# New physics searches with charm decays at LHCb

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

### Abstract

The goal of particle physics is to understand the fundamental building blocks of the universe and the rules by which they play. Some of these fundamental particles can be studied in nature---for example, all of the matter on earth is made from two kinds of quark (assembled into protons and neutrons) plus electrons. The nuclear furnace at the heart of the sun spits out immense numbers of neutrinos. Still other, rarer particles arrive in cosmic showers. All of the particles that we have found in nature, plus others that we have been able to produce in super-colliders, are described by a theory known as the Standard Model. This is a venerable theory that has stood, largely unmodified, since the 1970s. However, more and more evidence is piling up that the Standard Model is incomplete---that it is a good approximation but is missing some vital pieces, just as Newton's laws of motion were nearly right most of the time but were superseded by Einstein's theory of relativity. There are many aspects of the universe that the Standard Model does not explain, such as why matter is so much more common than anti-matter, or the nature of dark matter and dark energy (which together make up 95% of the universe!), or even gravity itself. There are also problems of internal consistency in the model. Many of these problems point to something new, exciting, and not at all understood just over the horizon; we simply call this 'new physics'. One powerful way to grapple with this is to look for things that the Standard Model says are impossible, but which are plausible with new physics. Then, if you see the supposedly impossible effect, you learn immediately that the Standard Model is wrong and---even more valuable---how it went wrong. If you don't see anything, that is still useful information: models of new physics now have to explain why the effect is not allowed, pinning them down. In this project, we will study a specific kind of particle known as charmed mesons. These particles are made from one charm quark and one light antiquark. They also have an antiparticle, made from one charm antiquark and one light quark. Both kinds are unstable, but can live for long enough to travel a fraction of a centimeter. In the Standard Model, there is a virtually perfect mirror symmetry between the two: they live for the same amount of time on average, they decay in equivalent ways, and so on. With new physics, though, this symmetry can be broken. The effect is very slight, so we need to study enormous numbers of particles to see it. We will do this with the data recorded by the LHCb detector at the Large Hadron Collider, which will begin operation in 2008. LHCb will record hundreds of millions of charm meson decays, a vastly larger sample than we've had access to before. By sifting through this data, we hope to find this slight discrepancy, break open the Standard Model, and finally uncover the new physics that lies beyond.

### ORCID iD

Matthew John Charles (Principal Investigator / Fellow)  http://orcid.org/0000-0003-4795-498X

### Publications

10 25 50

Aaij R (2012) Observation of excited ?(b)(0) baryons. in Physical review letters

Aaij R (2012) Measurement of b-hadron masses in Physics Letters B

Aaij R (2013) Exclusive J /? and ?(2 S ) production in pp collisions at $\protect \sqrt{s} = 7$ TeV in Journal of Physics G: Nuclear and Particle Physics

Description The aim of the research project was to search for, and hopefully find, evidence of new, as-yet-undiscovered physics beyond our Standard Model of particle physics. Using the very large data samples of charmed particles recorded by the LHCb detector in its first years of operation, we published several world-leading searches for new physics effects, using a variety of signatures. We also published other results aimed at helping us understand the Standard Model and the LHCb physics environment. While we were not lucky enough to make a breakthrough discovery, the research advanced our collective understanding of charm physics.
Exploitation Route We made measurements (or placed limits on) several observables related to charm physics. These results have already been used by other physicists to improve the world-average values for certain parameters, helping to constrain models of new physics beyond the Standard Model. The research also showcased novel methods, some of which (notably the Delta A_CP approach) have now been widely adopted in the subdomain.
Sectors Education,Other

Description Results have been used in outreach and reported in the media, notably the 2011 Delta A_CP paper.
First Year Of Impact 2011
Sector Education
Impact Types Cultural

Description Programa de Capacitacao Institucional (PCI) -- travel grant
Amount £4,092 (GBP)
Organisation Brazilian Center for Physics Research (CBPF)
Sector Public
Country Brazil
Start 04/2011
End 04/2011

Description BABAR
Organisation Stanford University
Department BaBar Experiment
Country United States
PI Contribution Analysis; analysis infrastructure (e.g. internal review)
Impact Numerous publications, preliminary results, and conference talks on which I am a named author. Several publications for which I am a primary author.
Start Year 2008

Description LHCb
Organisation European Organization for Nuclear Research (CERN)
Department Large Hadron Collider Beauty Experiment (LHCb)
Country Switzerland
Sector Public
PI Contribution Contributions to analysis and analysis infrastructure; detector operations (shifts and piquets); management role (co-convenor of analysis sub-group)
Impact Numerous publications, preliminary results, and conference talks on which I am a named author. Several publications for which I am a primary author.
Start Year 2008

Description SiD/PFA
Organisation Rutherford Appleton Laboratory
Department Space Science and Technology Department
Country United Kingdom
PI Contribution Consultative support of ongoing research / algorithm development.
Collaborator Contribution Collaboration on algorithm development/support (low-level)
Impact SiD letter of intent; LCWS conference talk and proceedings; ongoing algorithm development (e.g. as presented at LCWS11)
Start Year 2008

Description SiD/PFA
Organisation University of Iowa
Department Department of Physics and Astronomy
Country United States
PI Contribution Consultative support of ongoing research / algorithm development.
Collaborator Contribution Collaboration on algorithm development/support (low-level)
Impact SiD letter of intent; LCWS conference talk and proceedings; ongoing algorithm development (e.g. as presented at LCWS11)
Start Year 2008

Description All About Space (Giles Sparrow)
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Short piece (200 words) written by me appeared in the UK popular science magazine "All about Space".

Impact not evaluated.
Year(s) Of Engagement Activity 2013

Description BBC Focus Magazine (Daniel Cossins)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Phone interview with journalist formed the basis for a magazine article in "BBC Focus".

Impact not evaluated.
Year(s) Of Engagement Activity 2011

Description BBC website (Jason Palmer)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Phone interview with journalist formed the basis for an article on the BBC website.

http://www.bbc.co.uk/news/science-environment-15734668

Impact not evaluated.
Year(s) Of Engagement Activity 2011

Description CF 2010
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Audience of 10-15 at sci-fi convention, mostly student-age. Questions and discussion during and after presentation. No media presence.

Not practical to evaluate impact.
Year(s) Of Engagement Activity 2010

Description LiveScience.com (Clara Moskowitz)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Phone interview with journalist formed the basis for a web article on livescience.com.

http://www.livescience.com/17093-lhc-antimatter-particle-physics.html

Impact not evaluated.
Year(s) Of Engagement Activity 2011

Description Science (Jon Cartwright)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Email interview with journalist formed the basis for an article in "Science Now".

http://news.sciencemag.org/sciencenow/2011/11/particle-smasher-hints-at-physic.html

Impact not evaluated.
Year(s) Of Engagement Activity 2011

Description Science News (Devin Powell)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Phone interview for an article in "Science News" magazine.

Impact not evaluated.
Year(s) Of Engagement Activity 2011

Description Sunday Times (Jonathan Leake)
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Phone interview with journalist fed into an article in The Sunday Times.

Impact not evaluated.
Year(s) Of Engagement Activity 2011