Bachelor project (experimental CMS): (or parts as internship/summer student project)

Combined Z to two lepton and Higgs to four lepton distributions from CMS and ATLAS (Open) Data

Abstract/Physics motivation:

Higgs to four lepton distributions from CMS Run I Open Data, and Z to two lepton distributions from both CMS and ATLAS Open Data were already studied in previous (summer student) projects. All relevant Higgs data from both Run 1 and Run 2 have already been published by both collaborations. ATLAS has recently released the full 2016 subset of their two- and four-lepton data for educational purposes, sufficiently detailed for the purpose of this project. CMS has recently significantly extended its full research grade Open Data sets, about doubling the available statistics. More will be released by the ned of 2023. For CMS-internal purposes, the full statistics of all Run 1 and Run 2 data sets is available. Producing combined two- and four-lepton mass distributions from CMS and ATLAS, adapting the already existing tools to all available Open Data statistics, will set benchmarks for potential common analysis of CMS and ATLAS Open Data. For LHCb, corresponding dilepton data are also available since end of 2022. Adding all the available not yet open CMS data can yield Z and Higgs distributions with the highest statistics ever produced (for internal purposes until either the data are released or the collaborations agree to make the plots public). The results will also be used for the benchmarking of the respective detector resolutions and for the validation of alignment calibration studies.

Short description of the project the student should work on:

Two- and four-lepton spectra with nanoAOD and nanoAODplus,
possibly with associated charm production, including CMS, ATLAS and LHCb Open Data

Physics / Computing/ Engineering Content of the project :

Insights into electroweak physics and QCD;
The world's highest statistics Higgs and Z mass distributions;
The world's only public Higgs and Z mass distributions from more than one experiment;
Learning/working with ROOT and C++;
validation of nanoAODplus and nATLASAOD;
comparison of detector resolutions;
Bonus: Search for Z+J/psi, Z+Upsilon, H->ZZ*->Z+J/psi, H->ZZ*->Z+Upsilon
(technically member of CMS collaboration)

Special Qualifications expected from the student:

No previous knowledge necessary. Previous knowledge of ROOT, C++, linux as well as basic knowledge of particle and/or detector physics would be an advantage.

workflow of the project (3 months, up to 5 months if courses are still followed in parallel):

revive the existing tools from the 2019-2022 summer student projects

rerun them over the latest version of the CMS Open Data sets

finalise the adaptation to the latest ATLAS Open Data release and run them over the corresponding datasets

run over additional CMS Open Data sets as they come in

produce combined public plots

run over additional internal CMS datasets (DoubleMuon and DoubleElectron 2015, 2016-2018 UL), adjust cuts to Run 2 analysis

produce combined internal plots

write bachelor thesis

Physics skills needed:

familiarity with basic notions of particle physics

affinitity to experimental and technical methods

Computing skills needed:

basic familiarity with linux, willingness to learn ROOT/C++

DESY co-supervisor: Achim Geiser (also Privatdozent Uni-HH) + co-supervision by PhD student
University co-supervisor: to be determined

Time scale: any time from January 2023

Presence at DESY during the project: between 30% and 100%, depending upon arrangement

Bachelor or Master project (experimental ZEUS): (or parts as internship or summer student project)

J/psi and D meson production in ZEUS, CMS, LHCb and ALICE (Open) Data

Abstract/Physics motivation:

The study of open and hidden charm production in ep and pp collisions is one of the means to understand Quantum Chromodynamics (QCD) at the boundary of the perturbative and nonperturbative regimes.
Charm production in ep photoproduction and pp hadroproduction should be closely related, but should also exhibit some notable differences. Both the ZEUS common ntuples and the CMS nanoAODplus ntuples contain muons from J/psi decays and charm mesons in similar formats which can straightforwardly be translated into each other. Doing such a translation allows a common analysis and direct comparison of the resulting distributions with the same analysis code. For D mesons from LHCb Open Data such an interface already exists. For D mesons from ALICE Open Data it would have to be set up from scratch.
The first (simpler) goal is to extend the partially already existing tools to be able to read the ZEUS, CMS and LHCb (possibly also ALICE) data with the same code, to use these tools to produce corresponding kinematic distributions, and to draw conclusions from their comparison at reconstruction level.
The second goal (for the master variant, or an excellent bachelor student) is to add simulations where available (i.e. for ZEUS and CMS), calculate efficiencies, derive corresponding cross sections, and discuss what one can learn from these concerning QCD. Depending on the outcome, the result could serve as a starting point for a separate full PhD thesis on the research grade ZEUS and CMS data.

Short description of the project the student should work on:

Further development of nanoCNZeus and comparison of dilepton and D meson spectra between ZEUS and CMS, including CMS, LHCb and possibly ALICE Open Data

Physics / Computing/ Engineering Content of the project:

Insights into QCD physics and heavy flavour production;
Learning/working with ROOT and C++;
Development and validation of nanoCNZEUS;
First ever combined analysis of HERA and LHC data at reconstructions level
(technically member of ZEUS collaboration)

Goal for output:

bachelor or master thesis;
public Open Data analysis example in the context of PUNCH4NFDI;
report at conferences;
possibly contribution to publication

Special Qualifications expected from the student:

No previous knowledge necessary (learning on the job).
Some previous knowledge of ROOT, C++, linux as well as basic knowledge of particle and/or detector physics would be an advantage.
Travel to/stay at DESY for external student might be negotiable.

DESY co-supervisor: Achim Geiser (also Privatdozent Uni-HH) + co-supervision by PhD student
University co-supervisor: to be determined

Time scale: any time from January 2023

Master project (experimental CMS): (already allocated in collaboration with Perugia)

Measurement of the total cross section for charm production in pp interactions at 900 GeV with CMS

Abstract/physics motivation:

Measurements of the total charm cross section at 5, 7 and 13 TeV are ongoing in CMS. Besides the measurements themselves, the goal is to extract constraints on the charm mass, on PDFs, and on other QCD parameters through the comparison with NNLO QCD predictions from the sqrt(s) dependence. The cross section at 900 GeV has never been measured at any experiment and would strongly extend the lever arm of the theory comparison.

content of the project:

bachelor (3 months, up to 5 months if courses are still followed in parallel) or master (first two months):

set up working environment

run the existing ntuple producer over the existing 900 GeV CMS datasets (Open Data) following existing workflows

run the existing ntuple producer over the existing 900 GeV charm MC (local at DESY) following existing workflows

adjust the existing ntuple analyzer to the 900 GeV requirements

run the ntuple analyzer over the 900 GeV data ntuples with existing workflows

run the ntuple analyzer over the 900 GeV MC ntuples with existing workflows

adapt the existing 7 TeV cross section extraction code to 900 GeV

extract the 900 GeV cross sections (central value) in appropriate binning and compare to the PYTHIA MC predictions

write bachelor thesis if bachelor project (1 month)

master only (further four months) (or excellent bachelor student)

run the FONLL predictions for these cross sections via the FONLL web interface and compare them to the data cross sections

repeat/rerun some of the 7 TeV systematics studies for 900 GeV

contribute to a publication of the 900 GeV results (possibly combined paper with 7 TeV, depending on time scale)

investigate impact of the 900 GeV data point on the extraction of the QCD parameters

write master thesis

Physics skill needed:

familiarity with basic notions of particle physics (bachelor), particle physics course (master)

affinity to experimental methods

some affinity to theory helpful

Computing skills needed:

basic familiarity with linux

output goal:

bachelor or master thesis

contribution to CMS physics paper (e.g. addendum to 7 TeV result, or standalone paper)

DESY co-supervisor: Achim Geiser (also Privatdozent Uni-HH) + co-supervision by PhD student
University co-supervisor: to be determined

Time scale: project already allocated

Presence at DESY during the project: between 30% and 100%, depending upon arrangement; or external cosupervision.

Bachelor or Master project (phenomenology):

Extraction of the total cross section for charm production in pp interactions at 5 TeV from ALICE, CMS and LHCb cross section measurements

Abstract/Physics motivation:

ALICE, CMS and LHCb have published single (ALICE,CMS) and double (LHCb) differential measurements of charm production in pp interactions at 5 TeV. An extension of the CMS measurement to double differential cross sections is ongoing but not yet public. No ATLAS measurements exist so far. The goal in the context of the ongoing HonexComb project (project for the combination of cross sections from all four LHC experiments in the fields of QCD and heavy ion physics) is to combine the kinematic ranges of the already published results from the three experiments and interpolate/extrapolate them to a common total cross section in pp interactions at 5 TeV. If the ongoing new CMS result will be ready in time it should also be included.

workflow of the project:

bachelor (3 months, up to 5 months if courses are still followed in parallel) or master (first two months):

set up working environment

get numerical information of all relevant measurements

provide FONLL predictions for the various existing measurements with a common parameter setup (through the web interface)

provide FONLL predictions for the regions not covered by any measurement

compare to existing data and extract/extrapolate total cross section

write bachelor thesis (1 month)

master (further four months)

determine/extract correlations between different experimental uncertainties, both between data points of same experiment and between experiments

interface FONLL predictions to PDFs other than those provided on the web interface and run predictions

determine systematic uncertainties of extrapolation in unmeasured regions

extract total cross section with full experimental and theoretical uncertainties

write master thesis

Physics skill needed:

familiarity with basic notions of particle physics (bachelor), particle physics course (master)

some affinity to both theory and experiment Computing skills needed:

basic familiarity with linux (C++: learning on the job)

Goal for output:

bachelor or master thesis;
possibly contribution to HonexComb publication

DESY co-supervisor: Achim Geiser (also Privatdozent Uni-HH) + support by PhD student
University co-supervisor: to be determined

Time scale: any time from January 2023, the earlier the better

Presence at DESY during the project: between 30% and 100%, depending upon arrangement

Master or PhD project:

Associated Z+D meson production in pp collisions at CMS

Master or PhD project:

beauty production near threshold in CMS

PhD project (already allocated, 7 TeV close to completion; 13 TeV part might need follow-up; 13.6 TeV part (Run 3) would be new):

Measurement of differential and total charm cross sections in CMS

Master or PhD project (building upon earlier project):

Measurement of differential and total beauty cross sections in CMS

PhD project (already allocated/close to completion):

Measurement of inclusive Jet cross sections in DIS with ZEUS and determination of the strong coupling constant.

PhD project (already allocated, will partially need follow-up):

charm production and study of charm fragmentation in CMS

Other ideas for potential projects (actual projects still to be formulated):

Generate inclusive 4 muon, 2 muon + 2 electron, and 4 electron mass spectra (isolated and nonisolated high quality muons, isolated low quality muons, isolated electrons, primary and detached)

Look for W -> Z* + W* -> mumu +D(*)(s); H -> Z+Z* -> Z + J/psi or Upsilon; Ds ->phi pi -> mumu pi; eta_c -> phiphi-> mumuKK;

Feasability study of a search for the B+L-violating "EW instanton" process p+p -> e+ + mu+ + D0bar + D0bar + K0

Look for QCD sphaleron (ddbar+uubar+ssbar mass ~ 3 GeV) in CMS+Totem data (tagged proton)? (E Shuryak); also eta_c -> ddbar+uubar+ssbar -> KKpi, pipieta, pipieta', hep-ph/0008048; note m(ddbar+uubar+ssbar) ~ 2mrho+mphi+ a bit? thus m(ddbar+uubar+ssbar+ccbar) ~ 2mrho + mphi + mpsi ~ 7 GeV? D+Dbar+K+Kbar; m(ddbar+uubar+ssbar+ccbar+bbbar) ~ 20 GeV? B + Bbar + D + Dbar + pi; look for J/psi+Dstar+mu+X? (Omega_bcc?)