1. Reddy Pratap Gandrajula (University of Iowa) on behalf of CMS
Measurement of 𝝈 𝑩 𝒄 ± ×𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝈 𝑩 ± ×𝑩𝒓 𝑩 ± → 𝑱 𝝍 𝑲 ± and 𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ 𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± at 𝑺 =𝟕 𝑻𝒆𝑽
Reddy Pratap Gandrajula (University of Iowa) on behalf of CMS
Analysis referance:BPH
4/8/2014
APS April meeting 2014

2. 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± , 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ , and 𝑩 ± → 𝑱 𝝍 𝑲 ± signals
Outline
Introduction
CMS detector
Analysis Strategy
𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± , 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ , and 𝑩 ± → 𝑱 𝝍 𝑲 ± signals
Results
Summary and Conclusions
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3. Introduction
LHC opened a new era for the flavor physics by copiously producing heavy flavors at 7 and 8 TeV.
One particle which deserves careful study is the 𝐵 𝑐 meson, whose small cross-section has limited, so far, its experimental investigation.
A rich program of measurements is being carried out by LHCb at 2<η<5; the complementary pseudorapidity region can be accessed by CMS
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4. Introduction….
CMS, with excellent muon identification system and tracker detectors, allows for 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± and 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ final state studies in a central 𝜂 region.
Measurements, driven by the 𝑱 𝝍 in the final state provides basic information about the 𝑩 𝒄 ± meson, which serve an introduction for further experimental investigation. 𝑢 𝑢
𝜋 +
𝜋 + 𝑑 𝑑 𝑏 𝑏
𝐵 𝑐 + 𝑐
𝑱 𝝍
𝐵 𝑐 + 𝑐 𝑐 𝑐 𝑐
𝑱 𝝍 𝑐 g g 𝑑
𝜋 − 𝑢 𝑑
𝜋 + 𝑢
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5. Good performance from LHC & CMS
CMS & LHC
Good performance from LHC & CMS
Identifies and measures 𝑒, 𝜇, 𝛾, charged particles, Jets, etc.
In 2011 it collected 𝑓𝑏 −1 pp data.
Analysis is performed on 5.1 𝑓𝑏 −1 data.
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6. Most important sub-detector elements for this analysis
Slice view of CMS
Most important sub-detector elements for this analysis
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7. Analysis Strategy The analysis is driven by 𝑱 𝝍 reconstruction:
Two oppositely – charged muons selected with the standard muon selection.
All triggers apply the following cuts:
cos 𝛼 >0.9 , where 𝛼 is the pointing angle, in the transverse plane, between the dimuon momentum and the direction from the dimuon vertex to the beam spot.
𝐿 𝑥𝑦 𝜎 𝑥𝑦 >3, where 𝐿 𝑥𝑦 is the transverse detachment between the dimuon vertex and the beamspot and 𝜎 𝑥𝑦 is the corresponding uncertainty.
𝑝 𝑇 𝜇𝜇 >6.9 𝐺𝑒𝑉
Dimuon vertex probability 𝑃 𝑉𝑇𝑋 >0.5%
Distance of closest approach between the two muons < 0.5 cm.
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8. The cuts were tightened with increasing instant.Lumi.
Analysis Strategy…
The cuts were tightened with increasing instant.Lumi.
𝑝 𝑇 𝜇 >4.0 𝐺𝑒𝑉, |𝜂| 𝜇 <2.2, Dimuon vertex probability 𝑃 𝑉𝑇𝑋 >15%
Dimuon trigger matched 𝑑𝑖𝑚𝑢𝑜𝑛 𝑜𝑛𝑙𝑖𝑛𝑒 𝑜𝑓𝑓𝑙𝑖𝑛𝑒 ∆𝑅<0.5
𝐵 𝑐 + → 𝐽 𝜓 𝜋 + 𝐵 𝑐 + → 𝐽 𝜓 𝐾 + candidates: 𝐽 𝜓 with 1 track, assuming that is a pion (kaon)
𝐵 𝑐 + → 𝐽 𝜓 𝜋 + 𝜋 + 𝜋 − candidates: 𝐽 𝜓 with 3 tracks, assuming that they are pions.
primary
vertex
secondary
𝐵 (𝑐) +
𝐾 + 𝜋 +
primary
vertex
secondary
𝐵 𝑐 +
𝜋 −
𝜋 +
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9. Analysis Strategy….. The pion(kaon) candidates are required to have:
a track fit (𝜒 2 𝑛𝑑𝑜𝑓 )<3
Tracker hits>6, pixel hits ≥2, 𝜂 <2.4 and 𝑝 𝑇 >0.9 𝐺𝑒𝑉 𝑐 .
𝐿 3𝐷 𝜋 ± , 𝑱 𝝍 𝜎 3𝐷 <6 (Inferred from MC).
Δ𝑅 𝑱 𝝍 , 𝜋 𝐾 <2.5 for 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± and 𝐵 ± → 𝑱 𝝍 𝑲 ±
In 𝑩 𝒄 + → 𝑱 𝝍 𝝅 + 𝝅 + 𝝅 − analysis, Δ𝑅<1 is required for the highest 𝑝 𝑇 track, while Δ𝑅<1.6 is required for the other two pions.
𝑩 𝒄 + Vertex probability >0.1%; 𝑝 𝑇 ( 𝑱 𝝍 )>7.1 𝐺𝑒𝑉 𝑐 .
In case of multiple 𝑩 𝒄 ± ( 𝐵 ± ) candidates, the one with highest 𝑝 𝑇 is retained.
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10. Requirements for 𝑩 𝒄 + reconstruction and Cut optimization using 𝑺 𝑺+𝑩
𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓
𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± and 𝑩 ± → 𝑱 𝝍 𝑲 ±
𝑝 𝑇 𝐵 𝑐 >15GeV/c;
𝑦 𝐵 𝑐 <1.6;
𝐵 𝑐 Vertex CL>20%;
cos 𝜃 >0.99;
𝑝 𝑇 𝜋 1 >2.5GeV/c;
𝑝 𝑇 𝜋 2 >1.7GeV/c;
𝑝 𝑇 𝜋 3 >0.9GeV/c;
Δ𝑅 𝑱 𝝍 , 𝜋 𝑠 <0.5 where Δ𝑅 is taken from Δ𝜂 and Δ𝜙 derived from the 𝑱 𝝍 momentum vector and the sum of the momentum vectors of the three pions 𝜋 𝑠 .
𝑝 𝑇 𝐵 𝑐 >15GeV/c;
𝑦 𝐵 𝑐 <1.6;
𝐵 𝑐 Vertex CL>6%;
cos 𝜃 >0.9;
𝑝 𝑇 𝜋 >2.7GeV/c;
Δ𝑅 𝑱 𝝍 ,𝜋 <1.
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11. 𝑩 𝒄 + and 𝑩 + mass fits
𝑩 𝒄 ± Signals modeled to a Gaussian fit, 𝑩 + signal to a double Gaussian fit and background is modeled to 2nd order Chebyshev polynomial.
𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ yield:92±27; m:6.266± 𝐺𝑒𝑉 𝑐 2
𝑩 𝒄 + → 𝑱 𝝍 𝝅 + yield:176±19; m:6.267± 𝐺𝑒𝑉 𝑐 2
𝑩 + → 𝑱 𝝍 𝑲 + yield:90398±357; m: ± 𝐺𝑒𝑉 𝑐 2
Bkg 𝑩 𝒄 ± → 𝑱 𝝍 𝑲 ± 𝑲 ∓ 𝝅 ± negligible
Bkg 𝑩 𝒄 ± → 𝑱 𝝍 𝑲 ± negligible
Bkg 𝑩 ± → 𝑱 𝝍 𝝅 ± negligible
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12. The ratio 𝝈 𝑩 𝒄 ± ×𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝈 𝑩 ± ×𝑩𝒓 𝑩 ± → 𝑱 𝝍 𝑲 ± measurement
The ratio can be obtained through the relation:
𝑵 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝑵 𝑩 ± → 𝑱 𝝍 𝑲 ± = 𝝈 𝑩 𝒄 ± ×𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± × 𝝐 𝑩 𝒄 ± 𝝈 𝑩 ± ×𝑩𝒓 𝑩 ± → 𝑱 𝝍 𝑲 ± × 𝝐 𝑩 ± ,
Where N is the number of signal events and 𝜖 𝑩 (𝒄) ± is the overall analysis efficiency for the 𝑩 ± and 𝑩 𝒄 ± reconstruction.
Pt dependent efficiency from MC - BCVEGPY for 𝑩 𝒄 ± and PYTHIA for 𝑩 ±
Data are corrected event-by-event according to their 𝑝 𝑡 and related MC efficiency. The efficiency corrected mass plots for 𝑱 𝝍 𝝅 ± and 𝑱 𝝍 𝐾 ± are shown here.
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13. Substructure Study & Efficiency Parameterization
Data shows some hints of 𝑎 1 ± 1260𝑀𝑒𝑉 and 𝜌 𝑀𝑒𝑉
resonances; but the 𝑩 𝒄 ± yield (about 100) is too small to
perform a detailed Dalitz analysis.
𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ (Dalitz plot representation of five-body
decay of a spinless particle) can be described in its center of
mass by mass-combinations: 𝑚 2 𝜇 + 𝜋 + 𝑙𝑜𝑤 , 𝑚 2 𝜋 + 𝜋 − ℎ𝑖𝑔ℎ , 𝑚 2 𝜇 + 𝜋 − , 𝑚 2 𝜋 + 𝜋 + , 𝑚 2 𝜇 − 𝜋 + 𝑙𝑜𝑤 , 𝑚 2 𝜇 − 𝜋 + ℎ𝑖𝑔ℎ and 𝑚 2 𝜇 − 𝜋 − ; the 𝑙𝑜𝑤 and ℎ𝑖𝑔ℎ
subscripts refers to the lower and higher invariant mass combination where 𝜋 + is
involved. 𝝐=| 𝒑 𝟎 + 𝒑 𝟏 .𝒙+ 𝒑 𝟐 .𝒚+ 𝒑 𝟑 .𝒛+ 𝒑 𝟒 .𝒘+ 𝒑 𝟓 .𝒓+ 𝒑 𝟔 .𝒕+ 𝒑 𝟕 .𝒔|
Where x= 𝑚 2 𝜇 + 𝜋 + 𝑙𝑜𝑤 , y= 𝑚 2 𝜋 + 𝜋 − ℎ𝑖𝑔ℎ , 𝑧=𝑚 2 𝜇 + 𝜋 − , w= 𝑚 2 𝜋 + 𝜋 + , r= 𝑚 2 𝜇 − 𝜋 + 𝑙𝑜𝑤 , t= 𝑚 2 𝜇 − 𝜋 + ℎ𝑖𝑔ℎ , s= 𝑚 2 𝜇 − 𝜋 − ; and 𝑝 𝑖
are the free parameters in the 7th dimensional space.
The resulting efficiency function is used to weight the data
event by event. The efficiency – corrected an unbinned
maximum Likelihood fit on data is shown here.
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14. Systematics
The 𝜎 𝑩 𝒄 ± ×𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝜎 𝑩 ± ×𝐵𝑟 𝑩 ± → 𝑱 𝝍 𝑲 ± Systematic uncertainty
The 𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ 𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± Systematic uncertainty
Split data sample: three triggered periods, pileup samples(1≤𝑃𝑉≤6 and 𝑃𝑉≥7).
Fit variant: Default signal fit a single Gaussian, for syst. Study fit signal to a double Gaussian with widths fixed to MC values, and for bkg by a different order Chebyshev polynomial or exp. function.
MC finite size: MC reweighted 𝑌 𝑩 𝒄 ± and 𝑌 𝐵 ± evaluated through pseudo- experiment studies.
Efficiency binning: Various bin values are tested for both 𝑩 𝒄 ± and 𝐵 ±
Split data sample: No triggered periods(limit stat), pileup samples(1≤𝑃𝑉≤6 and 𝑃𝑉≥7).
Fit variant: No variant w.r.t. signal shape(limit stat) and for bkg by a different order Chebyshev polynomial( from 1st to 3rd ).
MC finite size: MC reweighted 𝑌 𝑩 𝒄 ± evaluated through pseudo- experiment studies.
Efficiency binning: Various bin values are tested for 𝑩 𝒄 ± .
Tracking efficiency: efficiency tracking uncertainty for each pion track of 3.9%.
Big. Syst
Big. Syst
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15. Results:In a rapidity region complementary to LHCb
𝝈 𝑩 𝒄 ± ×𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝈 𝑩 ± ×𝑩𝒓 𝑩 ± → 𝑱 𝝍 𝑲 ± = 𝟎.𝟒𝟖±𝟎.𝟎𝟓 𝒔𝒕𝒂𝒕 ±𝟎.𝟎𝟒 𝒔𝒚𝒔𝒕 𝝉 𝑩 𝒄 × 𝟏𝟎 −𝟐
𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ 𝑩𝒓 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± =2.43±𝟎.𝟕𝟔 𝒔𝒕𝒂𝒕 (𝒔𝒚𝒔𝒕)
+0.05
-0.03
+0.46
-0.44
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16. Summary and conclusions
The analysis of 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± and 𝑩 ± → 𝑱 𝝍 𝑲 ± is presented
CMS 7 TeV data permitted the measurement of the ratio: 𝜎 𝑩 𝒄 ± ×𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝜎 𝑩 ± ×𝐵𝑟 𝑩 ± → 𝑱 𝝍 𝑲 ± in a region complementary to that investigated by LHCb collaboration.
The analysis of 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ also permitted the determination of the ratio: 𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ± 𝝅 ± 𝝅 ∓ 𝐵𝑟 𝑩 𝒄 ± → 𝑱 𝝍 𝝅 ±
Our results are in agreement with LHCb ones.
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17. Questions ?
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18. CMS standard soft Muon selection
Muon track should have at least 1 pixel hit and at least 5 silicon hits.
the normalized c2 of muon track < 1.8.
| 𝑑 𝑥𝑦 | < 3.0 cm.
| 𝑑 𝑧 | < 30.0 cm.
Tracker track matched with at least one muon segment (in any station) in both X and Y coordinates and arbitrated.
Triggers and Data Set:
Data Set: /MuOnia/Run2011A-08Nov2011-v1/AOD, /MuOnia/Run2011B-19Nov2011-v1/AOD
Unprescaled displaced vertex dimuon triggers are considered
HLT paths and Luminosity for the signal samples:
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