# Presentation: 001000

## Anomalies in Heavy Flavor Jets at CDF

**G.Apollinari-Fermilab**
*For the CDF Collaboration*
**Les Rencontres de Physique de la Vallée d’Aoste**
** ****LaThuile **
**March 5****th****,2004**

## Anomaly in W+2,3 jet Events at CDF

***	******PRD 65, 052007(2002)***

* **CDF Data sample used in top quark measurements*
* **Heavy Flavor Ident. (tagging) methods **	**	**	**	**	**b**	**c*
* **SECVTX**	**	**         **43%          9%*
* **JPB **	**	**         **43%       30%*
* **Soft Lepton Tagging       **6.4%       4.6%*
*Supertag (or superjet): jet containing both a SECVTX and an SLT tag.*

## No limit on the existence of a charge –1/3 scalar quark with mass smaller than 7 GeV/c2  (the supersymmetric partner of the bottom quark, bs, is a potential candidate) -  PRL 86, 4463 (2001). 

*Superjets modeled by postulating a low mass, strong interacting object which decays with a semileptonic branching ratio of  ~ 1 and a lifetime of ~1 ps - **hep-ph/0109020** *
*No limit on the existence of a charge –1/3 scalar quark with mass smaller than 7 GeV/c**2 ** (the supersymmetric partner of the bottom quark, **b**s**, is a potential candidate) -  **PRL 86, 4463 (2001). *
*This analysis is intended to search for evidence either supporting or disfavoring this hypothesis.*
*hep-ph/0007318** and **hep-ph/0401034 **use it to resolve the  discrepancy between the measured and predicted values of  *R * for 5 < ****s** **< 10 GeV and for  20 < ****s** **< 209 GeV  at e**+** e**-** colliders** *
*If  light **b**s **existed, Run I has produced 10**9 **pairs; why didn’t we see them ?*

## 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 single-b production cross section and the NLO prediction.

*PRL 86, 4231 (2001)** uses it in conjunction with a light gluino which decays to **b b**s **to explain the difference of a factor of 2  between the measured single-**b** production cross section and the NLO prediction.*
*Necessary but not sufficient condition*
*NLO not robust *
* *

## However....

* **Some interesting CDF & DǾ disagreements   between Data and Simulation:*
* **b+**** Production Cross-Section: ****bb** **. **BR*
* **Data are 1.5 times larger than NLO calculation, LO and NLO calculations are comparable*
* **PRD 53, 1051 (1996)*
* **bb**** ****+****-** Correlations: ****bb** . **BR**2*
* **Data are 2.2 times larger than NLO calculation, LO and NLO calculations are within a few percent*
* **PRD 55, 2547 (1997)*
*Phys.Lett. B 487, 264 (2000)*

* **Hint: Data-Simulation discrepancy could increase  with the  number of leptons in the final state*
* **Other necessary but not sufficient condition*

**Notes:**
The open circles are the model prediction for a renormalization scale of mu/2 minus the model prediction for m divided by model 

## Situation

*The NLO calculation of  **p p **** b**s**b**s ** predicts ** ****bs** = 19.2 ****b **for a squark mass of 3.6 GeV/c**2 **(Prospino MC generator program)** **.*
***bb** = 48.1 ****b **(NLO)*
***cc** = 2748.5 ****b** **(NLO)*
*We have used a generic jets data sample with E**T**>15 GeV and |****|<1.5  (corresponding to partons with E**T** larger than 18 GeV) to calibrate the simulation by using measured rates of SECVTX and JPB. *
*Can easily “bend” any Heavy Flavor generator or NLO calculation to explain in terms of SM processes an additional 10% production of scalar quarks*

***bs  **= 84 nb (Prospino MC)*
***bb** = 298 nb **(NLO)*
***cc** = 487 nb** **(NLO)*

*PRD 64, 032002 (2001)*

##                              (nb)                    bs(%)           tuned QCD       QCD

*	**Could tune generic jets and absorb the b**s** production into the b-quark production.....*

*	**...**and then require the presence of a Semileptonic decay (in b-decay a SLT is produced in 37% of the cases, while in c-decay a SLT is produced in 21% of the cases) to start seeing a deviation from the tuned expectation...*

*	**...**and see an even larger deviation (~2) when 2 Semileptonic decays are requested in the generic jet sample. This approach, however, would be open to arguments on the Lepton Identification Efficiency. *

*	**Alternatively, to avoid problems with the Lepton ID efficiency, the data can be tuned to the QCD Simulation AFTER the Semileptonic decay has taken place (this data sample corresponds to the Lepton-trigger data sample) using SECVTX and JPB tags. The tuning would avoid ****bb** theoretical uncertainties and uncertainties in the triggering lepton ...*

*	**...**and** **require a second SLT in the event to define the Signal Sample (SS) ...*

*	**The Control Sample is used to calibrate the SLT efficiency in the simulation and a comparison between the S.S. and the C.S. could have a discrepancy of ~30%. *

-                             ****** ****(nb)                    b****s****(%)           tuned QCD       ********QCD**
******b        c       b****s     ****total                      b       c       total**
** ****generic jets tuned          298     487    84    869      10%        382   487     869      1**
** ****g. j. t. x BR                     110     102    84    296      28%        141  102     243      1.2****    **

-                             ****** ****(nb)                    b****s****(%)           tuned QCD       ********QCD**
******b        c       b****s     ****total                      b       c       total**
** ****generic jets tuned          298     487    84    869      10%        382   487     869      1**
** ****g. j. t. x BR                     110     102    84    296       28%        141  102     243      1.2     **
** ****g. j. t. x BR****2                                ****41      22     84    147       57%          52    21        73      2**** **

-                             ****** ****(nb)                    b****s****(%)           tuned QCD       ********QCD**
******b        c       b****s     ****total                      b       c       total**
** ****generic jets tuned          298     487    84    869      10%        382   487     869      1**
** ****g. j. t. x BR                    110     102    84    296      28%        141  102     243      1.2     **
** ****g. j. t. x BR****2                               ****41      22     84    147      57%          52    21        73      2**** **
** ****g .j. x BR  tuned            110     102    84    296      28%        194  102      296      1   **
** ****(or lep-trig. evts)     **
** **

-                             ****** ****(nb)                    b****s****(%)           tuned QCD         ********QCD**
******b        c       b****s     ****total                      b       c       total**
** ****generic jets tuned          298     487    84    869      10%        382   487     869      1**
** ****g. j. t. x BR                    110     102    84    296      28%        141  102     243      1.2    CS **
** ****g. j. t. x BR****2                               ****41      22     84    147      57%          52    21        73      2 **
** ****g .j. x BR  tuned            110     102    84    296      28%        194  102      296      1   **
** ****(or lep-trig. evts)     **
** ****lep-trig. evts. x BR          41       22   84     147      57%          72    21       93      1.5    SS**

## Models to predict Heavy Flavor Production

***HERWIG vs Exact NLO Calculation***

*	**Scattering with 2 b-partons in the final state*

*	**Scattering produces a gluon recoiling against 1 or 2 b-hadrons in the final state*

**Notes:**
	In herwig si va a ordini superioni in frammentazione emettendo gluoni

## HERWIG vs Exact NLO Calculation

***HERWIG vs Exact NLO Calculation***

- HERWIG

*	**NLO/LO terms can be different for different models (NLO/LO~4 for HERWIG, NLO/LO~2 for NLO Calc.).*

*	**Fraction of away h.f. jets in detector acceptance is different for LO vs. NLO terms*

*	**Use tools to disentangle bb from cc production*

- Exact NLO

##                              (nb)                    bs(%)           tuned QCD       QCD

-                             ****** ****(nb)                    b****s****(%)           tuned QCD       ********QCD**
******b        c       b****s     ****total                      b       c       total**
** ****generic jets tuned          298     487    84    869      10%        382   487     869      1**
** ****g. j. t. x BR                    110     102    84    296       28%        141  102     243      1.2     **
** ****g. j. t. x BR****2                               ****41      22    84    147       57%          52    21        73      2**

***Generic Jet Control Sample***
*The simulation of the SLT algorithm uses efficiencies derived from the data (conversions, Z’s and **mesons decays)*
*Use generic-jet data to calibrate and cross-check the efficiency for finding SLT tags and supertags.*
*Efficiency for finding supertags empirically corrected by 15%*

***#2***

## away jet

- lepton jet

*l*

*Use sample enriched in Heavy Flavor content*
*Events with 2 or more jets with E**T **> 15 GeV and at least two SVX tracks (taggable,|****|<1.5)*
*one electron with E**T**> 8 GeV or one muon with p**T** > 8 GeV/c contained in one of the jets*
*Counting Experiment:*
*Determine the b- and c-quark composition of the data by counting the number of  SECVTX, and JPB tags on both the lepton- and away-jets*
*Check the semileptonic branching ratio of Heavy Flavor hadrons by counting the number of a-jets with a SLT and in the data and in the simulation*

##  Tuning the Simulation to the data 

- away jet

- lepton jet

*l*

*“**Kitchen Dirty Work” :*
*Mistags evaluated with parameterization (10%)*
*SECVTX-JPB tagging efficiencies measured in data (6%)*
*SLT Efficiency uncertainty (10%)*
*Simulated supertag efficiency (SECVTX+SLT or JPB+SLT) is corrected for the data-to-simulation scale factor measured in the generic-jet sample (85****5%).*
*Take care of tagging rates in the fraction of lepton-trigger events with no h.f. using a parameterized probability of finding a tag due to heavy flavor in generic-jet data. *

##        Addressed Issues

***Tuned HERWIG***

*F**hf **= (45.3±1.9)% for e *
*F**hf **= (59.7±3.6)% for ***

- NLO Calculation

-        _*Addressed Issues*_
* **b-quark fragmentation*
* **k**T** factorization (CASCADE)*
* **Berger’s model (gluinos)*
*Single b cross sections derived from 2 b cross sections using NLO  prediction*

**Notes:**
Addition intrinsic kt kick may improve agreement with data.

## a-jet with SECVTX tags

*a-jet with SECVTX tags*

*a-jet*

##                              (nb)                    bs(%)           tuned QCD       QCD

-                             ****** ****(nb)                    b****s****(%)           tuned QCD       ********QCD**
**g .j. x BR  tuned            110     102    84    296      28%        194  102      296      1   **
** ****(or lep-trig. evts)     **
** ****lep-trig. evts. x BR          41       22   84     147      57%          72    21       93       1.5  SS**

***Comparison of a-jets with SLT tags in the data and the tuned 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)*

*~3 **** discrepancy, with errors dominated by systematic effects*

**Notes:**
Effetto 3 sigma sistematico
Equalmente diviso
Efficienza SLT 10%
Sottrazione fondo 10%
Vediamo se possone esserre piu’ grosse

## Supertags

*Data-Simulation comparison for the yield of R (R’), the ratio of number of jets with a SECVTX (JPB) and SLT tag – supertags - to that with a SECVTX (JPB) tag in the generic jet sample and in the Lepton-trigger sample.*
*The tuned QCD Simulation predicts the same yield of supertags in generic jet and lepton-trigger jets*
*Data show a ~30% discrepancy between supertags in generic jets and lepton-trigger jets. *
*Systematic uncertainties in the SLT simulated efficiency would shift in the same direction the yield R in the generic jets sample and lepton-trigger sample. *

**Notes:**

MC is OK In dati different, but simile errore sistematico

##                                                    observed             pred. fakes.          pred. h.f.

*SLT mistags and tagging efficiency have been determined historically on data (PRD - 64, 032002) with conservative errors of 10% .*
*The availability of a tuned simulation can be used to reduce the previous estimate of the SLT mistags and tagging efficiency systematic errors. *
*Fit observed rates of SLT tags in generic jets with                              *
*P**f** x fakes +P**hf** x h.f.** *
*The fit returns P**f** =1.017±0.013 and P**hf** =0.981±0.045, **** = -0.77 *
*Using this result the SLT expectation in in the SS away-jets is 1362±28 whereas 1757±104 are observed (3.8 ****) *
*This discrepancy cannot come from obvious prediction deficiencies*

-                                                    observed             pred. fakes.          pred. h.f.
- SLT’s in  g. jets                                                     18885               15570±1557      3102 ±403
- SLT’s  in  g. jets with  SECVTX            1451                  999 ±60             508 ±51
- SLT’s  in g. jets with JPB                       2023                  856 ±86           1175 ±71
- SLT ‘s in a-jets (lep-trig.)                                 1757                       619 ±62            747 ± 75

## Conclusions

*We have measured the heavy flavor content of the  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 ****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 30% of the presumed semileptonic decays of heavy flavor hadrons  produced at the Tevatron are due to unconventional sources*

## Support Slides

##  Tuning the Simulation to the data 

*K**e**  and K****account 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*

| SECVTX | lepton side |
| --- | --- |
|  | away side |
|  | Both |
|  |  |
| JPB | lepton side |
|  | away side |
|  | Both |

*** ******Tuning the Simulation to the data****** ***

|  Fit parameters | Constraints | Error |
| --- | --- | --- |
| c dir norm | b dir/c dir  1 | 14% |
| b flav exc norm | b/c 0.5 | 28% |
| c flav exc norm |  |  |
| b gluon split norm | 1.40 | 0.19 |
| c gluon split norm | 1.35 | 0.36 |
| Ke norm |  |  |
| K norm |  |  |
| SECVTX scale factor, b | 1.0 | 6% |
| SECVTX scale factor, c | 1.0 | 28% |
| JPB scale factor | 1.0 | 6% |

## Fit results

***2**/DOF=4.6/9*

## b-purity (cross-check)

*l-D**0** **: **126.0 ± 15.5** in the data and   **139.9 ± 15.0** in the simulation*
* **l-**D**±** : **73.7 ± 17.8 **(data)** **and                       **68.5 ± 14.1 **(simulation).*
*J/****: **90.8 ± 10.1 **(data)** **and **101.9 ± 11.4 **(simulation)*
*Ratio of the **b**-purity in the simulation to that in the data is **1.09 ± 0.11** *
*Discrepancy between observed and predicted number of a-jets with SLT tags due to heavy flavor is not due to an underestimate of the bb contribution*

## 2.6 < mee< 3.6 GeV/c2
2.9 < m< 3.3 GeV/c2
SS dileptons (with 10% error) used to estimate and remove bkg. to OS dileptons due to misidentified leptons.
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)

*2.9 < m****< 3.3 GeV/c**2*
*SS dileptons (with 10% error) used to estimate and remove bkg. to OS dileptons due to misidentified leptons.*
*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)*

***b-purity (cross-check)***

## J/ mesons from B-decays

*In generic-jet data we do not have 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 *
*The observed number of SLT tags is 1.2 **** lower than the prediction rather than 50% larger as in the inclusive lepton sample.*

## Data

## Heavy flavors in the simulation are identified at generator level

## 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*
*K**e**  and K****account 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-parameter corr. coeff.

- For

## 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.

## 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*

##  away-jets with SLT tags

-  away-jets with SLT tags