Contact
Name
Roberto Castello
Position
Former member
Postdoc in CP3 from October 2011 to April 2015
Projects
I am involved in the following research directions:

CMS Tracker commissioning and performance assessment

The CMS silicon strip tracker is the largest device of its type ever built. There are 24244 single-sided micro-strip sensors covering an active area of 198m2.
Physics performance of the detector are being constantly assessed and optimized as new data comes.
Members of UCL are playing a major role in the understanding of the silicon strip tracker and in the maintenance and development of the local reconstruction code.

External collaborators: CMS tracker collaboration.

Search for Higgs boson(s) in CMS at the LHC in the llbb topology

Search for Higgs boson(s) within the Standard Model and beyond and also withing a minimal extension of the scalar sector (2HDM).

The final state under study is a Z decaying into a lepton pair associated with two b-jets. This topology is sensitive to a light SM Higgs via the associate ZH production, as well as a middle mass range SM Higgs boson via the inclusive Higgs production followed by its decay into ZZ with one Z decaying into a lepton pair and the other into bbar.

It is also very sensitive to the production of a non standard heavy Higgs boson decaying into Z plus A (pseudo scalar Higgs boson).

Similar selection (but outside of the Z window) is also sensitive to H->aa->llbb, with "a" a generic light scalar.

External collaborators: CMS collaboration.

Past projects
Hide past projects.

I am involved in the following research directions:

Advanced Techniques for Fast Simulation and Data Analysis in High Energy Physics (ASAP)

The discovery of the 125GeV Higgs boson by the LHC experiments has finally opened a new era in the exploration of the TeV scale. The physics programs of CMS and ATLAS aim far beyond the simple discovery, and vigorously pursue the full characterization of the newly discovered state and the full exploration of the TeV scale in search of new phenomena. A key lesson drawn from first two years of LHC running is that most probably first discoveries and then identification of new states/interactions will not be easy. On the one hand, model-independent searches in simple topologies such as single/multi lepton at high transverse momenta have not shown any hint of new physics so far. On the other, topologies with jets and/or missing transverse energies, much more challenging experimentally, do strongly depend on the underlying theoretical models so that efficiently identifying signal enhanced regions of the phase space is quite involved. In this context, multi-variate techniques have become more and more central in the analysis of data from hadron collider experiments, to maximally exploit the information available on the signal and on the backgrounds. Amongst the most advanced techniques and certainly the most powerful one from the theoretical point of view, the so called matrix element method stands out. The main goal of this proposal is to advance the use and the scope of the matrix-element method so to significantly extend the range of physics applications at the LHC to the search of new physics. First we aim at providing the experimental HEP community with complete and automatic simulation tools, such as MadWeight/MoMEMta and Delphes, that overcome the technical limitations of the method. Second we propose to test and apply the new tools to current analyses in signatures that involve final state leptons and b-jets. Finally, we explore new and original applications of the method to both model-dependent or model-independent searches of new physics at the LHC.

External collaborators: CMS collaboration.

Measurement of the b(b)Z process at LHC

At LHC, the Z boson can be produced in association with one or two b-quarks, which is here refereed as b(b)Z production. This process has been seen for the first time at LHC, and measurement of it is an important test of QCD calculations.

For the first time, we observed the Z+b final state and measured of the Z+b/Z+j cross-section ratio in 35.9/pb of pp collisions at 7 TeV, using particle flow jets and simple secondary vertex b-tagging algorithm in the definition of the signal.Emphasis is put on kinematic properties of the jets. With more luminosity, we are working on the measurement of the cross-section for the b(b)Z process, with the identification of one or two b-jets.

External collaborators: A.Gilbert, A.-M.Magnan, A.Nikitenko (Imperial College London); N.Heracleous, A.Perieanu (RWTH Aachen); M.Musich, E.Migliore (University of Torino), and CMS Collaboration.

Publications in CP3
All my publications on Inspire

2016

Search for Neutral Resonances Decaying into a Z Boson and a Pair of b Jets or Tau Leptons
CMS collaboration
[Abstract] [PDF] [Journal] [Full text] Published in Phys. Lett. B 759 (2016) 369
Refereed paper. 28th April.
Summary results of high mass BSM Higgs searches using CMS run-I data
CMS Collaboration
[Full text] CMS Physics Analysis Summary CMS-PAS-HIG-16-007,
Public experimental note. 22nd April.

2015

Search for H/A decaying into Z and A/H, with Z-->ll and A/H-->bb or A/H-->tau tau
CMS Collaboration
[Full text] CMS-PAS-HIG-15-001
Public experimental note. 1st December.

2014

Generic search for a Two Higgs Doublet Model in the Z(ll)+bb final state
R. Castello, A. Caudron, C. Delaere, T.A. du Pree, A. Mertens
[Full text] CMS AN-2014/029
Restricted access (CMS internal analysis note)

Private experimental note. 24th November.
Associated production of heavy flavour final state and a vector boson and search for H->bb
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Higgs properties with CMS
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Alignment and calibration of CMS detector during collisions at LHC
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Data preparation for the Compact Muon Solenoid experiment
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Alignment procedures for the CMS Silicon Tracker detector during pp collisions
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Associated production of W and Z bosons with jets from light and heavy quarks
Roberto Castello on behalf of CMS collaboration
[Full text]
Contribution to proceedings. 4th July.
Evidence for the direct decay of the 125 GeV Higgs boson to fermions
Chatrchyan, Serguei and others
[Abstract] [PDF] [Journal] Subjects: High Energy Physics - Experiment (hep-ex)
Journal reference: Nature Physics 10 (2014) 557
DOI: 10.1038/nphys3005
Report number: CMS-HIG-13-033, CERN-PH-EP-2014-004

Refereed paper. 1st July.
Alignment of the CMS tracker with LHC and cosmic ray data
The CMS collaboration
[Full text] Published on Journal of Instrumentation
Refereed paper. 19th June.
Measurement of the production cross sections for a Z boson and one or more b jets in pp collisions at $sqrt{s}$ = 7 TeV
Chatrchyan, Serguei and others
[Abstract] [PDF] [Journal] [Full text] Published in JHEP 1406 (2014) 120
Refereed paper. 10th February.

2013

Measurement of the production cross sections of a Z boson in association with b jets in pp collisions at sqrt(s) = 7 TeV
The CMS Collaboration
[Full text] First presented at DIS 2013
Public experimental note. 26th August.
Measurement of the cross section of the production of a Z boson in association with 1, 2, or more b jets at CMS in pp collisions at sqrt(s)=7 TeV.
Tristan du Pree, Roberto Castello, Ludivine Ceard, Anne-Marie Magnan, Andrew Gilbert, Christophe Delaere, Adrien Caudron, Jerome de Favereau
[Full text] CMS internal document supporting CMS-SMP-13-004
Private experimental note. 26th August.
Search for Z(ll)H(bb) using Matrix Element method
A.Pin, T. du Pree, R. Castello, J. Vizan C. Beluffi, A. Caudron, C. Delaere, V. Lemaitre
[Full text] Internal CMS analysis note
Private experimental note. 26th August.

2012

Measurement of the Z/gamma* + bb-jets cross section in pp collisions at sqrt(s) = 7 TeV with the CMS detector
The CMS Collaboration
[Full text] First presented at Moriond 2012
Public experimental note. 23rd May.
Measurement of the Z(ll)+bb cross section at CMS
R. Castello, L. Ceard, C. Delaere, A. Pin, and T.A. du Pree
[Full text] CMS internal document supporting CMS-SMP-12-003
Private experimental note. 23rd May.
Measurement of the Z/gamma*+b-jet cross section in pp collisions at 7 TeV
Chatrchyan, SergueiProg. Part. Nucl. Phys. and others
[Abstract] [PDF] [Journal] [Full text] Published in the Journal of High Energy Physics
Refereed paper. 10th April.
Observation of Z+b
The CMS Collaboration
[Full text] Presented first at Moriond 2011
Public experimental note. 9th February.
Leptons efficiency and jets selection for the measurement of Z+b-jet (Z->ll) cross section
R. Castello, L. Ceard, C. Delaere, T.A. Du Pree, A. Gilbert, N.Heracleous, A.M. Magnan
[Full text] Restricted access: CMS internal document supporting CMS paper EWK-11-012
Private experimental note. 9th February.
Aspects of the Z+b cross-section measurement related to b-jet reconstruction
R. Castello, L. Ceard, C. Delaere, T.A. du Pree, A. Gilbert, J. Hauk, N. Heracleous, A.-M. Magnan, E. Migliore, M. Musich, and A. Nikitenko
[Full text] Restricted access: CMS internal document supporting CMS paper EWK-11-012
Private experimental note. 9th February.


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