- Mar 1st, 2014 by Alma Ionescu
Don
Lincoln is now a senior physicist at Fermi National Accelerator
Laboratory and splits his research time studying data from the Fermilab
Tevatron and from the CERN Large Hadron Collider, located outside Geneva
Switzerland.
He is co-author of over 500 scientific publications that range over subjects from microscopic black holes and extra dimensions to the elusive Higgs boson. His two most noteworthy scientific accomplishments include being part of the teams that discovered the top quark and what is likely to be the Higgs boson.
When Dr. Lincoln isn’t exploring the energy frontier, he enjoys communicating the excitement of his cutting edge research with the public. He is a popular writer because of his ability to explain fundamental particle physics in a deeply meaningful way and because of his fine sense of humor. So far he published two books which have been translated into Polish, Russian, German and Chinese. “Understanding the Universe: From Quarks to the Cosmos” and “The Quantum Frontier: The Large Hadron Collider” explain particle physics for the public. His third book (Alien Universe: Extraterrestrials in our Minds and in the Cosmos) combines astrobiology and popular reports of alien visitation to weave together a complete tale of the possibility of life from other planets.
His fourth book, which is due out in the summer of 2014, tells the tumultuous story of the startup of the Large Hadron Collider and the saga of the discovery of the Higgs boson. It also includes an extended description of supersymmetry and the reasons that physicists have long felt that it would be observed at the LHC. Even more interesting, he tells us some of the theories that might be right if it turns out that supersymmetry isn't to be found.
In June 2014, Dr. Lincoln will teach a course on the "Mysteries of the Universe" for Scientific American
Professional Learning about the most burning topics in today's physics. Bright Horizons 23 (end of November
2014) is another event that he is preparing with Scientific American Travel for those interested in science.
Q: How does life look like for an American physicist working in big science?
So that’s me. I’m a senior American physicist. I’ve risen to the highest regular academic level in the US university/laboratory system (full professor). I have coauthored over 500 scientific papers. I have written a handful of books and articles in magazines like Scientific American. I discovered the Higgs boson. (Well, me and 6,000 of my closest personal friends.) I also discovered the top quark. (This time, it only took 800 of us.) I also give a ton of public lectures and make videos about physics, aimed at the general public.
So keep that in mind as you read my answer. As a senior experimental particle physicist who works in the ultra-huge collaborations necessary to work at the Large Hadron Collider, I have a certain perspective. If you asked someone who was a physicist at a smaller academic institution who did theoretical work, or a person who worked in industry, you’d get a somewhat different answer. But this answer is free…so here goes.
If you want to do physics for a living, the first and most important advice is to really, really, really want to do physics. It is written somewhere that the number of our years is between threescore and ten and fourscore if you are lucky. There are many ways to spend those few short years: chasing fame or fortune, helping others who are less fortunate, rising high in a corporate structure or politics, devoting one’s life to military endeavors, or simply just finding a shady tree so you can sit and watch nature. If none of those things appeals to you as much as spending your time confused and figuratively pounding your head against the wall, trying to figure out the rules of the universe, well then maybe a career in science is what you want.
Q: Some scientists have added supersymmetry to the Standard Model and we know you’re looking for proof of this theory at the LHC. Why is SUSY needed?
First, supersymmetry is not a theory. It is a principle that a theory has. You can see a video on what this means here. I also made a second video that alludes to the reason physicists like supersymmetry, here. This second video tells very briefly some of the reasons for which supersymmetry is theoretically-popular, but it doesn’t describe the theory in enough detail to understand the story very well. For that, I can point to an article I wrote about why is the Higgs so light here.
Q: Is there an easy way to understand this principle?
I can describe the whole situation here very briefly. In essence, we don’t understand why the mass of the Higgs boson is so low. According to the standard model, the Higg’s boson mass should be incredibly high. The reason is quantum mechanics. According to the Heisenberg uncertainty principle, the Higgs boson can briefly convert into other particles before converting back to a single Higgs bosons. The most common particles into which it can convert are top quarks, W & Z bosons, and pairs of Higgs bosons.
Because of the fraction of time that the Higgs boson is acting like other particles, this drives the predicted mass of the Higgs boson to very high values. While the actual equation is far more complicated, the contribution to the mass of the Higgs boson due to quantum mechanics has the following form:
has to be awfully close to zero. And that’s just kind of weird. Why should those particles balance out so perfectly? Further, if you use the right equation and put in the measured numbers, you see it doesn’t work.
The real equation for the Higgs boson is
Q: So, is the standard model wrong?
Well…yes. And no. It’s certainly incomplete and that’s where supersymmetry comes in. If you watched the videos, you’ll recall that one of the consequences of supersymmetry is that it predicts for every known particle there is another cousin particle. So for a top quark, there is a supersymmetric cousin called the top squark. And for the W, Z and H bosons, there are the cousins Winos, Zinos and Higgsinos. If these cousins exist, then they also participate in the quantum mechanics of Higgs bosons and that modifies the second term in the equation to be:
Q: That is why SUSY is so popular among theoretical physicists?
Yes, that’s why supersymmetry is so popular. If you add supersymmetry to the standard model, you can explain why the mass of the Higgs boson is so low.
Q: What does it take to make a career in physics?
Since we’re all friends here, I’m going to tell you a secret. But I’ll deny ever saying it, so don’t repeat it. So here’s the secret: Even if you are scientifically-inclined, there are lots of different mind-bending scientific problems. There is the mind. There is the origin of life and our human species. There are fascinating medical problems and trying to understand weather and the climate. The number of cool and interesting questions is countless.
However, if you’re the kind of kid who kept asking “why” until your parents ran out of answers (or patience), well then you may be one of those people like me who is a physicist. You want to know the answer to the deep and fundamental questions…like why the physical world is the way it is. If you’re not such a person, you should stop reading now; because the rest of this essay will bore you to tears.
OK…now that we’ve gotten rid of all of those unenlightened people, let’s talk about physics as a career. The path you take depends crucially on the country in which you live. I can’t cover all countries, so I’ll tell you the story of an American. It may be that you have already received some education and you’ll have to decide where you could slip into the US education system.
In the US, we go to school for 12 years. The last four years is called high school and it is there that we begin to differentiate ourselves. For a person who is going to be a physicist, it is important to take as much math as possible. You should at least take precalculus and if your school teaches calculus, take it. (If it doesn’t, don’t worry. You can take calculus in college.) You should take chemistry, biology and physics. You should take your English seriously…knowing how to write well is important. If you can somehow learn to program computers, that’s just totally awesome…go for it.
You then go to a university for four years. (In the US, we don’t distinguish a college and a university like other countries do.) During that time, you learn a lot of things, but this is where you focus on physics. I’d caution you to not focus too much on a particular subdiscipline. If you like quantum mechanics, maybe take an extra class on the subject, but don’t neglect the breadth of physics. Learn classical mechanics and electromagnetism. Learn about solid state physics and astronomy and statistical mechanics. Dabble in special relativity and if you can get a survey class in general relativity, all the better. The goal of university education in physics is to have a good grounding in the basics.
Q: Where does research fit into all this and how does that help later on?
While you are studying for your bachelor’s degree (i.e. four year university degree), it is pretty important that you do some research. It can be theoretical or experimental. At this age, many people aspire to being a theorist; after all, our heroes are Albert Einstein and we hear about the accomplishments of Bohr and Heisenberg and Planck. But there is a downside to theory. More on that later. In the meantime, do some research. That’s my first bit of important advice. It will make getting into a good graduate school much easier.
When you go to college, you go into debt. An inexpensive university is about 20,000 USD/year and an expensive one can be 50,000 USD. That is a lot of money. But there is a nice thing with being a physicist. After the first four years, the money thing gets a lot easier.
Once you graduate with a bachelor’s degree, you move on to graduate school. Here’s the first good news. Graduate school is not only free, you can actually get paid to go. (Take that medicine and law!) So here’s my second bit of important advice: go to the most prestigious graduate school you can get into. If you can get into Berkeley, do it. Caltech? Great! Columbia? You bet. There is a long list of good schools and you should try to pick one.
Now if you don’t get into a super high-end school, that’s not the end of your career. I went to Rice University for graduate school. It’s a perfectly-good, second tier school. I ended up being a scientist working on the Large Hadron Collider. It worked out. However it would have been easier if I went to a higher end university. I didn’t know how much it helps… but it does.
Q: Speaking of research, the LHC still obtained no trace of supersymmetry even at much higher collision energy. Is that something that worries physicists?
The answer to the worry is “no.” But the story is more complex than this. Now if we don’t find supersymmetry at the LHC, all that really means is that supersymmetry doesn’t solve the mystery of the Higgs boson mass. Supersymmetry could still exist at even higher energies…energies higher than the LHC can see.
However, if we don’t see it at the LHC, then supersymmetry doesn’t answer the mystery of the mass of the Higgs boson and this means that there must be something else that is the answer to that question. Either way, we should find something at the LHC…either supersymmetry or something else. That’s why the LHC is such an interesting machine to use to do research. It’s almost guaranteed that something new will be found.
Q: What would you recommend to students if they were to choose between quantum or mathematical physics?
So with all this information, we can come to answering the question “quantum or mathematical physics?” The answer is, of course, well it’s a lot more complicated than that.
You don’t have to decide this before you get to graduate school, although knowing what you want to do means it is easier to make a good decision what school to go to. If you are certain you want to do quantum, pick a school with an amazing program in quantum. This is true of any program. But most people don’t know exactly what they want to do. For people like that, it’s better to go to a bigger university. The reason is that there are professors doing many different types of physics. You can change your direction if you want.
Q: So what are the realities of this choice?
The realities are that if you want to stay in physics for your whole life, you need to get a faculty job and work at a university. These jobs are hard to come by. Something like 1% of the people who go into physics go on to being a professor at a big university. The odds are higher for people doing experimental work and lower if you do theoretical work. In my field of particle physics, there might be 8 professor positions each year in the entire US. Most of them are experimental physicist faculty positions and a few are theoretical ones. There might be one theoretical physicist faculty position in the entire country in a year… and some years there are none.
So should these daunting odds keep you out of physics? Well, no. Remember that you’re one of those people who want to understand the universe. While you are in college and graduate school, you’ll learn a bunch. And if you are one of those people who leave physics and go into industry, you can make a ton of money.
Q: As a summary, what should readers take home as to what it is like to pursue a career in this field?
There’s so much more one can say about a career in physics, but let me close with some useful facts.
Don Lincoln received his Ph.D. in experimental particle physics from Rice University. He has published many magazine articles in periodicals that include Analog: Science Fiction and Fact, The Physics Teacher and Scientific American. If you count all the magazines that have been printed, his writing has appeared well over a million times.
He has given hundreds of lectures on four continents. He enjoys speaking to a broad range of audiences, but his favorite kind of audience are non-scientists who are interested in understanding how the world works. He has a series of YouTube videos that explain frontier physics to a lay audience and he is a blogger for the NOVA television show on PBS. He also writes a weekly column for the online periodical Fermilab Today, which popularizes research papers as they are released.
The Higgs field, explained
What is antimatter?
How does an atom smashing particle accelerator work?
*Editor's note:
(based on Particle Data Group values)
W mass ~ 80.4 GeV/c2.
Z mass ~ 91.2 GeV/c2.
H mass ~ 125.9 GeV/c2.
Top mass ~ 173.07 GeV/c2
The subtraction will yield a difference of roughly 124.43 GeV/c2, i.e. the terms don't cancel out. Notice that in the last expression where the super-partners are inserted, the terms anticommute and cancel out.
Don
Lincoln is now a senior physicist at Fermi National Accelerator
Laboratory and splits his research time studying data from the Fermilab
Tevatron and from the CERN Large Hadron Collider, located outside Geneva
Switzerland. He is co-author of over 500 scientific publications that range over subjects from microscopic black holes and extra dimensions to the elusive Higgs boson. His two most noteworthy scientific accomplishments include being part of the teams that discovered the top quark and what is likely to be the Higgs boson.
When Dr. Lincoln isn’t exploring the energy frontier, he enjoys communicating the excitement of his cutting edge research with the public. He is a popular writer because of his ability to explain fundamental particle physics in a deeply meaningful way and because of his fine sense of humor. So far he published two books which have been translated into Polish, Russian, German and Chinese. “Understanding the Universe: From Quarks to the Cosmos” and “The Quantum Frontier: The Large Hadron Collider” explain particle physics for the public. His third book (Alien Universe: Extraterrestrials in our Minds and in the Cosmos) combines astrobiology and popular reports of alien visitation to weave together a complete tale of the possibility of life from other planets.
His fourth book, which is due out in the summer of 2014, tells the tumultuous story of the startup of the Large Hadron Collider and the saga of the discovery of the Higgs boson. It also includes an extended description of supersymmetry and the reasons that physicists have long felt that it would be observed at the LHC. Even more interesting, he tells us some of the theories that might be right if it turns out that supersymmetry isn't to be found.
In June 2014, Dr. Lincoln will teach a course on the "Mysteries of the Universe" for Scientific American
Professional Learning about the most burning topics in today's physics. Bright Horizons 23 (end of November
2014) is another event that he is preparing with Scientific American Travel for those interested in science.
Q: How does life look like for an American physicist working in big science?
So that’s me. I’m a senior American physicist. I’ve risen to the highest regular academic level in the US university/laboratory system (full professor). I have coauthored over 500 scientific papers. I have written a handful of books and articles in magazines like Scientific American. I discovered the Higgs boson. (Well, me and 6,000 of my closest personal friends.) I also discovered the top quark. (This time, it only took 800 of us.) I also give a ton of public lectures and make videos about physics, aimed at the general public.
So keep that in mind as you read my answer. As a senior experimental particle physicist who works in the ultra-huge collaborations necessary to work at the Large Hadron Collider, I have a certain perspective. If you asked someone who was a physicist at a smaller academic institution who did theoretical work, or a person who worked in industry, you’d get a somewhat different answer. But this answer is free…so here goes.
If you want to do physics for a living, the first and most important advice is to really, really, really want to do physics. It is written somewhere that the number of our years is between threescore and ten and fourscore if you are lucky. There are many ways to spend those few short years: chasing fame or fortune, helping others who are less fortunate, rising high in a corporate structure or politics, devoting one’s life to military endeavors, or simply just finding a shady tree so you can sit and watch nature. If none of those things appeals to you as much as spending your time confused and figuratively pounding your head against the wall, trying to figure out the rules of the universe, well then maybe a career in science is what you want.
Q: Some scientists have added supersymmetry to the Standard Model and we know you’re looking for proof of this theory at the LHC. Why is SUSY needed?
First, supersymmetry is not a theory. It is a principle that a theory has. You can see a video on what this means here. I also made a second video that alludes to the reason physicists like supersymmetry, here. This second video tells very briefly some of the reasons for which supersymmetry is theoretically-popular, but it doesn’t describe the theory in enough detail to understand the story very well. For that, I can point to an article I wrote about why is the Higgs so light here.
Q: Is there an easy way to understand this principle?
I can describe the whole situation here very briefly. In essence, we don’t understand why the mass of the Higgs boson is so low. According to the standard model, the Higg’s boson mass should be incredibly high. The reason is quantum mechanics. According to the Heisenberg uncertainty principle, the Higgs boson can briefly convert into other particles before converting back to a single Higgs bosons. The most common particles into which it can convert are top quarks, W & Z bosons, and pairs of Higgs bosons.
Because of the fraction of time that the Higgs boson is acting like other particles, this drives the predicted mass of the Higgs boson to very high values. While the actual equation is far more complicated, the contribution to the mass of the Higgs boson due to quantum mechanics has the following form:
[Highest energy for which the standard model applies] x [(mass of W, Z & Higgs bosons) – (mass of top quarks)]
Note that the real equation has some squared terms and integers floating around. Don’t worry about those and just look at the basic structure. Remember that the highest energy for which the standard model is thought to apply is 1019 GeV. Further, that first term is actually squared, so it really is 1038 GeV2. So we can write that equation as
1038 x [(W, Z, H boson) – (top quark)] *
Since the Higgs boson has a mass of only 125 GeV, we can see that the first number is just way too huge…somehow that second term
[(W, Z, H boson) – (top quark)]
has to be awfully close to zero. And that’s just kind of weird. Why should those particles balance out so perfectly? Further, if you use the right equation and put in the measured numbers, you see it doesn’t work.
The real equation for the Higgs boson is
Mass(Higgs, observed)2 = Mass(Higgs, theoretical)2 + [k L]2 × [Mass(Z boson)2 + 2 × Mass(W boson)2 +Mass(Higgs, observed)2 – 4 × Mass(top quark)2]
where k is a constant and L is the Planck energy, the maximum energy that the theory applies to. Notice the squares and the 2 and 4 in the second term. The equality does not hold.
Q: So, is the standard model wrong?
Well…yes. And no. It’s certainly incomplete and that’s where supersymmetry comes in. If you watched the videos, you’ll recall that one of the consequences of supersymmetry is that it predicts for every known particle there is another cousin particle. So for a top quark, there is a supersymmetric cousin called the top squark. And for the W, Z and H bosons, there are the cousins Winos, Zinos and Higgsinos. If these cousins exist, then they also participate in the quantum mechanics of Higgs bosons and that modifies the second term in the equation to be:
[(W, Z, H boson, top squark) – (Wino, Zino, Higgsino, top quark)]
And, if that happens, this term is equal to zero, each term cancelling with its superpartner: the W and the Wino, the top quark with the top squark and so on. If you're wondering why the funny names, this is the naming convention. The bosonic superpartners have the -ino suffix and the fermionic superpartners have the s- prefix.
Q: That is why SUSY is so popular among theoretical physicists?
Yes, that’s why supersymmetry is so popular. If you add supersymmetry to the standard model, you can explain why the mass of the Higgs boson is so low.
Q: What does it take to make a career in physics?
Since we’re all friends here, I’m going to tell you a secret. But I’ll deny ever saying it, so don’t repeat it. So here’s the secret: Even if you are scientifically-inclined, there are lots of different mind-bending scientific problems. There is the mind. There is the origin of life and our human species. There are fascinating medical problems and trying to understand weather and the climate. The number of cool and interesting questions is countless.
However, if you’re the kind of kid who kept asking “why” until your parents ran out of answers (or patience), well then you may be one of those people like me who is a physicist. You want to know the answer to the deep and fundamental questions…like why the physical world is the way it is. If you’re not such a person, you should stop reading now; because the rest of this essay will bore you to tears.
OK…now that we’ve gotten rid of all of those unenlightened people, let’s talk about physics as a career. The path you take depends crucially on the country in which you live. I can’t cover all countries, so I’ll tell you the story of an American. It may be that you have already received some education and you’ll have to decide where you could slip into the US education system.
In the US, we go to school for 12 years. The last four years is called high school and it is there that we begin to differentiate ourselves. For a person who is going to be a physicist, it is important to take as much math as possible. You should at least take precalculus and if your school teaches calculus, take it. (If it doesn’t, don’t worry. You can take calculus in college.) You should take chemistry, biology and physics. You should take your English seriously…knowing how to write well is important. If you can somehow learn to program computers, that’s just totally awesome…go for it.
You then go to a university for four years. (In the US, we don’t distinguish a college and a university like other countries do.) During that time, you learn a lot of things, but this is where you focus on physics. I’d caution you to not focus too much on a particular subdiscipline. If you like quantum mechanics, maybe take an extra class on the subject, but don’t neglect the breadth of physics. Learn classical mechanics and electromagnetism. Learn about solid state physics and astronomy and statistical mechanics. Dabble in special relativity and if you can get a survey class in general relativity, all the better. The goal of university education in physics is to have a good grounding in the basics.
Q: Where does research fit into all this and how does that help later on?
While you are studying for your bachelor’s degree (i.e. four year university degree), it is pretty important that you do some research. It can be theoretical or experimental. At this age, many people aspire to being a theorist; after all, our heroes are Albert Einstein and we hear about the accomplishments of Bohr and Heisenberg and Planck. But there is a downside to theory. More on that later. In the meantime, do some research. That’s my first bit of important advice. It will make getting into a good graduate school much easier.
When you go to college, you go into debt. An inexpensive university is about 20,000 USD/year and an expensive one can be 50,000 USD. That is a lot of money. But there is a nice thing with being a physicist. After the first four years, the money thing gets a lot easier.
Once you graduate with a bachelor’s degree, you move on to graduate school. Here’s the first good news. Graduate school is not only free, you can actually get paid to go. (Take that medicine and law!) So here’s my second bit of important advice: go to the most prestigious graduate school you can get into. If you can get into Berkeley, do it. Caltech? Great! Columbia? You bet. There is a long list of good schools and you should try to pick one.
Now if you don’t get into a super high-end school, that’s not the end of your career. I went to Rice University for graduate school. It’s a perfectly-good, second tier school. I ended up being a scientist working on the Large Hadron Collider. It worked out. However it would have been easier if I went to a higher end university. I didn’t know how much it helps… but it does.
Q: Speaking of research, the LHC still obtained no trace of supersymmetry even at much higher collision energy. Is that something that worries physicists?
The answer to the worry is “no.” But the story is more complex than this. Now if we don’t find supersymmetry at the LHC, all that really means is that supersymmetry doesn’t solve the mystery of the Higgs boson mass. Supersymmetry could still exist at even higher energies…energies higher than the LHC can see.
However, if we don’t see it at the LHC, then supersymmetry doesn’t answer the mystery of the mass of the Higgs boson and this means that there must be something else that is the answer to that question. Either way, we should find something at the LHC…either supersymmetry or something else. That’s why the LHC is such an interesting machine to use to do research. It’s almost guaranteed that something new will be found.
Q: What would you recommend to students if they were to choose between quantum or mathematical physics?
So with all this information, we can come to answering the question “quantum or mathematical physics?” The answer is, of course, well it’s a lot more complicated than that.
You don’t have to decide this before you get to graduate school, although knowing what you want to do means it is easier to make a good decision what school to go to. If you are certain you want to do quantum, pick a school with an amazing program in quantum. This is true of any program. But most people don’t know exactly what they want to do. For people like that, it’s better to go to a bigger university. The reason is that there are professors doing many different types of physics. You can change your direction if you want.
Q: So what are the realities of this choice?
The realities are that if you want to stay in physics for your whole life, you need to get a faculty job and work at a university. These jobs are hard to come by. Something like 1% of the people who go into physics go on to being a professor at a big university. The odds are higher for people doing experimental work and lower if you do theoretical work. In my field of particle physics, there might be 8 professor positions each year in the entire US. Most of them are experimental physicist faculty positions and a few are theoretical ones. There might be one theoretical physicist faculty position in the entire country in a year… and some years there are none.
So should these daunting odds keep you out of physics? Well, no. Remember that you’re one of those people who want to understand the universe. While you are in college and graduate school, you’ll learn a bunch. And if you are one of those people who leave physics and go into industry, you can make a ton of money.
Q: As a summary, what should readers take home as to what it is like to pursue a career in this field?
There’s so much more one can say about a career in physics, but let me close with some useful facts.
- People doing experimental physics are more likely to be able to make a career of physics than theorists.
- The types of physics that have the most positions (academic and university) are solid state and optics.
- No matter how cool it is to argue about relativity and the Copenhagen Interpretation of quantum mechanics, nobody gets a faculty position on such things.
- If you really like quantum mechanics, quantum cryptography and quantum computing are hot topics.
- When I was a kid, if you wanted to do cosmology, it was mostly a theoretical endeavor. But now it has become an experimental field. That’s pretty cool.
- The most awesome physics you can do is experimental particle physics and cosmology. That’s just my opinion of course, but I’m writing this. If you disagree, get your own blog.
- It’s pretty hard to stay in physics for your whole life. Try to have a backup plan that interests you just as much. And most people who leave physics are smart and energetic and find fascinating things to do. Leaving research is only a failure if you’re not open to other experiences.
- Finally, learning is just totally cool. Follow your passion. If you love what you are doing, all the difficulties are OK.
Don Lincoln received his Ph.D. in experimental particle physics from Rice University. He has published many magazine articles in periodicals that include Analog: Science Fiction and Fact, The Physics Teacher and Scientific American. If you count all the magazines that have been printed, his writing has appeared well over a million times.
He has given hundreds of lectures on four continents. He enjoys speaking to a broad range of audiences, but his favorite kind of audience are non-scientists who are interested in understanding how the world works. He has a series of YouTube videos that explain frontier physics to a lay audience and he is a blogger for the NOVA television show on PBS. He also writes a weekly column for the online periodical Fermilab Today, which popularizes research papers as they are released.
You can follow Dr. Lincoln at http://www.facebook.com/Dr.Don.Lincoln
Watch Dr. Don Lincoln's videos:
What is a Higgs Boson?
The Higgs field, explained
What is antimatter?
How does an atom smashing particle accelerator work?
*Editor's note:
(based on Particle Data Group values)
W mass ~ 80.4 GeV/c2.
Z mass ~ 91.2 GeV/c2.
H mass ~ 125.9 GeV/c2.
Top mass ~ 173.07 GeV/c2
The subtraction will yield a difference of roughly 124.43 GeV/c2, i.e. the terms don't cancel out. Notice that in the last expression where the super-partners are inserted, the terms anticommute and cancel out.
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