## CP3 News Blog

all | frontpage | public sidebar

On Monday, 18th of September, at the 10th International Workshop on Top Quark Physics, TOP 2017, in Braga, Portugal, the CMS experiment reported the first observation of the top pair (tt) production using proton-nucleus collisions at 8.16 TeV center-of-mass (c.o.m) energy. The excess of events with respect to the background-only hypothesis corresponds to a significance of more than 5σ (the conventional “golden standard” for observation) even under the most conservative assumptions. The measured top-pair cross section is consistent with the expectations from the scaled proton-proton data as well as pQCD predictions at next-to-next-to-leading order with next-to-next-to-leading-log accuracy.
By Georgios Konstantinos Krintiras on September 18, 2017
On Tuesday, 4th of April, at the 25th DIS international workshop in Birmingham, UK, the CMS experiment extended the very first cross section measurement of the top pair (tt) production at 5.02 TeV center-of-mass (c.o.m) energy. The measurement tracks the evolution of the tt cross section as a function of c.o.m energy, crucial for the extraction of the top-quark pole mass, while it is found to constrain the gluon distribution function at the un-explored large longitudinal parton momentum fraction regime. Future measurements of the tt cross section in nuclear collisions at the same nucleon-nucleon c.o.m energy would profit from the availability of such a reference measurement in pp collisions, without the need to extrapolate from measurements at different c.o.m energies.
By Georgios Konstantinos Krintiras on April 4, 2017
The CP3 department hosted the 2nd CMS HH workshop, on December 8-9th. The meeting was intended to review the status of the current and future HH searches in CMS. An open session was devoted to discussion of the HH theory aspects with a very active participation of the CP3 pheno community. Thanks to all involved for the productive discussions.

The local organizers.
By Miguel Vidal Marono on December 12, 2016
Earlier today, at the 128th LHCC Open session meeting, both ATLAS and CMS experiments demonstrated for the first time candidate events whose signatures are compatible with the decay of a pair of top quarks in the nuclear environment of proton-Lead (pPb) collisions at a center-of-mass energy of 8.16 TeV. Currently, and while steadily moving to the last beam dumps for 2016 (Monday 5th), LHC runs with beam reversal mode at the same center-of-mass energy, where the directions of p and Pb bunches are reversed since not all LHC experiments are symmetric.
By Georgios Konstantinos Krintiras on November 30, 2016
Our CP3 colleague Marco Musich has been awarded an "achievement award" by the CMS Collaboration "For his outstanding contributions to the Alignment and Calibration group."
By Giacomo Bruno on November 23, 2016
CERN just launched "In Practice", a series of articles about experimental physicists working on CERN experiments. Our colleague and friend Abideh (Nadjieh) Jafari is one of the first people they met, in the "CP3 office" at CERN. Enjoy the reading!
By Andrea Giammanco on November 15, 2016
An important milestone has been accomplished by NA62 collaboration with the completion of the three Gigatracker stations. As it can be seen in the picture, high intensity SPS beam can be fully tracked by NA62 with a time resolution of <200 ps. This installation is essential to fully exploit the capabilities of NA62 and opens the door to a 10% measurement of the very rare decay $K^+\to\pi^+\nu\bar{\nu}$<\latex>
By Eduardo Cortina Gil on October 2, 2016
CP3 member Matthias Komm won today the first prize for the poster competition at the 9th International Workshop on Top Quark Physics, where he presented his recent work. Congratulations!
By Andrea Giammanco on September 21, 2016
On Thursday, 16th of June, at the LHCP international conference in Lund, Sweden, the CMS experiment presented the very first cross section measurement of the top pair (tt) production at 5.02 TeV center-of-mass (c.o.m) energy. The measurement tracks the evolution of the tt cross section as a function of c.o.m energy, crucial for the extraction of the top-quark pole mass, while it can be used to constrain the gluon distribution function at the un-explored large longitudinal parton momentum fraction regime. Future measurements of the tt cross section in nuclear collisions at the same nucleon-nucleon c.o.m energy would profit from the availability of such a reference measurement in pp collisions, without the need to extrapolate from measurements at different c.o.m energies.
By Georgios Konstantinos Krintiras on June 16, 2016
Dear Matrix Element Method enthusiasts, we are happy to announce the release of MoMEMta. In our web page you will find direct links to the GitHub repository, instructions on how to install and run MoMEMta, technical documentation, and many other things. If you are interested, please try it!! We are waiting for your feedback

MoMEMta is a CP3 product, adapting the MadWeight philosophy to the experimental needs.

The MoMEMta team
By Miguel Vidal Marono on June 2, 2016
As reported today in the UCLouvain portal, a new line of research has started in CP3, bridging observational cosmology and particle physics. Thanks to a grant financed by INNOVIRIS, Chiara Arina will lead a team of young researchers towards new promising directions in clarifying the nature of Dark Matter.
By Fabio Maltoni on December 9, 2015
Thursday, October 29, 2015 at 20:30 at Cinema Park, Montigny street in Charleroi

Imagine yourself as Edison when his first light bulb went lit or Franklin when he received his first shot of electricity: "The Particle Fever" allows the general public to be at the forefront of the most important and most incredible scientific adventure of all time.
The film follows six in the privacy brilliant scientists trying to unravel the mysteries of the Universe. Through their successes and failures, we discover the most important and fascinating scientific advance of the world towards the infinitely small.
10,000 scientists from over 100 countries have joined forces in pursuit of one goal: recreate the conditions that existed just moments after the Big Bang. In Belgium, there are nearly 150 people involved, including more than 30 from CP3.
By Christophe Delaere on September 26, 2015
On Tuesday, 15 September, at the TOP2015 international workshop in Ischia, Italy [1], the CMS experiment presented the first cross section measurement of the electroweakly-produced top quark at 13 TeV c.o.m energy.
"I think everyone must have been completely and thoroughly impressed. This must be by far the most complex thing that CMS has done so far on 13 TeV", said Andreas Meyer, one of the leaders of top quark analysis group in CMS.
By Abideh Jafari on September 17, 2015
In occasion of the EPS-HEP conference, to demonstrate the good performance of the detector at the Run-II start-up, the CMS collaboration has released the first illustrative event displays and distributions of observables designed to study top-quark events. The data set consists of the first 41 inverse picobarns of proton-proton collisions recorded by the CMS detector at a center-of-mass energy of 13 TeV with a magnetic field of 3.8 Tesla in the solenoid, during the LHC development run with a bunch spacing of 50 ns that took place in July 2015. Although the first quantitative statements will only be released later, these very early data already demonstrate unambiguous presence of the top-quark pair signal (also confirmed at the same conference by the ATLAS collaboration with 6 inverse picobarns) and early hints of single top. CP3 members are involved in these early studies.
By Andrea Giammanco on July 24, 2015
On Wednesday 24, the CP3 council has elected Fabio Maltoni has our new CP3 director. He will start his mandate in september 2015 for a period of three years. Congratulation!
By Vincent Lemaitre on June 25, 2015
Claude Duhr and collaborators have provided predictions for the QCD production cross section of a Higgs boson at the LHC at an unprecedented accuracy. This result is the most difficult (N3LO) computation for such an observable ever made. The theoretical uncertainty on the production cross section has reduced by a factor of two, an important step towards a precise determination of the properties of the newly discovered scalar boson.
By Fabio Maltoni on March 27, 2015
Editor's suggestion of the Physical Review Letters features CP3's research in Cosmology. J. Martin, C. Ringeval and V. Vennin work shows that the current Cosmic Microwave Background measurements by the Planck satellite can be used to learn about the so-called reheating era; the first epoch at which the Universe acquired a (very hot) temperature.
By Christophe Ringeval on February 27, 2015
On February 9th CMS celebrated a total of 28 CMS members who received the CMS achievement award, in special recognition for their contributions to the CMS experiment.

Dr. Jonathan Jason Hollar (Université Catholique de Louvain) was one of them, “For his outstanding contributions to the CT-PPS TDR, particularly the feasibility study on the measurement of exclusive WW production.”
By Christophe Delaere on February 20, 2015
CP3 recently acquired a MakerBot Replicator 2, a 3D printer capable of building plastic objects up to 15x15x25cm with a precision of 0.1mm. 3D printing is more and more used in experimental physics, and was already used at the CRC earlier this year. Now we will be able to prototype and design new pieces ourself, for outreach and research.
By Jérôme de Favereau on December 9, 2014
One of the most praised aspects of working at CP3 is the strong interaction between the local theorists and experimentalists. A very recent example of that is the search for single top + Higgs in the H->bb decay channel, which was studied in depth at CP3 from the phenomenological point of view in [1], and searched in 20/fb of CMS data collected in 2012 at a center-of-mass energy of 8 TeV as reported in [2].
By Andrea Giammanco on October 9, 2014
For the first time, the Z+b-jets process has been measured as a function of the b-jet multiplicity. In line with the spirit of CP3, the analysis benefited from direct interaction between experimentalists and phenomenologists, and members of CP3 have significantly contributed to this study, e.g. to the identification of b jets, as well as the background estimates using MadWeight. The CMS measurements are used to test various predictions from event generators, a.o. MadGraph and aMC@NLO, that both have been partially developed at CP3, and data favour the predictions in the five-flavour scheme, where b quarks are assumed massless. Furthermore, kinematic properties of the reconstructed particles in the Z+bb final state are tested, which is of interest for studies of the H-boson in the H->bb decay, as well as in searches for extensions of the Standard Model.
By Tristan du Pree on July 7, 2014
Physics Review Letters just accepted for publication the paper documenting the discovery by CMS (with CP3 contribution) of a new electro-weak process of production of single top quarks in hadron collisions, in which a top quark is accompanied by an on-shell W boson.
By Andrea Giammanco on April 17, 2014
The latest results of the CMS search for massive, long-lived, charged particles at the LHC, which is led and mainly performed by CP3 members, entered the last issue of the CERN courier (April 2014 Volume 54 Issue 3).
By Loïc Quertenmont on April 10, 2014
The offshell production of the higgs was used to set indirect constraints on the 125GeV higgs boson width. The ZZ->4l and ZZ->2l2v channels were used for this analysis. These important results have been highlighted yesterday as the "hot-topic" of the Morriond EWK conference.
By Loïc Quertenmont on March 21, 2014
CP3 turned 10 on November 5 !
By Juan Cabrera on November 4, 2013
We heartly congratulate Professors François Englert and Peter Higgs for the 2013 Nobel Prize in Physics. We are especially happy for our Belgian colleague François and all our colleagues from ULB.

CMS and ATLAS independently announced the discovery of a new particle on 4 July 2012, later identified as a Higgs boson, confirming the predictions of Professors Brout, Englert and Higgs in seminal papers published in 1964.
By Christophe Delaere on October 8, 2013
The 2013 High Energy and Particle Physics Prize of the European Physical Society has been awarded jointly to the ATLAS and CMS collaborations for the discovery of a new heavy particle with the properties of the long-sought Higgs boson, and to three experimental physicists, Michel Della Negra (CERN, now at Imperial College London, UK), Peter Jenni (CERN, now at Univ. of Freiburg, DE) and Tejinder Virdee (Imperial College London, UK) for their pioneering and outstanding leadership rôles in the making of the ATLAS and CMS experiments.
By Christophe Delaere on August 1, 2013
As it has been the case since more than 10 years, Ph.D. students in high energy particle physics from CP3 brought the future physicist generation at CERN in the context of their first lecture in particle physics. In March, students in their third year in physics had indeed a unique opportunity to visit CERN and the various experiments done there. Follow the link for more details.
By Claude Nuttens on April 3, 2013
The anisotropies of the Cosmic microwave background (CMB) as observed by Planck. The CMB is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380 000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today.
By Christophe Ringeval on March 25, 2013
This year again, we open internship positions in experimental high energy physics. These positions are open to BAC3 and Master (1 and 2) students. The exact topics will be chosen is agreement with the selected candidates, and may range from computing and analysis methods to instrumentation, in either the CMS or NA62 collaborations. For master students, a stay at CERN is possible.

Interested? Apply online!
By Christophe Delaere on March 18, 2013
One year and a half after the first (and fully performed at CP3) measurement of exclusive processes at the LHC, four CP3 members made first ever observation of W pair production via photon fusion. As a consequence, it allowed to push the best limits on anomalous quartic couplings by two orders of magnitude. Finally, this ensured excellent perspectives for CMS toward further studies of the electroweak sector of the Standard Model using the two-photon processes.
By Laurent Forthomme on February 19, 2013
On November, 22 and 23, Belgian physicists gathered in CP3 for a mini-workshop dedicated to Higgs search efforts in Belgium.
On Thursday, we discussed the implications of the recent results presented at the HCP conference in Japan, both from a theoretical and experimental perspective. The session on Friday was restricted to the CMS collaboration, with an emphasis on synergies among the different Belgian groups.
By Christophe Delaere on November 27, 2012
Friday, October 19, a vast majority of CP3 was present at our (so far annual) outing day. We had planed to probe an extra dimension, leaving terra firma to explore the third dimension in a course in the trees.
By Christophe Delaere on October 25, 2012
Fabio Maltoni received this prestigious mandate for the coming three years! This is also good news for CP3 since this mandate will allow him to have less teaching duties and therefore more time dedicated to research and collaborations within CP3 and beyond. Congratulation indeed!
By Vincent Lemaitre on August 28, 2012
In a joint seminar on July 4th at CERN and the “ICHEP 2012” conference in Melbourne, researchers of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) presented their preliminary results on the search for the standard model (SM) Higgs boson in their data recorded up to June 2012.
CMS observes an excess of events at a mass of approximately 125 GeV with a statistical significance of five standard deviations (5 sigma above background expectations.
This was retransmitted in CP3 and followed by a Q&A session.
By Christophe Delaere on July 4, 2012
On Monday June 24th, Vincent Lemaître was elected as new director of CP3, at the first round of votes. It happens as CP3 is more lively than ever, with 13 faculty, 14 post-docs and twice as many PhD students.
Among other challenges, Vincent will have to work on the integration of the centre in the new administrative structures of UCLouvain.

Many thanks to Jean-Marc Gérard, present director and future president of the IRMP institute, and best wishes to Vincent for the next three years.

Picture: About 1/2 of CP3 gathered in front of the building.
By Christophe Delaere on June 27, 2012
The CMS collaboration just submitted for publication the study of the production of b jets in association with a Z/gamma* boson, study to which members of CP3 played a leading role. This is an important step towards understanding the background to a potential light Higgs boson decaying into pairs of b quarks.
By Christophe Delaere on April 11, 2012
CMS preliminary results, exclude the existence of the Standard Model (SM) Higgs boson in a wide range of possible Higgs boson masses: 127 – 600 GeV at 95% confidence level. Compared to the SM prediction there is an excess of events in the mass region around 125GeV, that appears, quite consistently, in five independent channels. The excess is most compatible with an SM Higgs hypothesis in the vicinity of 124 GeV and below, but with a statistical significance of less than 2 standard deviations (2σ) from the known backgrounds, once the so-called Look-Elsewhere Effect has been taken into account.
By Christophe Delaere on December 14, 2011
Three CP3 members made a novel study at the LHC. For the first time, the measurement of exclusive production of muon pairs has been performed in very demanding conditions of high event pileup (i.e. multiple interactions in one beam crossing). This opens the way for an original and precise luminosity measurement, as well as for unique studies of the high energy photon interactions at the LHC.
By Nicolas Schul on June 28, 2011
CP3 members contributed another prime measurement at LHC, with the early observation of the Z+b process at LHC. For the first time, the Z+bb candidates are also presented. This preliminary result is being shown at "Moriond 2011", the most important Winter conference in High Energy Physics.
By Christophe Delaere on March 22, 2011
After the first top-quark pair production cross section in November'10, CP3 contributes again to a first cross section measurement at 7 TeV, this time of single-top production in t-channel. This preliminary result is being shown at "Moriond 2011", the most important Winter conference in High Energy Physics. [Update, March 15]: article on Symmetry Magazine.
By Andrea Giammanco on March 13, 2011
The CMS paper "Search for Heavy Stable Charged Particles in pp collisions at sqrt(s)=7 TeV" has been accepted for publication by JHEP. This is an almost 100% CP3 paper. Only 3 papers before this one have been published by CMS (2100 authors) on searches for new physics.
By Giacomo Bruno on February 17, 2011
The plot demonstrating the capability of CMS of identifying particles via the ionization energy loss measurement, fully developed by CP3 members, stands alone on the cover of the last issue of the European Physical Journal C
By Giacomo Bruno on November 23, 2010
Madgraph predictions on the production of W boson accompanied with jets match proton collision data taken by CMS at the LHC (CERN).
By Fabio Maltoni on September 30, 2010

The CMS Collaboration at CERN released a paper entitled “Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions” that details signs of a new phenomenon in proton interactions.

A study of “high multiplicity” collisions, where a hundred or more charged particles are produced, has revealed indications that some particles are somehow “correlated” – associated together when they were created at the point of collision.

It was considered natural to search for these correlations in the highest multiplicity proton-proton collisions at LHC as the particle densities begin to approach those in high-energy collisions of nuclei such as copper, where similar effects have already been seen...

By Christophe Delaere on September 23, 2010
Among the results presented by the CMS collaboration at ICHEP 2010, most important Summer conference in High Energy Physics, the first top quark candidate events at 7 TeV (shown in Figure: a dileptonic event with two secondary vertices attributed to the decays of b quarks) and an improved exclusion of long-lived gluinos as well as a measurement of the CMS Tracker material. CP3 gave a strong contribution to these achievements.
By Andrea Giammanco on July 30, 2010
The New Scientist magazine features research from C. Ringeval, T. Suyama (UCLouvain) and T. Takahashi, M. Yamaguchi and S. Yokoyama from Japan about dark energy (preprint available from arXiV).

According to their model and current cosmological observations, inflation should occur at the TeV scale, i.e. precisely in the LHC search area.
By Christophe Ringeval on July 29, 2010

Contact : Jérôme de Favereau