The baryon number and lepton number of a black hole
The baryon number is the number of baryons minus the number of antibaryons. (Here on Earth this usually turns out to be the number of protons minus the number of antiprotons plus the number of neutrons minus the number of antineutrons.)
The lepton number is the number of electrons minus the number of positrons plus the number of neutrinos minus the number of antineutrinos.
By example a Helium-4 atom: 2 protons and 2 neutrons in the nucleus and 2 electrons circling around it. The baryon number of the He-4 atom is 4, the lepton number is 2.
For convenience we shall take that baryon numbers as well as lepton number always add, particles have positive numbers while antiparticles have negative numbers for the baryon and lepton numbers. This is precisely the same rule, only defined in a little different way.
Take a star collapsing to a black hole. First the star passes the stage of a neutron star: all electrons are pushed into the protons and in doing so turning them to neutrons. For every electron that is absorbed by a proton an electron neutrino is given back to the universe in stead of the electron, to conserve lepton number. The electron neutrinos escape the star. The baryon number of the neutron star is equal to the total number of neutrons in it, the lepton number of the star is zero (provided the neutron star is not electrically charged). This is what is going to to collapse to a black hole, providing mass is sufficiently large.
The neutrons spoil the picture I want to sketch. Let's get rid of them by a thought experiment. A gamma ray is directed to every neutron on the surface of the neutron star and gives the neutron sufficient energy to split in a proton and an electron and an anti electron neutrino. The anti electron neutrinos escape the neutron star. The proton is free now, the energy of the gamma ray was sufficient to release it and give it a small velocity to stay free for a (not too) small amount of time. One electron combines with the proton to form a H-atom. Soon all of the neutron star is converted into a cloud of single hydrogen atoms. I assume this resembles the primordial cloud where the former neutron star did originate from. Let this cloud be the matter that is going to collapse to a black hole. The baryon number of the cloud is the number of protons, the lepton number of the cloud is the number of electrons. The lepton number is equal to the baryon number now, provided the black hole has no net electric charge.
The Hawking radiation of the black hole, that finally will evaporate it entirely, consists of photons, most of the time from very long wave radiation. Photons have baryon number zero and lepton number zero.
So one star mass of an equal amount of baryons and leptons is converted by Hawking radiation in photons of lepton number zero and baryon number zero. How our black holes does do that? Is there e.g. a change there can be fumbled at the baryon number and lepton number of the photon?
As long as the black hole mass is still high, it radiates only very low energy photons. These photons can be observed from a frame of reference moving with very high speed opposite to that of the photons, so that by Doppler effect the photon from the black hole has enough energy for the reaction
photon e- e+ (e- = electron, e+ = positron)
The lepton number of the right side of the equation is
1 - 1 = 0
The law of the conservation of lepton number says the lepton numbers of the right side and of the left side are equal, so the photon definitely has lepton number zero.
We can give our frame of reference from which we observe the Hawking radiation a still higher velocity, in order to give the Hawking radiation photons energy for the reaction
photon p+ p- (p+ = proton, p- = antiproton)
The baryon number of the right side of the equation is
1 - 1 = 0
The law of the conservation of baryon number says the baryon numbers of the right side and of the left side are equal, so the photon definitely has baryon number zero too.
So no, there cannot be tampered with the baryon or lepton number of the photon, both will stay zero.
There is another possibility. TONE, my theory of gravitation and of nuclear colors as quaternions, suggests the electron is a spin half particle with color white or black, that is quaternion value 1 or -1 respectively. In TONE electrons are supposed to be quarks with color white or black, colors that don't glue. Then electrons are a kind of baryons, you may add the baryon and lepton numbers to one combined baryon lepton number.
We stick to the rule that particles have positive baryon number or positive lepton number. While antiparticles always have negative baryon number or negative lepton number. IF the electron happened to be the antiparticle and so has color -1, THEN its lepton number is -1. Then the combined baryon-plus-lepton number of our black hole will be zero. And this is in concordance with the zero baryon and lepton numbers of the Hawking radiation into which the black hole finally will evaporate. See more about this in page 4 of QUATERNION GRAVITATION.