF‘ÿ\ 5Vor–\ 3ïåbSŽetter˜visualization˜the˜plots“2(a)˜andŽ¡‘\ 2\0\02(b)–\ 3­Æare›\ 3­Åpro‘\0§\1cjected“in˜slices“of“m•¬rultiplicit“y˜and–\ 3­ÆÊ\11n9¹.‘\ 5$”Then“for“a˜giv¬ren“threshold,‘\ 3¹óa˜limit“remo¬rvingŽ¡‘\ 2\0\0the›\ 3\18Clo•¬rw“er–\ 3\18Dx%˜of˜the˜distribution,‘\ 3BXthe˜related“Ê"Ÿ\ 1ÌÌËthrŽ‘\ f¢`¹is˜determined.‘\ 4ò¿The˜output˜is˜sho¬rwn“in˜FiguresŽ¡‘\ 2\0\03(a)–\ 3ê¨and“3(b).‘\ 58àA“clear“depSŽendence“on“tracš¬rk“m˜ultiplicit˜y“and“Ê\11‘\ 4Xá¹is“seeable.Ž¡‘\ 2\0\0In–\ 5iäFigures“2(c)“and“2(d)“as“w¬rell“as“3(c)“and“3(d)“one“can“see“the“correspSŽonding“plots“forŽ¡‘\ 2\0\0the–\ 4I7ratio“of“n•¬rum“bSŽer–\ 4I7of‘\ 4I8crossed“roš¬rws“to“the“n˜um˜bSŽer“of“\fndable“clusters.‘\ 6TŽThe“ratio,‘\ 4`Ûthe“newlyŽ¡‘\ 2\0\0in¬rtrošSŽduced–\ 4Guv‘ÿXäariable,‘\ 4^©is“almost“indep˜endenš¬rt“from‘\ 4Gvenergy“loss,‘\ 4^¨m˜ultiplicit˜y‘\ 4Gvand“Ê\11‘\ 4µ®¹(z-direction).Ž¡‘\ 2\0\0The–\ 3ê¨dip“in“the“Ê\11n9¹-plot“is“due“to“the“crossing“of“tracš¬rks“with“the“cen˜tral“cathoSŽde.ŽŸ"Ê«‘\ 2\0\0Û2.1Ž‘&æcAv‘ÿ\19™ailable–\ 5ffV‘þ¦fariables“and“Cut“Recips3esŽŸ\16@\0‘\ 2\0\0¹Analyses–\ 3ê¨with“the“TPC“can“makš¬re“use“of“the“follo˜wing“QA“v‘ÿXäariables:Ž¤\18€\0‘\10\h1.ŽŽŽ‘\1f_ìNum¬rbSŽer–\ 3ê¨of“TPC“clustersŽ¡‘\10\h2.ŽŽŽ‘\1f_ìNum¬rbSŽer–\ 3ê¨of“\fndable“clustersŽ¡‘\10\h3.ŽŽŽ‘\1f_ìNumš¬rbSŽer–\ 3ê¨of“crossed“ro˜wsŽ¡‘\10\h4.ŽŽŽ‘\1f_ìNumš¬rbSŽer–\ 3ê¨of“clusters“in“crossed“ro˜wsŽ¡‘\10\h5.ŽŽŽ‘\1f_ìCoš¬rv‘ÿXäariance–\ 3ê¨matrix“elemen˜tsŽ¡‘\10\h6.ŽŽŽ‘\1f_ìAll–\ 3ê¨comš¬rbinations“and“ratios“of“the“items“abSŽo˜v˜eŽ¡‘\ 2\0\0T‘ÿ\ 5Vo›\ 58\16ac•¬rhiev“e˜go•SŽo“d–\ 58\17ÊpŸ\ 1ÌÌËtŽ‘\bÉà¹resolution˜for˜high˜momen¬rta“a˜cut˜on˜the˜n•¬rum“bSŽer˜of‘\ 58\17crossed˜ro“ws˜andŽ¤\ e€\0‘\ 2\0\0the–\ 3äÎcoš¬rv‘ÿXäariance‘\ 3äÏmatrix“elemen˜ts“are“recommended.‘\ 56íCuts“on‘\ 3äÏITS‘\ 3äÍremo˜v˜e“already“a“lot‘\ 3äÏof“fak˜es.Ž¡‘\ 2\0\0F‘ÿ\ 5Vurther›\ 3‰Qimpro•¬rv“emen“t‘\ 3‰Pis˜reac“hed–\ 3‰Pwith˜a“minimal˜cut“on˜the˜n•¬rum“bSŽer–\ 3‰Pof˜crossed“ro¬rws˜and“on˜theŽ¡‘\ 2\0\0ratio–\ 4±|of“n•¬rum“bSŽer–\ 4±|of“crossed‘\ 4±}roš¬rws“to“n˜um˜bSŽer“of“\fndable“clusters.‘\a]The“application“of“the“cutsŽ¡‘\ 2\0\0depšSŽends–\ 3ÿöon“the‘\ 3ÿ÷t¬ryp˜e“of“analysis,‘\ 4\ 5Je.g.‘\ 5xËthe“cuts“prop˜osed‘\ 3ÿ÷for“further“fakš¬re“remo˜v‘ÿXäal‘\ 3ÿ÷do“not“applyŽ¡‘\ 2\0\0for–\ 4…ÂV0›\ 4…Ãanalysis“(gamma“con•¬rv“ersion,–\ 4¬‰kinks,“etc.).‘\a
23/F‘ÿ\ 5Vor–\ 4…Âother˜t¬rypSŽes“of“analyses˜w¬re“recommendŽ¡‘\ 2\0\0to–\ 3çøaccept›\ 3çùonly“trac¬rks˜with“a˜ratio“of˜n•¬rum“bSŽer–\ 3çøof˜crossed“ro¬rws˜to“n•¬rum“bSŽer˜of–\ 3çø\fndable˜clusters“ofŽ¡‘\ 2\0\0larger–\ 3œÛthan“0.83.‘\ 5\1eñThis›\ 3œÚhas“the“adv‘ÿXäan¬rtage“of˜also“bšSŽeing“indep˜enden¬rt“of“one‘\ 3œÚmissing“partition“inŽ¡‘\ 2\0\0the–\ 3ê¨read“out“(see“Fig.‘\ 58à4).Ž¡‘\ 2\0\0Figure–\ 4\ 5,4›\ 4\ 5+sho¬rws“the“ratio˜of“n•¬rum“bSŽer–\ 4\ 5,of˜crossed“ro¬rws“to˜\fndable“clusters“for˜expSŽerimen¬rtal“dataŽ¡‘\ 2\0\0(pp–\ 459LHC10d)“and“for“the“respšSŽectiv¬re“MC‘\ 45%sample.‘\ 6\18“The“distribution“for“exp˜erimen¬rtal“data“hasŽ¡‘\ 2\0\0\ 4ª¨small‘\ 4ª©pšSŽeak“at“sligh¬rtly“b˜elo¬rw›\ 4ª©0.9“and“then˜increases“in“comparison˜to“the“MC‘\ 4ªwdistributionŽ¡‘\ 2\0\0slo•¬rw“er.‘\ 5\ 6«This–\ 3T\ais›\ 3T\bdue“to˜a“missing˜partition.‘\ 5\ 6ªDepSŽending˜on˜the“angle˜with“whic¬rh˜the“trac¬rk˜passesŽ¡‘\ 2\0\0the–\ 3ê¨missing“partition“up“to“all“clusters“are“correspSŽondingly“not“recorded.Ž¡‘\ 2\0\0Though–\ 2´givš¬ren‘\ 2µthe“anc˜hor›\ 2µruns“MC‘\ 2Âiwill˜not“follo¬rw“the˜time“depSŽendence˜due“to˜missing“partitionsŽ¡‘\ 2\0\0in–\ 4/•data.‘\ 6\a¦F‘ÿ\ 5Vurther›\ 4/”discrepancies“bSŽet•¬rw“een–\ 4/•MC‘\ 4/‚and“data“are˜due“to“di\veren¬rt˜spSŽecies“abundance.ŽŽŸ\1e\0\0’\0ï\10\ 25ŽŽŒ‹\0\0\0\ 6\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\06K \ 2–\0\0 ýv\0\0 \ 2l\0\0Ÿþ:占þšŽ\‘\aÿdïJPSfile="figures/new_ethres_vs_eta.pdf" llx=0 lly=0 urx=72 ury=72 rwi=2331 ŽŽŽŸ\ e€\0‘aªì²(a)‘\ 3à¢ó
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