Upload
cecile
View
47
Download
0
Embed Size (px)
DESCRIPTION
Analisi di dati del Run I. C ongregazione per la D ottrina della F ede. dal top al bottom con un pizzico di charm. P. Giromini. 5 analisi completate fra il 1999 ed il 2002 Usano campioni di dati diversi, ma hanno un filo logico comune - PowerPoint PPT Presentation
Citation preview
Analisi di dati del Run I
dal top al bottom
con un pizzico di charm
P. Giromini
Congregazione per la Dottrina della Fede
5 analisi completate fra il 1999 ed il 2002 Usano campioni di dati diversi, ma hanno un filo logico
comune 1: Heavy flavor properties of jets produced in p p
interactions at s1/2=1.8 TeV (blessata, draft in preparazione) 2: Studio di decadimenti semileptonici sequenziali
(b l c X, c l s X) (blessing frozen dopo 3 mesi di presentazioni, non si trovano sbagli ma il risultato non piace, analogo dei superjet)
3: Misura di time-integrated mixing parameter di adroni con beauty (presentata, blessing parte inizi ottobre)
4: Studio dello spettro di massa invariante di dimuoni fra la J/ e la (1S) (presentata, in coda)
5: Studio di eventi con J/ +leptone (analogo del BC) (presentata, in coda)
1Heavy flavor properties of jets produced
in p p interactions at s1/2=1.8 TeV
A small step forward in resolving the long-standing
discrepancy between the measured and predicted b-
cross section at the Tevatron
Jets with heavy flavor Over several years CDF has been comparing the
fraction of jets with heavy flavor (b and c quarks) to a simulation based upon the Herwig and CLEO (QQ) Monte Carlo generators
Heavy flavor-identification : EfficiencySECondary VerTeX (SECVTX) 50%Jet-ProBability (JPB) 50%
Data sets : W+ jet events, generic-jet data (JET20, JET50, and JET 100), di-jet events with one jet containing a lepton (low-pT lepton sample)
Jets with heavy flavor We have used the low-pT lepton
sample to calibrate the data-to-simulation scale factors for the SECVTX and JPB tagging algorithms
We have used generic-jet data to tune the parton-level cross sections evaluated in Herwig within experimental and theoretical uncertainties
W+jet events P~50%
PRD 64, 032002 (2001)
Jets with heavy flavor We also identify heavy flavors
by searching jets for semileptonic decays (SoftLeptonTagging ) efficiency 20%
PRD 65, 052007 (2002)
P~0.4%
P~50%
Anomalous W+ 2,3 jet events with a supertag
The kinematics of these events has a 10-6 probability of being consistent with the SM simulation [PRD 64, 032004 (2002)]
Some of us took these events very seriously; hep-ph/0109020 shows that the superjets can be modeled by postulating the existence of a low mass, strong interacting object which decays with a semileptonic branching ratio of the order of 1 and a lifetime of the order of 1 ps
Since there are no limit to the existence of a charge –1/3 scalar quark with mass smaller than 7 GeV/c2
[PRL 86, 1963 (2001)], the supersymmetric partner of the bottom quark is a potential candidate
Light sbottom (bs) Lot of very recent buzz hep-ph/0007318 uses it to resolve the long-standing
discrepancy between the measured and predicted value of R for 5 < s1/2 < 10 GeV at e+ e- colliders
PRL 86, 4231 (2001) uses it in conjunction with a light gluino which decays to b bs to explain the difference of a factor of 2 between the measured b-quark production cross section and the NLO prediction
If light bs existed, Run 1 has produced 109 pairs; why we did’t see them ?
Strategy the NLO calculation of p p bsbs predicts =
19.2 b for a squark mass of 3.6 GeV/c2 (Prospino MC generator program) .
The bb production cross section at the Tevatron is = 48.1 b (MNR)
The cc production cross section at the Tevatron is = 2748.5 b (MNR)
The NLO calculation has a >50% uncertainty because of the renormalization scale
Strategy We have adjusted the heavy flavor production cross sections
calculated by Herwig within the theoretical and experimental uncertainties to reproduce the rate of SECVTX and JPB tags observed in generic-jet data.
In that study we have used jets with with uncorrected ET>15 GeV and ||<1.5; they correspond to partons with transverse energy approximately larger than 18 GeV
For partons with transverse energy larger than 18 GeV, = 84 nb , = 298 nb , and = 487 nb (10% contamination)
we could have easily tuned the Herwig generator to explain in terms of SM processes an additional 10% pair production of scalar quarks: f= 382 nb , and f= 487 nb
Strategy What if there is a bs quark with a 100% semileptonic
branching ratio In b-quark decays, a lepton is produced in 37% of the cases In c-quark decays, a lepton is produced in 21% of the cases By requiring that at least one jet in the previous QCD data
contains a lepton (inclusive low-pT lepton sample or generic-jet data with SLT tags), the production cross sections are = 84 nb , = 110 nb , and = 102 nb (28% contamination)
By fitting a simulated pseudo-experiment which includes sbottom production with a conventional QCD simulation using rates of SECVTX and JPB tags, one might find f= 194 nb , and f= 102 nb
Strategy As a next step, we select events in which an additional jet
contain a soft lepton (57% contamination) If the data are due to bottom and charmed quark production
only, we will find = 93.4 nb (71.8 nb due to b-quarks and 21.6 nb due to c-quarks) in the data and the simulation
If the data contain bs production, the cross section in the data will be = 146.3 nb (40.7 nb due to b-quarks, 21.6 nb due to c-quarks, and 84.0 nb due to scalar quarks)
In generic-jet data with SLT tags, one would find = 244 nb without a scalar quark, or , with a scalar quark, = 296 nb in the data and = 244 nb in the simulation
Use generic-jet data to cancel out experimental uncertainties (efficiencies, fake removal,…)
Data sample Events with 2 or more jets with ET > 15
GeV and at least two SVX tracks (taggable,|
one electron with ET> 8 GeV or one muon with pT > 8 GeV/c contained in one of the jets
Require I > 0.1 Reject conversions Apply all lepton quality cuts used in
the high-pT lepton sample
68544 events with an electron jet and 14966 events with a muon jet
away jet
lepton jet
l
Perform a detailed comparison between data and simulation using SECVTX, and JPB tags on both the lepton- and away-jets
Differently from previous CDF analyses, this study checks at the same time the cross section for producing at least 1 b with |imperfect NLO calculation), 1 b +1 b with |apparently robust NLO calculation)
Then we check the semileptonic branching ratio of heavy flavor hadrons by counting the number of a-jets with SLT tags in the data and in the simulation
Strategy
Mistags and tagging efficiencies PRD 64, 032002 (2001) Mistags (tags in a jet without heavy flavor) are evaluated with
parametrized probability functions derived in generic-jet data. We estimate a 10% uncertainty.
Since we use a parametrized simulation of the detector, we have measured the data-to simulation scale factor for the tagging efficiency of the SECVTX and JPB algorithms.These factors were determined with a 6% accuracy and implemented into the simulation.
The SLT simulation uses efficiencies for each selection cut measured using data; we estimate a 10% uncertainty, which includes the uncertainty on the semileptonic branching ratio
The SLT efficiency in supertags is corrected for the data-to-simulation scale factor measured in generic-jet data: (85±5)%
Simulation Use the Herwig generator program (option 1500, generic 2 2 hard
scattering with pT > 13 GeV/c) bb and cc production are generated through processes of order
such as qq bb Processes of order are implemented through flavor excitation
diagrams, such as g b g b, or gluon splitting, in which the process g g g g is followed by g bb
Use MRS (G) PDF’s The bottom and charmed hadrons are decayed with QQ (version
9_1) We select simulated events which contain hadrons with heavy flavor
and at least one lepton with pT > 8 GeV/c These events are passed through QFL, a parametrized simulation of
the CDF detector and treated as real data We have simulated 27156 electron events (98.9 pb-1) and 7267
muon events (55.1 pb-1) with heavy flavor
Evaluation of the heavy flavor content of the data
Before tagging, approximately 50% of the lepton jets do not contain heavy flavor; they are mostly due to fake leptons
Mistags in the lepton-jets and away jets are evaluated with a parametrized probability and removed
The fraction (1-hf) of events in which the l-jet does not contain heavy flavor is not simulated. In these events, away-jets can have tags due to heavy flavor. Their rates are estimated using a parametrized probability of finding a tag due to heavy flavor in generic-jet data. Using a sample of l-jets containing electrons due to identified conversions, we estimate a 10% accuracy. It is a slight overestimate.
away jet
lepton jet
l
Fit of the simulation to the data Use 6 fit parameters corresponding to the direct, flavor excitation and
gluon splitting production cross sections evaluated by Herwig for b and c-quarks
Ke and Kaccount for the luminosity and b-direct production The parameters bf, bg, c, cf, cg account for the remaining production
cross sections, relative to the b-direct production The ratio of b to c direct production constrained to the default value
(about 1) within 14% the ratio of b to c flavor excitation constrained to the default value
(about 0.5) with a 28% uncertainty bg constrained to (1.4±0.19) cg constrained to (1.35±0.36) The tagging efficiencies are also fit parameters, and are constrained
to their measured values within their uncertainties (6% for b-quarks, 28% for c-quarks)
Fit result
2/DOF=4.6/9
Fit result
Fhf = (45.3±1.9)% for electrons
Fhf = (59.7±3.6)% for muons
Kinematics
SECVTX tagged
KinematicsSECVTX tagged
KinematicsL -jet SECVTX tagged
A-jet
A-jet with
SECVTX tags
KinematicsL -jet SECVTX tagged
KinematicsL -jet SECVTX tagged
A-jet with
SECVTX tags
Comparison of a-jets with SLT tags in the data and the normalized simulation
SEEN 1137±140.0 (±51.0
STAT.)
EXPECTED 746.9±75.0 (SYST)
SEEN 453±29.4 (±25 STAT.)
EXPECTED 316.5±25.4 (SYST)
(±15.8 SLT efficiency, ±20 fit)
Systematics (away-jets with SLT tags)
In events due to heavy flavor, there is an excess of 391 a-jets with a SLT tag with respect to the simulation (1137.8 observed and 746.9 expected), having removed 619.3 fake tags [the events in which the l-jet does not have heavy flavor contain 901.9±91 a-jet with SLT tags (74% fake+ 26% heavy flavor): slight overestimate].
If one could increase the fake rate in events with heavy flavor by 60%, the excess would disappear. However, in generic-jet data, the fake rate is already 74% of the SLT tagging rate.
Since fakes are approximately 74% of the SLT rate, the 10% uncertainty of the fake removal was evaluated by comparing observed rates of SLT tags to the parametrized prediction in all QCD samples. Most of the 10% comes from the fact that different QCD sample have slightly different heavy flavor purity
Systematics (fake SLT tags)
The heavy flavor content of generic-jet data has been evaluated using SECVTX and JPB tags
In generic-jet data the number of SLT tags due to heavy flavor is therefore known with a 13% error, mostly due to the 10% uncertainty of the SLT tagging efficiency
Therefore the real uncertainty on the fake rate is no larger than 2.6%
Data – simulated H.F. = 15783±423 fakes
Parametrized SLT fakes 15570
Systematics (fake SLT tags) Away-jets in the inclusive lepton have a higher
heavy flavor content (26%) than generic-jet data (13%) .
Could the fake rate in jets with heavy flavor be anomalously large ? Could the SLT efficiency or the semileptonic branching ratio in the simulation be grossly wrong ?
Jets with SECVTX or JPB tags in generic-jet data have a heavy flavor content ranging from 86% (JET 20) to 71% (JET 100) . The rate of SLT tags in these jets is not higher than in the simulation
This does not support simulation deficiencies as an explanation for the discrepancy
h.f . fakes
low pT (SLT) 1138 619
SECVTX+SLT 944 507
JPB+SLT 1167 856
Conclusions We have measured the heavy flavor content of the low pT
inclusive lepton sample by comparing rates of SECVTX and JPB tags in the data and the simulation
We find good agreement between the data and the simulation tuned within the experimental and theoretical uncertainties
We find a 50% excess of a-jets with SLT tags due to heavy flavor with respect to the simulation; the discrepancy is a 3.5 systematic effect due to the uncertainty of the SLT efficiency and background subtraction. However, comparisons of analogous tagging rates in generic-jet data and their simulation do not support any increase of the efficiency or background subtraction beyond the quoted systematic uncertainties
Conclusions A discrepancy of this kind and size is expected, and was the
motivation for this study, if pairs of light scalar quarks with a 100% semileptonic branching ratio were produced at the Tevatron
The data cannot exclude alternate explanations for this discrepancy
Previously published measurements support the possibility, born out of the present work, that approximately 50% of the presumed semileptonic decays of heavy flavor hadrons produced at the Tevatron are due to unconventional sources
correlated +b-jet cross section
PRD 53, 1051 (1996) 90% of the cross section at
Data are 1.5 times larger
than the NLO calculation The NLO cross section is
not very sensitive to the scale
The NLO value is approximately equal to the Born value
bb•BR
bb correlations (dimuons)
PRD 55, 2547 (1997) Data are 2.2 times larger
than the NLO calculation D0 has a similar result The dependence of the
NLO prediction on the scale is less than 20%
Born and NLO values are within a few percents
bb•BR2
2Study of sequential semileptonic decays of b-hadrons
produced at the Tevatron
Given the previous anomaly, it is of interest to study sequential semileptonic decays of hadrons with heavy flavor
We use the same data set and simulation of the previous analysis
Comparison of data and simulation
Data: 1447±65 dileptons (±44 stat. and ±48 syst.)
Sim.: 1181±129 dileptons (±51 fit and sim. stat., ±118 SLT eff.)
2 effect
Dilepton kinematics
Dilepton kinematics
Systematics (fake dileptons) “Misidentified leptons are expected to be present in
equal amount in OS and SS dileptons” [PRD 49].The technique of subtracting SS from OS dileptons to remove this background has been used many times in CDF [PRD 49 (1994), PRD 59 (1999)].
In contrast with previous analyses which used this technique, we now find a discrepancy between the data and the simulation prediction. We want to investigate further. Use the electron sample only (larger statistics)
Fake dileptons The heavy flavor simulation of the inclusive electron sample, after
normalization, contain 955 ± 108 OS and 63 ± 9 SS dileptons In the data, there are 1450 OS and 399 SS dileptons To get rid of this discrepancy, one would like to explain in terms of
background 495 ± 114 OS and 276 ± 20 SS dileptons (R=1.79±0.43) On average, a jet contain the same number of positive and negative
lepton-candidate tracks. When searching for a second lepton in a jet in which one track has
been already identified with an electron, one expects the number of OS candidates to be larger than the number of SS candidates [Nc(OS)=54938 and Nc(SS)=34744] (R=1.58)
If this is correct, there is no dilepton excess, but a number of previous analyses are wrong
Dilepton background (conclusions)
Applying the parametrized fake probability to the Nc(OS) candidates one gets OS=302 ± 30 [used in PRD 60, (1999)]
However, the standard fake parametrization derived from generic-jet data might not be adequate to describe the fake rate in jets which already contain a lepton with pT> 8 GeV/c
Use generic-jet data to derive a fake probability for jets which already contain a lepton
Dileptons (generic-jet data)
Dilepton background (conclusions)
When applying P(OS) and P(SS) of generic-jet data to the candidate tracks, one predicts 236 ± 44 OS and 229 ± 14 SS fake dileptons
Note that b-hadron mixing is not simulated; when using =0.118, the simulation predicts 915 ± 105 OS and 103 ± 15 SS dileptons due to heavy flavor; the difference between the data and the heavy flavor expectation is 535 ± 111 OS and 236 ± 24 SS dileptons
P(SS) of generic-jet data provides the correct prediction of SS dileptons
A background of 276 events with a 10% accuracy seems to be a fair estimate of the fake OS dileptons
Sequential b-decays
According to the simulation, most of the dileptons in the same jet are contributed by semileptonic cascade decays of b-hadrons. They are simulated with the QQ Monte Carlo program. How good is it ?
Help from DELPHI (2000-060 PHYS 861, 2000) DELPHI compares 573474 hadronic Z-decays to a JETSET 7.3
simulation consisting of 992988 events normalized to the same luminosity of the data
Use events with |cos T|<0.95, where T is the thrust axis Select events with two leptons with pT > 3 GeV/c and | |<1 in the same
emisphere as defined by the thrust axis. Divide events in OS and SS First show agreement between DELPHI data and simulation. Then,
show agreement between the DELPHI and our simulations at the Z-pole
DELPHI
Sequential b-decays
DELPHI simulation: comparison
between OS-SS dileptons and
sequential b-decays identified at
generator level
Comparison between our and DELPHI
simulation at the Z-pole
3Ratio of like-sign to opposite-sign dileptons
Recent publications by Ed Berger et al. explore an explanation within the context of MSSM to the discrepancy between the measured cross section and the NLO prediction
Hep-ph/0103145 postulates the existence of a light gluino which decay to b and
The pair production of gluinos provides an inclusive b-cross section comparable to conventional QCD production
However, pair production of gluinos and subsequent decays to b quarks also leads to an increase of like-sign dileptons
bb
b~
The like-sign dilepton increase could be confused with an enhanced B0-B0 mixing and in a value of the time-integrated mixing parameter, larger than the world average 0.118±0.005
Hep-ph/0103145 predicts and, after comparing to the CDF Run 1A result of 0.131±0.026, concludes that a better measurement is needed in Run II
Other results: UA1 measured and CDF (Run 0)
We repeat the Run 1A analysis using also Run 1B dimuons and e-
Method of analysis Use the same method of RUN 1A: fit the impact
parameter distributions with the expected distributions for various sources
The main sources of dileptons are semileptonic decays of charmed and bottom mesons, and prompt decays of onia and Drell-Yan production
Impact parameter distributions for b and c quarks are derived from a simulation which uses Herwig (option 1500), QQ version 9_1, and QFL’
Prompt shape The prompt shape is derived
using muons from 1S) decays (9.28< M <9.6 GeV)
The background is removed using dimuons with 9.04< M <9.2 and 9.54< M <9.7 GeV
Shapes
Ratio of numbers of leptons with d<0.008 to that with d>0.008 cm
b quarks 0.85 c quarks 2.03 prompt 32.3
Shapes Since there are two leptons the fit is performed in the
two-dimensional space of the impact parameters The impact parameters of each lepton are
uncorrelated variables Use a binned maximum log likelihood method with
the same binning used for the Run 1A analysis Fit BB, CC, PP, BP, and CP combinations
Dimuons with invariant mass > 5 GeV/c2
18420 OS 9279 LS
Removed 6264 OS and 1302 LS with 9.2 < M <10.5 GeV
Fit result R=BB(LS)/BB(OS)
=0.600±0.022 CC/BB(LS+OS)=0.33 ±0.03
e-events
4331 LS7802 OS
e-events
R=BB(LS)/BB(OS) =0.597±0.028
CC/BB(LS+OS)=0.23 ±0.03
Time integrated mixing parameter
R=
With f=2 f f) f= 0.123 ± 0.015 (1A syst.) and f=0.2157±0.0226 (syst.)
f= f e+ ffe ff e = 0.06, f= 0.142 and f=0.185±0.0161 (syst.)
= 0.168±0.011 (dimuons) = 0.184±0.013 (e )
f [21- ] +f) (1-f) [22f
(stat.) ±0.01 (syst.)
bb cross section (dimuons) the number BB(OS+LS) corresponds to a cross section
which is a factor of 2.2 larger than the NLO prediction D0 has a similar result For dimuons b-quarks with pT> 6.5 GeV/c and |
the ratio NLO/Born(LO) is 1.05 (not 2 as for the inclusive b cross section)
The dependence on thescale (is ±20% and not ±50% as for the inclusive b cross section
the inclusive NLO cross section can be easily adjusted by a factor of two, but not the NLO cross section for 2 b-quarks with pT> 6.5 GeV/c and |
Ratio of cc to bb production (dimuons)
CC/BB(LS+OS)=0.33 ±0.013 (present fit) D0 has also a measurement of the bb cross section using dimuons
with pT> 4 GeV/c and |The various contributions are disentangled with fits to the pT
rel distributions. D0 finds CC/BB(LS+OS)=0.31 ±0.09 In the simulation CC/BB(LS+OS)=0.18 ±0.02 for us, and 0.13 ±0.03
for D0 Is the Herwig simulation all right ? UA1 also measured the bb cross section using dimuons with pT> 3
GeV/c. The various contributions are disentangled with fits to the pTrel
distributions, but the ratio CC/BB(LS+OS) is forced to be 0.13±0.06 as expected from the ISAJET simulation
Ratio of cc to bb production CC/BB(LS+OS)=0.23 ±0.03 in edata In the esimulation (15000 events generated with option 1500 of
Herwig) CC/BB(LS+OS)=0.13 How reliable is the simulation ? In the NLO calculation (MNR) the ratio of the bb to cc cross section
for producing heavy quarks with |and transverse momentum large enough to produce an electron with ET >5 GeV and a muon with pT >3 GeV/c is 0.72
The CASCADE generator (hep-ph/0109146) models correctly the inclusive b-cross section measured by CDF and DO .With this generator we find BB/CC=0.74
In Herwig, this ratio is 0.73 We start seeing another problem: the cc cross section is a factor of 4
larger than the NLO calculation
Deviation from the conventional QCD expectation
The measured bb cross section (2 x NLO) and the value of agree with the Berger’s prediction
However, if Berger was right we also should have found CC/BB(LS+OS)=0.06 and not 0.23 ±0.03 as in edata
4Search for 1-- bound states of scalar quarks
SPEAR set a ll= 100 eVlimit to such states The expectation is ll= 10-30 eV(Nappi) In the reasonable assumption that production and
decay proceed via three-gluon exchange B= Y(1s) B x R, with R= (mY/m)3 x Y
Y =1.32 KeV and R=2-6 % We have 104 Y(1S) and one expects >200
eV, also in a simulation
eV in a simulation
A 150 MeV bin (±2 contains 9000 events
Background reduction As seen in the previous
analysis, 78% of the dimuons with invariant mass larger than 5 GeV are due to heavy flavor
Cut on isolation and impact parameter significance
Tune the cuts on the Y(1S) to have >90% efficiency
The background is cut by a factor of 3
Fit result Resolution fixed (38
MeV) Mass 7.2 GeV 250±61 events 3.5 effect
5: search for Bc sb sb is approximately 15% of b b
~
b (bs) c
c c
ls
J/
In the assumption that the bs semileptonic branching ratio is 100% for a bs quark and 20% for a b quark the channel J/+l+X is equally contributed by the Bc and Bc
~
Bc discovery Uses electrons with pT >2
GeV/c and |1.0 , but muons with pT > 3 GeV/c and |0.6
Signal of about 20 events; given the lifetime the cross section x BR is a factor of 2 larger than expected in units of B J/ K
By using muons with |1.0 and pT > 2 GeV/c we increase the acceptance by more than a factor of 4 without degrading the signal to noise ratio
J/+l+X
Slides di supporto
Data
Heavy flavors in the simulation are identified at generator level
Fit result-parameter corr. coeff.
For
NLO and Herwig calculations Herwig ignores interference terms between the Born
approximation and the NLO diagrams, and evaluates a gluon splitting+flavor excitation contribution which is a factor of 3 larger than the Born approximation.
In the NLO calculation the contribution of the Born cross section and of the gluon splitting+flavor excitation are approximately equal using the renormalization scale when using the scale the scale the NLO calculation gets closer to Herwig.
The fact that the ratio between NLO and Born is about two and is not stable as a function of the renormalization scale is taken by the experts as an indication that NNLO corrections are important
The relevance of the Herwig result, which models the data, is the indication that the effect of NNLO correction should be that of canceling the interference terms
NLO and Herwig calculations However, in this specific analysis we are interested in comparing
rates of a-jet with heavy flavor (signaled by SLT or SECVTX tags) in events in which the l-jet has also heavy flavor
These jet have | |<1 and corresponds to partons with ET > 18 GeV In this case Herwig evaluates that the gluon splitting+flavor
excitation contribution are 40% of the Born contribution and not a factor of 3 higher
For this type of kinematics, the ratio of the NLO to Born calculations is also of the order of 1.1-1.3. In addition, for this topology, the NLO calculation depends little on the choice of and it appears to meet general criteria of robustness.
KinematicsL -jet SECVTX tagged
A-jet
A-jet with
SECVTX tags
KinematicsL -jet SECVTX tagged
A-jet with
SECVTX tags
KinematicsL -jet SECVTX tagged
A-jet with
SECVTX tags
fragmentation in generic-jet data
550,000 generic-jet events in the data and in the Herwig simulation (JET20, JET50, and JET100). 1324 supertags in the data1342 simulated supertags
away-jets with SLT tags
No dependence of the result from the fit normalization
Nb and Nc are the numbers of predicted a-jets with bottom and charmed flavor
bJPB=0.40, c
JPB=0.20, bSLT=0.058, c
SLT=0.029 HFTSLT(a-jet)= b
SLT (Nb + 0.5 Nc) bJPB /b
JPB = b
SLT /bJPB HFTJPB(data) =
bSLT /b
JPB (5126.6±146.7) =743±78
Independent of the heavy flavor composition of the fitted simulation
No dependence of the result from the fit normalization
In other words Remove, e.g., the 14% constraint on c/b=1 The fit returns c=2.8±1.6 However, HFTSLT(a-jet) =597.6±69.3 603±66
(electrons) 149±21 156±21 (muons)
Systematics (away-jets with SLT tags) In the fitted simulation, 79% of the a-jets with an SLT tag due to
heavy flavor are attributed to b-production The fraction of SLT tagged jets is higher for b-production (2%) than
for c-production (1%) If one could increase the b-purity from 79% to 100%, the predicted
number of SLT tagged a-jets would increase from 747 to 839, closer to the observed 1138 ± 120
Check the b-purity by comparing the numbers of l+ D0, l +D±, and l +non-prompt J/combinations in the data and the fitted simulation
b-purity
D0 : 126.0 ± 15.5 in the data and 139.9 ± 15.0 in the simulation
D± : 73.7 ± 17.8 and 68.5 ± 14.1
J/: 90.8 ± 10.1 and 101.9 ± 11.4
Ratio of the b-purity in the simulation to that in the data is 1.09 ± 0.11
D0
D±
Same flavor OS-SS dileptons 2.6 < mee< 3.6 GeV/c2
2.9 < m< 3.3 GeV/c2
259 ± 17.2 and 209.2 ± 23.7 (before tagging)
89.7 ± 10.5 and 100.5 ± 12.4 (SECVTX)
90.8 ± 10.1 and 101.9 ± 11.4 (JPB)
Cross check with J/ mesons from B-decays
In generic-jet data we do not observe any excess of jets with SLT tags or supertags
We do observe an excess after enriching the b-purity of the QCD data by requiring a lepton-jet
We study a sample of jets recoiling J/ mesons from B-decays. We use the same J/ data set and selection used for the measurement of the J/ lifetime and fraction from B-decays
1163 J/ over a background of 1179 events estimated from the side-bands (SB)
J/ lifetime
The number of J/ mesons from B-decays is N= ()-SB+–SB-) =561, which is 48% of the initial sample
In the 572 away-jets we find 48.0 ± 15.1SECVTX, 61.7 ± 17.3 JPB tags, and –9.4 ± 14.4 SLT tags
In the simulation we expect 8.1 ± 1.1 SLT tags
Dilepton kinematics