Measurement of matter-antimatter differences in beauty baryon decays

meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as

C\!P

violation. Using data from the LHCb experiment at the Large Hadron Collider, a search is made for

C\!P

-violating asymmetries in the decay angle distributions of

\Lambda^0_b

baryons decaying to

p\pi^-\pi^+\pi^-

and

p\pi^-K^+K^-

final states. These four-body hadronic decays are a promising place to search for sources of

C\!P

violation both within and beyond the Standard Model of particle physics. We find evidence for

C\!P

violation in

\Lambda^0_b

to

p\pi^-\pi^+\pi^-

decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for

C\!P

violation in the baryon sector.

Note:

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-030.html

p p: scattering
p p: colliding beams
Lambda/b0: hadronic decay
meson: decay
CP: violation
asymmetry: CP
parity: transformation
charge conjugation
CERN LHC Coll
statistical

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