First observation of forward <math altimg='si1.gif' overflow='scroll'><mi>Z</mi><mo stretchy='false'>→</mo><mi>b</mi><mover accent='true'><mrow><mi>b</mi></mrow><mrow><mo stretchy='false'>¯</mo></mrow

The decay <span class="math"><math><mi is="true">Z</mi><mo stretchy="false" is="true">→</mo><mi is="true">b</mi><mover accent="true" is="true"><mrow is="true"><mi is="true">b</mi></mrow><mrow is="true"><mo stretchy="false" is="true">¯</mo></mrow></mover></math></span> is reconstructed in <em>pp</em> collision data, corresponding to 2 fb^-1 of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of <span class="math"><math><msqrt is="true"><mrow is="true"><mi is="true">s</mi></mrow></msqrt><mo is="true">=</mo><mn is="true">8</mn></math></span> TeV. The product of the <em>Z</em> production cross-section and the <span class="math"><math><mi is="true">Z</mi><mo stretchy="false" is="true">→</mo><mi is="true">b</mi><mover accent="true" is="true"><mrow is="true"><mi is="true">b</mi></mrow><mrow is="true"><mo stretchy="false" is="true">¯</mo></mrow></mover></math></span> branching fraction is measured for candidates in the fiducial region defined by two particle-level <em>b</em>-quark jets with pseudorapidities in the range <span class="math"><math><mn is="true">2.2</mn><mo is="true">&lt;</mo><mi is="true">η</mi><mo is="true">&lt;</mo><mn is="true">4.2</mn></math></span>, with transverse momenta <span class="math"><math><msub is="true"><mrow is="true"><mi is="true">p</mi></mrow><mrow is="true"><mi mathvariant="normal" is="true">T</mi></mrow></msub><mo is="true">&gt;</mo><mn is="true">20</mn></math></span> GeV and dijet invariant mass in the range <span class="math"><math><mn is="true">45</mn><mo is="true">&lt;</mo><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><mi is="true">j</mi><mi is="true">j</mi></mrow></msub><mo is="true">&lt;</mo><mn is="true">165</mn></math></span> GeV. From a signal yield of <span class="math"><math><mn is="true">5462</mn><mo is="true">±</mo><mn is="true">763</mn></math></span> <span class="math"><math><mi is="true">Z</mi><mo stretchy="false" is="true">→</mo><mi is="true">b</mi><mov. Authors: Aaij, R.; Adeva, B.; Adinolfi, M.; Ajaltouni, Z.; Akar, S.. DOE Contract: AC02-05CH11231. Subjects: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS