2018 Workshop on Physics Analysis

11 Jun 2018, 08:00 → 12 Jun 2018, 18:00 Asia/Shanghai

A415 (IHEP)

This workshop focus on CMS physics results with contributions from CMS Chinese groups. The workshop is hold at IHEP, Beijing. People based at Beijing are invited to participate the workshop at IHEP, and people outside Beijing is encouraged to participate the workshop through Vidyo. Both students and senior researchers are welcomed to participate the workshop. The workshop is free, lunch is provided.

Monday, 11 June

1 MSSM Hbb Run II search

Speaker: Ye Chen (IHEP)

Slides cms_higgs_20180611.pdf

2 Search for single production of vector-like quarks decaying into final states with a Z boson decaying leptonically and a top quark with 2017 data

We present a search for single production of heavy vector like quarks, carried out by the CMS collaboration analyzing LHC pp collisions at 13TeV. The vector like quark is a massive top quark partner that is searched for in a mass range between 0.7 and 1.7 TeV and a width between <1% and 30%. Single production can be dominant over pair production, depending on the mass of the new quark. The search is performed in a variety of final states including boosted topologies that can increase the sensitivity of the analysis.

Speaker: Mr Taozhe Yu (IHEP)

Slides presentation_6-11.pdf

3 Search for the production of an excited bottom quark decaying to tW in proton-proton collisions at √s = 13TeV

We are trying to search b* decaying to a a top quark and a W boson in the lepton+neutrino, bjet and Wjet final state ,in proton-proton collisions at √s = 13 TeV recorded by the CMS experiment at the CERN LHC. Data corresponding to an integrated luminosity of 35.6 fb−1 are used.

Speaker: Na PENG (IHEP)

Slides Bstar.pdf

10:00 Break

4 WV analysis improvements with DeepAK8

Reconstruction and identification of boosted heavy particles (top/W/Z/Higgs) can provide powerful handles for new physics searches at the LHC. DNN-based DeepAK8 tagger was investigated in the WV search. The report includes DNN distribution, DNN control plots, W-tagging, and the uplimit results using alpha method. We also designed a mass-decorrelated DeepAK8 tagger. The results were greatly improved compared with the results of tau21 cut.

Speaker: Mr Cheng Chen (PKU)

Slides DeepAK8.pdf

5 Preliminary results and plan on VVV search

A new model, called Bulk Extra Dimension model, which is is modified by the inclusion of Higgs brane from Bulk Graviton model, leads to novel phenomenology. We consider two cases based on this new model. The process is pp → W_kk →Wφ→WWW. And the main difference between these two cases is the choice of the mass of φ. Besides, the first VVV search based on Bulk Graviton model is also studied, in which the graviton decays to tri-W. Some preliminary results of these three cases will be given in my report.

Speaker: Mr Xudong Lyu (Peking University)

Slides Preliminary_results_and_plan__on_VVV_search_6.11.pdf

6 An Unknown Structure in Double J/psi in pp Collision at 8TeV at CMS

Speaker: Dr Jianguo Bian (IHEP)

Slides djpsi8tev_12June2018.pptx

7 Measurement of the production of a single top quark in association with a W boson in the lepton + jets channel

Speaker: Duncan Leggat (高能所)

Slides 2018-06-11_cmsChina_leggat.pdf

8 SEARCH FOR A HEAVY RESONANCE DECAYING TO A PAIR OF VECTOR BOSONS IN THE LEPTON PLUS MERGED JET FINAL STATE AT 13TeV

A search for a new heavy particle decaying to a pair of vector bosons (WW or WZ) is presented using data from the CMS detector corresponding to an integrated luminosity of $35.9~\mathrm{fb}^{-1}$ collected in proton-proton collisions at a centre-of-mass energy of $13~\mathrm{TeV}$ in 2016. One of the bosons is required to be a W boson decaying to $e\nu$ or $\mu\nu$, while the other boson is required to be reconstructed as a single massive jet with substructure compatible with that of a highly-energetic quark pair from a W or Z boson decay. The search is performed in the resonance mass range between 1.0 and 4.4. The largest deviation from the background-only hypothesis is observed for a mass near $1.4~\mathrm{TeV}$ and corresponds to a local significance of 2.5 standard deviations. The result is interpreted as an upper bound on the resonance production cross section. Comparing the excluded cross section values and the expectations from theoretical calculations in the bulk graviton and heavy vector triplet models, spin-2 WW resonances with mass smaller than $1.07~\mathrm{TeV}$ and spin-1 WZ resonances lighter than $3.05~\mathrm{TeV}$, respectively, are excluded at 95% confidence level.

Speaker: Mr Huang Huang (Peking university)

Slides 2018_analysis_workshop__Huang_Huang__20180611.pdf

9 Higgs measurements and search for a second lighter Higgs boson in the diphoton decay channel

Speaker: Mr Junquan TAO (IHEP/CAS)

Slides ChineseCMSWorkshop_JTaoIHEP.pdf

10 RunII VBS Wgamma analysis

We search for the EWK WGamma+2Jets process predicted in RunII. In our analysis,W produced with a photon and two Jets,W boson dacays to a muon/electron and neutrino and neutrino turns into missing energy.We use MadGraph to model several backgrounds such as QCD WGamma+Jets, TTbar and so on, for fake lepton estimation and fake photon estimation, we use data-driven model.

Speaker: Mr Huang Qianming (PKU)

Slides ihep20180612_qianming.pdf

15:50 Break

11 Search for vector leptoquarks

In the last years, several B physics experiments have measured possible hints of new physics. Leptoquarks provide a simple explanation of these results. We present a possible analysis that is looking for vector leptoquarks at the CMS experiment using the Run II statistics.

Speaker: Aniello Spiezia (高能所)

Slides AnielloSpiezia_CMSWorkshop.pdf

12 Search for an $L_{\mu}-L_{\tau}$ gauge boson using Z$\rightarrow4\mu$ events in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$

Search for a narrow Z$^{\prime}$ gauge boson with a mass between 5 and 70 GeV resulting from an $L_{\mu}-L_{\tau}$ $U(1)^{\prime}$ symmetry would be reported. Theories that predict such a particle have been proposed as an explanation of various experimental anomalies including the lack of a dark matter signal in direct detection experiments, tension in the measurement of the anomalous magnetic moment of the muon, and reports of possible lepton flavour universality violation in B-meson decays. The data sample consists of proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$ collected with the CMS detector at the LHC and corresponds to an integrated luminosity of $77.3~\mathrm{fb}^{-1}$. The search considers events containing four muons with an invariant mass near the Z boson mass, and the selection is further optimized to be sensitive to the Z$^{\prime}$ signal that may be present in Z$\rightarrow4\mu$ decays. The observations are consistent with the standard model predictions. Upper limits of $10^{-8}$--$10^{-7}$ at $95\%$ confidence level are set on the branching fraction $\mathcal{B}(\rm{Z} \rightarrow$Z$^{\prime} \mu \mu) \times \mathcal{B}($Z$^{\prime} \rightarrow\mu \mu)$, which excludes a Z$^{\prime}$ boson coupling strength to muons above 0.004--0.3, depending on the Z$^{\prime}$ mass. These are the first dedicated limits on the $L_{\mu}-L_{\tau}$ model at the LHC

Speaker: Dr Muhammad Ahmad (IHEP)

Slides CMS_WorkShop_Ahmad.pdf

13 Observation of electroweak-induced W^{\pm}W^{\pm}jj production

I will discuss the CMS Collaboration's recently published observation of electroweak-induced W^{\pm}W^{\pm}jj production using the channels in which the W bosons decay to electrons or muons and the 36 fb^{-1} of data collected in 2016 at a center-of-mass energy of 13 TeV. The observed significance is 5.5 standard deviations, compared to an expectation of 5.7 standard deviations. Additionally, the same signal region is used to set limits on anomalous quartic gauge couplings and on the vector boson fusion production cross section times branching ratio to W^{\pm}W^{\pm} of doubly charged Higgs bosons in the Georgi-Macachek model.

Speaker: Andrew Levin (Peking University)

Slides CMS_physics_analysis_workshop_at_IHEP.pdf

Tuesday, 12 June

14 Search for ttH production in multi-lepton final states with CMS 2017 dataset

Speaker: LI Binghuan

Slides 5_TTHLep_Chinese_CMS_Physics_Analysis_12_06_2018_BL.pdf

15 Latest CMS results on heavy resonance search in the dilepton final state

There are several theories beyond the standard model (SM) predicting the existence of new heavy resonances that can couple to quarks or gluons and can decay to dilepton pairs. This talk presents the search for such kind of heavy resonances in electron-electron final state, muon-muon final state and electron-muon final state separately with the latest data collected by CMS. No evidence for physics beyond the Standard Model is observed in the invariant mass spectrum of selected di-lepton events. The 95% CL observed lower limits on the masses of different models are set.

Speaker: Xuyang Gao (B)

Slides 2018-06-04_Xuyang.pdf

16 Tag and Probe studies for muon efficiencies and scale factors measurements with 2016 and 2017 data & MC

One of the most important aspect in every analysis is the optimisation of the event selection. The ideal selection would efficiently eliminate the background events while keeping the signal rates untouched. Since every real selection affects signal efficiencies also, this effect has to be studied and quantified. These efficiencies can be extracted directly from the simulation, but there is a danger such as bias which can appear because of insufficient event description and the lack of understanding of the detector. Mitigating the bias from MC is achieved by measuring the selection efficiencies directly from the experimental data using the Tag-and-Probe (TnP) method. In the case of muon efficiency measurements, this method exploits Z and J/ψ events to estimate the reconstruction and selection efficiencies. We measure efficiencies and scale factors (SFs) pertaining to muon identification, isolation and requirement on impact parameter with 2017 rereco data recorded with CMS detector of LHC. Individual SFs are then combined to get final muon SFs. We also validate TnP studies with 2016 data and MC. We find that muon selection efficiency results are good. The overall scale factors are typically ~0.99. The uncertainties are ~1% per muon.

Speaker: Mr TAHIR JAVAID (IHEP, CAS)

Slides mu_T&P_tahir_IHEP_12.06.2018.pdf

10:30 Break

17 rare decays and LU test

Speaker: Dayong Wang (Peking University)

Slides CMSChina_20180612_wangdy.pdf

18 Angular analysis of B+->K+mumu and B+->K*+mumu

Speaker: Mr Geng Chen (Peking U.)

Slides CMS_angular_analyses_2018_06_12.pdf

19 angular analysis of B0->K*0 mu mu

Angular analyses of penguin B hadron decays such as B0->K* ll constitute one of the main indirect probes of new physics at LHC, due to the clean theoretical predictions and precise experimental results that can be obtained. In this report we present the most recent results of the CMS experiment on this subject, including the measurement of the P1 and P5’ angular variables in B0->K*mumu decays.

Speaker: Ms linwei li (Peking University)

Slides workshop_llw.pdf

20 Study of the underlying event in top quark pair production in pp collisions at 13 TeV and underlying event tunes with high order parton distribution functions

Normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event are measured in top quark and antiquark pair events produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis is based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 inv-fb. The selected events contain one electron, one muon, and two jets from the hadronization and fragmentation of b quarks. These measurements characterize, for the first time, the properties of the underlying event in events with top quarks and confirm its uni- versality at energy scales typically above twice the top quark mass. Studies of underlying event using high order parton distribution function sets are also presented. For the first time, it is shown that predictions obtained with tunes based on higher-order PDF sets are able to give a reliable description of minimum bias and underlying event measurements, with a similar level of agreement as predictions from tines using leading order parton distribution function sets.

Speaker: Dr Efe Yazgan (高能所)

Slides efe_yazgan_china_analysis_workshop_2018.pdf

21 Deep Neural Networks in the ttH multilepton analysis

Speaker: Joshuha Thomas-Wilsker (高能所)

Slides CMSChina-ttHMultilepton-DNN.pdf

22 search for EWK ZA+2jets with 2016 data in CMS

EWK ZAjj production is precisely predicted by the SM, and anomalous quartic coupling is a probe to the physics beyond SM. ZAjj obtained first evidence of VBS process with RunI data, First 5𝜎 measurement of VBS di-boson process has been obtained in ssWW channel with 2016 data. we aim to obtain another VBS discovery with 2016 data in EWK ZAjj, and we are reaching pre-approve now.

Speaker: meng lu (Peking University)

Slides Search_for_Electroweak_ZAjj_with_2016_data_on_CMS.pdf

15:50 Break

23 Measurement of the differential cross section of Z boson production in association with jets at CMS

The measurement of the differential cross section of Z boson production in association with jets (Z+jets) in proton-proton collision at the center-of-mass energy of 13 TeV will be present. The data has been recorded with the CMS detector at the LHC during the year 2015, corresponding to an integrated luminosity of 2.19 fb−1. The goal of analysis is to perform a first measurement at 13 TeV of the cross sections of Z+jets as a function of the jet multiplicity, its dependence on the transverse momentum of the Z boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, and the balance in the transverse momentum between the reconstructed jet recoil and the Z boson. The results are obtained by correcting the detector effects, and are unfolded to particle level. The measurement are compared to four predictions using different approximations: at the leading-order (LO), next-to-leading-order (NLO) and next-to-next-to-leading order (NNLO) accuracy. The first two calculations used {\sc MadGraph5_aMC@NLO} interfaced with {\sc pythia8} for the parton showering and hadronisation, one of which includes matrix elements (MEs) at LO, another includes one-loop corrections (NLO). The third is a fixed-order calculation with NNLO accuracy for Z+1 jet using the N-jettiness subtraction scheme (Njetti). The fourth uses the {\sc geneva} program with an NNLO calculation combined with higher-order resummation. Key words: physics, CMS, standard model, Quantum Chromodynamics, cross section, Z boson, jets, {\sc MadGraph5_aMC@NLO}, {\sc geneva}

Speaker: Qun WANG (Peking University)

Slides talk_cms_IHEP_12June.pdf

24 Feasibility study and future plan of search for low mass higgs boson with mass < 125 GeV

Speaker: Ms Sijing Zhang (CMS)

25 Deep Learning with Matrix Element Method on ttZ at CMS

Speaker: JUNHO LEE (school of physics Peking Uniersity)

Slides Presentation_IHEP.pdf